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The Potential Impact of Blood System on Dietary Habits and Smoking

Ioannis tsamesidis.

1 Department of Biomedical Sciences, International Hellenic University, 57001 Thessaloniki, Greece; moc.liamg@repmilve

2 School of Dentistry, Faculty of Health Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece

Evangelia Stalika

3 Lab of Computing and Medical Informatics, Medical School, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; [email protected]

Chinedu O. Egwu

4 PharmaDev, UMR 152, Université de Toulouse, IRD, UPS, 31000 Toulouse, France; moc.oohay@0102yajohce

Agathi Pritsa

5 Department of Nutritional Sciences and Dietetics, International Hellenic University, 57001 Thessaloniki, Greece; rg.ehtiet.rtun@astirpga

Maria Parpori

6 Department of Nursing, International Hellenic University, 57001 Thessaloniki, Greece; moc.liamtoh@prpairam

Argyrios Gkinoudis

7 School of Veterinary Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; moc.liamg@asiduonig

Diana Samara

8 Blood Bank Section, Naoussa General Hospital, 59200 Naousa, Greece; moc.liamg@7aramasanaid

Evgenia Lymperaki

Associated data.

Data is contained within the article.

The ‘Blood-Type’ diet advises individuals to eat according to their ABO blood group to improve their health and decrease the risk of chronic diseases. However, the food preferences of individuals with different blood groups have not been examined. The aim of our study was to investigate, in healthy regular blood donors (rBDs), the associations of smoke, alcohol, caffeine, vitamin and fat intake with their different blood groups and if ABO groups could be a potential predictor tool for disease prevention. A total of 329 volunteers were divided into four groups according to their ABO types: Group 1 (A) comprised 141 rBDs; Group 2 (B), 65 rBDs; Group 3 (O), 96 rBDs; and Group 4, 27 rBDs. Additionally, they were divided into two groups according to their rhesus types and their preferences for smoke, too. Dietary intake was assessed using 3-day food recall and the Food Processor computer program for nutrient analysis. Alcohol, caffeine, sugar and Vitamin D consumption were significantly ( p < 0.05) higher in the O group. The A group presented statistically significantly ( p < 0.05) greater preferences for cholesterol intake and a higher trend for smoking (25%) habits compared with all the other groups, whereas Group B preferred more fatty foods. The blood group AB appeared to be the most controlled food intake group. Regarding the rhesus comparisons, alcohol; caffeine; and Vitamin C, D, E and K consumptions were significantly ( p < 0.05) higher in rhesus-positive individuals than their rhesus-negative counterparts. For the non-smoker group, compared with the smokers, a higher consumption of Vitamin D and fibers was found. In conclusion, in the present study, statistically significant correlations of the ABO and rhesus system with some dietary parameters were found, indicating a consequent influence of these preferences on the progression of different diseases.

1. Introduction

ABO blood grouping is one of the first genetic variations recognized in humans and has since been linked to several health conditions. Since the publication of the book “ Eat Right for Your Type” by D’Adamo [ 1 ], there has been a series of debates for and against the correlation of an individual’s ABO blood group, eating habits and health. This theory considers our ancestral dietary habits and suggested that adherence to diets specific to one’s blood type can reduce the risk of cardiovascular disease and improve health generally [ 1 ]. The most common food preferences comprise caffeine, alcohol, fruits, and vegetables containing vitamins and fats. Caffeine is a nutrient that can be found in many beverages and plays an important role in health because of its interference in Vitamin B and essential mineral absorption [ 2 ]; moreover, in low doses, besides producing an increase in mental energy and attention, and elevated mood, it also has antioxidant properties [ 3 ]. Vitamins, and especially Vitamins A and D, have a crucial effect on the regulation of immune responses and have a protective role in inflammation and autoimmunity. They participate in the production of specific antibodies, the proliferation of lymphocytes, and T cell differentiation [ 4 ].

Wang et al. demonstrated that, although adhering to some blood-type diets may reduce cardiometabolic risk factors, these links are independent of an individual’s ABO group [ 5 ]. On the other hand, research on the ABO group system proposed an association between ABO blood groups and a variety of diseases such as hepatitis [ 6 ], thrombotic disorders [ 7 ], metabolic and cardiovascular diseases [ 8 , 9 ], cognitive disorders and circulatory diseases. Moreover, AB individuals were found to be linked with an increased incidence of smallpox, E. coli and Salmonella infections [ 10 ]. Additionally, the blood type O presents a connection with an increased incidence of cholera, plague and tuberculosis infections, whereas the blood type A seems to be linked with an increased incidence of Pseudomonas aeruginosa infection [ 10 ]. Additionally, the ABO blood system has been verified to be linked with the severity of some infectious diseases such as malaria for the B group [ 11 , 12 , 13 ] and COVID-19 for the A group [ 14 , 15 , 16 ]. In the literature, a few studies have demonstrated the analysis of dietary habits as well as smoking to investigate the possible association with the blood group system. In the past, studies to demonstrate the association of smoking with ABO blood groups were conducted, without significant results [ 17 , 18 , 19 ]. In a cohort study, Jaleel et al. demonstrated that people having tobacco-chewing habits with blood group A were at a 1.46-times greater risk of developing oral cancer, compared with those of blood groups B, AB and O [ 17 ]. Regarding eating habits, according to Leite et al., one’s ABO blood group affects one’s tastes and preferences [ 20 ]. The blood group antigens are differentially expressed in the sensory cells of the auditory, taste and olfactory systems. The results of a cohort study demonstrated that the ability to recognize phenylthiocarbamide (PTC) in a taste test is related to blood group B and a high risk of developing food allergies; however there is no consensus on whether this actually affects taste in individuals with different ABO groups [ 21 , 22 , 23 ]. Additionally, there are a few reports of the association of the O blood group and addiction to alcohol and opioids [ 24 , 25 ]; however, there is no consensus on the exact correlation between ABO groups and addiction/preferences. Moreover, Raman et al. demonstrated the effect of plant lectins on human blood group binding activity, indicating that the O blood group showed the most significant activity compared with other blood groups [ 26 ]. The growing association of diseases with ABO blood groups and the paucity of evidence linking ABO groups and tastes/preferences call for an intensified effort in understanding the correlation between diet and health conditions in individuals with varying ABO statuses. This work, therefore, aimed to investigate the associations and trends of the smoke, alcohol, caffeine, vitamin and fat intake of healthy regular blood donors (rBDs) with their blood groups.

2. Materials and Methods

2.1. study design.

A pilot study was carried out at the Blood Bank of Naousa Hospital, Greece. The blood donors (n = 329) comprised 182 males aged 19–61 years and 147 females aged 21–64 years. All the participants provided written informed consent before the study and were asked to fill out a short questionnaire about sociodemographic characteristics such as the age, sex, body mass index (BMI), smoking habits and residence of the blood donors. All the volunteer regular blood donors (rBDs) were selected, recognizing them as a healthy population, excluding drug and supplement intake.

2.2. Dietary Intake (DI) Assessment

A 3-day food recall (one weekend day and two weekdays) was used to estimate the dietary intake. All the participants were asked to describe, in detail, the quantity and type of food consumed during those 3 days. The 3-day dietary intake recalls were conducted in face-to face interviews by experienced nurses and dietitians of the hospital. Written and verbal instructions were provided in order to complete their food recalls. Dietary intake was assessed using the Food Processor computer program for nutrient analysis (ESHA, Salem, OR, USA, 2010) (version 7.4) with Greek foods, as previously performed [ 27 ]. The study mainly used the Greek food composition in the EuroFIR AISBL e-book collection by the Hellenic Health Foundation to convert dietary data to nutrient intakes [ 28 ].

2.3. AΒO Blood and Rhesus System Detection

Just before blood donation, the A, B, O and AB groups and rhesus statuses were obtained for all the participants from the Blood Bank in General Hospital in Naousa using the Ortho Biovue clinical diagnostics system.

2.4. Ethical Statement

The study was conducted in accordance with Good Clinical Practice guidelines and the Declaration of Helsinki. Ethical approval to perform the present study was obtained from the Ethical Committee of the General Hospital of Naousa (ID_233205920). The confidentiality of the participants was wholly preserved.

2.5. Statistical Analysis

To compare biochemical markers with the ABO blood group and rhesus type, statistical analysis was performed using the SPSS tool version 22.0. Descriptive statistics, presented as the mean ± standard deviation, were performed. Additionally, inferential statistical analysis ( t -test) was used for investigating the possible differences between two blood groups regarding the biochemical markers’ statuses. One-way ANOVA tests further evaluated possible differences in the lipidemic and anemic predispositions among the blood groups. In all the statistical analysis, the level of significance ( p -value) was set at α = 0.05. The independent variables with p < 0.05 in bivariate correlation analysis were enrolled in binary logistic regression for further analysis. A logistic regression model was used to examine the effect of particular independent variables on different ABO blood groups.

3. Results and Discussion

The distributions of the blood groups across the different subpopulations in our study are presented in Table 1 . The study population was selected based on the inclusion criteria outlined in the methodology. Demographic analysis of the 329 donors showed 60%, 45%, 50% and 50% males for A, B, O and AB, respectively. The ABO blood group frequencies in the Greek population revealed A as the most frequent, followed by O, B and AB, respectively, in accordance with other regional studies [ 29 , 30 ]. The BMI levels of all the rBDs did not present any significant differences.

Characteristics of all study participants.

Correlations between ABO blood group smoking and dietary intakes in study population are presented in Table 2 . For the entire study population, alcohol, caffeine and sugar consumption were significantly ( p < 0.05) higher in the O group. In addition to several intervening factors, the taste of alcohol and other beverages may also influence the highest consumption of blood group O without necessarily promoting disease generation [ 31 ]. Moreover, Vitamin D consumption was higher, too, confirming its relationship with COVID-19 [ 32 ] and their in-between correlation [ 15 ]. The A group presented significantly ( p < 0.05) greater preferences for cholesterol and fiber intake and a higher trend for smoking (25%) habits compared with all the other groups. This fact is in accordance with other studies [ 8 , 33 ] related to the association of the A blood type with a high risk of cardiovascular diseases. On the other hand, the intakes of vitamins, such as Vitamins A and C, was higher in blood group A, indicating their health benefits in developing a dietary balance. All the rBDs followed a traditional Mediterranean diet based on the Greek food pyramid guidelines. The food pyramid is divided into three levels of consumption: the daily consumption of wholegrain cereals and products, fruits, vegetables and olive oil; secondly, the weekly consumption of fish, poultry, olives, pulses, nuts, potatoes, eggs and sweets; and monthly, red meat.

Correlation between ABO blood group smoking and dietary intakes in study population. Statistically significant differences are presented with *.

Nordmo demonstrated a significant association between blood group A and alcoholism; however, this claim may have been limited by the shortcomings of the research, which included sampling errors [ 34 , 35 ]. Meanwhile, those with blood group B preferred more fatty foods, confirming the observations of other investigations indicating that the rate of hypertension for the blood type B is the maximum, compared with the other blood groups [ 36 , 37 ]. The blood group AB appears to show the most controlled food intake overall, indicating that the blood type AB is protective for hyperlipidemia and other common diseases, too.

The impact of rhesus factors on the consumption of different diets is presented in Table 3 . For the study population, the alcohol; caffeine; and Vitamin C, D, E and K consumptions were significantly ( p < 0.05) higher in rhesus-positive individuals than their rhesus-negative counterparts. Cholesterol consumption was also significantly higher among rhesus-positive individuals than their rhesus-negative counterparts. Rhesus factor status did not significantly ( p > 0.05) affect the consumption of Vitamin A, Ω3, Ω6, fiber and sugar. In the same vein, there was no statistical ( p > 0.05) difference in the consumption of fat and different types of fat (sat.fat, MUFA and PUFA) between rhesus-positive and rhesus-negative individuals in the population studied. Rhesus factor is a type of protein present on the surface of red blood cells, and its presence (rhesus positive) or absence (rhesus negative) can trigger different types of reactions to different diets. Rhesus-negative individuals are prone to more immunoglobulin E allergies than rhesus-positive individuals [ 38 ]. Different diets trigger IgE differently. The reported differences in responses could be due to the differences in IgE triggers in these individuals with either rhesus-positive or negative status. The fear of allergic reactions, which could be life threatening in some cases, may influence the choice of a particular type of food.

Correlation between rhesus types and preferences in study population. Statistically significant differences are presented with *.

Smokers are an important target group for dietary intervention, and their preferences should be evaluated in order to analyze their eating patterns for this reason; the preferences of the smokers and non-smokers in the study population are presented in Table 4 . There was no in-between group difference in the consumption of alcohol; caffeine; cholesterol; and Vitamins C, E, K and A; however, for Vitamin D, the consumption was significantly higher in non-smokers than in smokers. The consumption of Ω3 was also similar in both groups, while for Ω6 and sugar, it was higher in non-smokers. For fiber, non-smokers showed statistically significant greater preferences compared with the smokers ( p = 0.001). The consumption of fat and the different types of fat (saturated fat and PUFA) were generally similar in both groups, except for MUFA, known as the healthier fat, which was significantly higher in non-smokers. Our data and previous analysis [ 39 , 40 ] in smokers and non-smokers revealed that the non-smokers were following healthier dietary consumptions compared with the smokers. Although there were no significant in-between group differences for most diets (except for Ω6, sugar, fiber, MUFA and Vitamin D), it has been previously reported that cigarette smokers have more difficulties in controlling different cravings [ 41 ].

Correlation of smokers and non-smokers with preferences in study population. Statistically significant differences are presented with *.

4. Conclusions

Previous reports have provided some evidence for associations between dietary intakes and the ABO blood system. In the present population, we found statistically significant correlations of the ABO and rhesus system with some dietary parameters, which are also associated with certain diseases and their in-between correlations with the blood system. Food preferences can influence the risks of different diseases without certainly being the exact cause of diseases. Moreover, the health community and the medical nutritionists should take into consideration the blood system as an important factor before planning a diet. Further studies in a larger population and in different ethnicities will provide more insights into the role of the blood system in diet and disease progression.

Author Contributions

Conceptualization: E.L. and I.T.; methodology: I.T., E.L. and D.S.; formal analysis: I.T., E.L., E.S., M.P., A.P., A.G., C.O.E.; investigation: I.T. and E.L.; resources: E.L. and D.S.; writing—original draft preparation: I.T., E.L. and C.O.E.; writing—review and editing: E.L. and I.T.; supervision: I.T. and E.L. All authors have read and agreed to the published version of the manuscript.

Funding not received for the study.

Institutional Review Board Statement

The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Ethics Committee of General Hospital of Naousa (ID 233205920).

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

Conflicts of interest.

The authors declare no conflict of interest.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Are 'Blood Type Diets' Actually Rooted In Any Science?

There is a lot of speculative science from the man who invented the diet, but actual evidence in support of the diet’s efficacy is severely lacking., alex kasprak, published dec. 9, 2016.

About this rating

In 1996, naturopathic doctor Peter D’Adamo published the book Eat Right For Your Type, which presented the hypothesis that diet, exercise, and lifestyle changes tailored to one’s blood type are an effective tool for weight loss, increased energy, and the reduction of myriad other ailments. This has popularly become known as the "blood type diet", for which he is the primary proponent.

D’Adamo’s website provides this description :

A naturopathic physician who is also an author, researcher-educator, Ivesian, amateur horologist, budding software developer and air-cooled enthusiast. He is considered a world expert in glycobiology, principally the ABO (ABH) blood groups and the secretor (FUT2) polymorphisms.

Since its original publication, Eat Right For Your Type has sold over seven million copies, has been promoted by popular (but scientifically unreliable) health personalities like Dr. Oz and has created an entire industry built around the diet, including a series of follow up-books, cookbooks, a variety of blood tests for sale, and other supplements.

There are many different ways to classify blood types, but the most common (and the primary one D’Adamo employs) is the ABO system, which is determined by the presence or absence of two genetically regulated antigens – A and B – attached to the surface of red blood cells. The four blood type groups are A, B, AB, and O.

Superficially, there might appear to be a wealth of complex, technical, and well-documented support for the concept. In addition to his popular books, D’Adamo has written numerous detailed blog posts describing how blood types might affect the body.

Much of the rationale presented on his website fits the following basic structure: there’s a study that shows or hints at various conditions correlating with blood type, therefore a diet tailored to blood type would be more helpful than a general one.

To date, however, no peer-reviewed scientific literature has provided any evidence to support the latter class of arguments. This is a point D’Amado himself cedes. In response to a 2014 study in PLOS ONE that was highly critical of his work, he stated (17 years after first publishing his book):

That the [blood type diet] theory is currently unproven by rigorous scientific study is not argued. Hopefully in time this can be rectified by studies which accurately and comprehensively prove or disprove the hypothesis.

In lieu of accurate and comprehensive studies that prove or disprove his hypotheses, D’Adamo’s basic rationale is rooted primarily in four observations listed on his website:

First, that people with different blood types appear to have differing susceptibility to a variety of illnesses; second, that people with different blood types produce and degrade differing amounts of the stress related hormones cortisol or adrenaline; third, that the antigens that determine your blood type are found in other places besides your blood; and fourth, that that blood type has a strong influence on an individual's gut bacteria.

There are indeed varying levels of scientific basis for the above claims. That blood antigens are found in the tissue of multiple systems is not controversial . A 2013 review paper on the relationship between disease and blood type published in the journal Blood Transfusion concluded:

There is accumulating evidence that the ABO blood group also plays a key role in various human diseases such as cardiovascular, neoplastic and infectious disorders. In the near future, probably many of the statistical associations observed between ABO and diseases will be re-assessed by [genome-wide association studies]. These studies have already confirmed some of the relations detected by targeted researches carried out long before the current era of genomics, such as those with [venous thromboembolism], [coronary heart disease], and pancreatic cancer.

With respect to blood type and stress hormones (which play a big role in his lifestyle and exercise recommendations), D’Adamo cites a limited 1992 study of 15 white male veterans published in the journal Psychosomatic Medicine that showed differences in the production and removal of cortisone in A and O blood types.

The gut bacteria connection is one of the most prominent aspects of his theory. Studies have indeed observed differences in the relative contribution of gut bacteria based on blood type. A 2012 study published in BMC Microbiology that analyzed the gut flora and blood type of 79 Finnish volunteers found:

That the ABO blood group is one of the genetically determined host factors modulating the composition of the human intestinal microbiota, thus enabling new applications in the field of personalized nutrition and medicine.

Much of the dietary recommendations for the blood type diet are based on the concept of eating foods your body is naturally better at handling, as stated on D’Adamo’s website :

For example, the microbiome of certain people developed to break down carbohydrates much more efficiently (blood type A). People lacking this ability (blood type O) tend to store carbs as fat.

Another key diet/blood connection promoted by D’Adamo stems from lectins — a group of proteins found in many foods — which he argues can mimic different blood-type antigens, and “interact” with your kidneys, liver, gut, stomach, or other organ systems:

For the most part our immune systems protect us from lectins. Ninety-five percent of the lectins we absorb from our typical diets are sloughed off by the body. But at least 5 percent of the lectins we eat are filtered into the bloodstream, where they react with and destroy red and white blood cells. The actions of lectins in the digestive tract can be even more powerful. There they often create a violent inflammation of the sensitive mucous of the intestines, and this agglutinative action may mimic food allergies. Even a minute quantity of a lectin is capable of agglutinating a huge number of cells if the particular blood type is reactive.

There are independent scientific reports of potential ways that lectins might interact with different bodily systems to cause disease as described above, but no peer-reviewed research directly tests a potential link between those phenomena and the claim that a blood type based diet would ameliorate any of those potential mechanisms.

A final aspect of D’Adamo’s blood type diet is the additional classification of a person’s “secretor/non-secretor status”. This is a classification independent of ABO blood type and refers to a person's genetically-determined ability to secrete blood type antigens into your saliva or mucus. In a 2001 paper in Alternative Medicine Reviews , he argued that this classification could have sweeping implications for human health:

Understanding the clinical significance of ABH secretor status and the Lewis blood groups can provide insight into seemingly unrelated aspects of physiology, including variations in intestinal alkaline phosphatase activity, propensities toward blood clotting, reliability of some tumor markers, the composition of breast milk, and several generalized aspects of the immune function.

The information summarized above provides a broad outline of the most commonly promoted scientific rationale for the blood-type diet, though there are pages and pages more written by D’Adamo on the topic. In essence there are a number of “seemingly unrelated” facts about blood that could, maybe, respond to different diet and exercise regimens.

A followup series of books published by D’Adamo included a different book for each ailment that he believed his diet might improve. Included in this series: arthritis, diabetes, cancer, cardiovascular disease, allergies, fatigue, menopause, and aging.

The only problem is that there is literally no evidence demonstrating his ideas work, and D’Adamo himself doesn’t appear to be super interested in producing that evidence. In 1996, in the first edition of Eat Right For Your Type , D’Amato wrote :

Even now, as I write this, I am beginning the eighth year of a ten-year trial on reproductive cancers, using the Blood Type Diets. My results are encouraging. So far, the women in my trial have double the survival rate published by the American Cancer Society. By the time I release the results in another two years, I expect to make it scientifically demonstrable that the Blood Type Diet plays a role in cancer remission.

Such a study has yet to be released. On his website, D’Adamo has a section for scientific papers that support the science behind the diet. Nearly all of these self-authored papers are from the late 80s and early 90s, or are more recent blog posts written by D’Adamo.

With the exception of that 2001 paper mentioned earlier, the only scientific papers he has published are either in the long defunct (but allegedly peer-reviewed) journal the Townsend Letter for Doctors (which frequently published studies on the efficacy of homeopathy ), and the Journal of Naturopathic Medicine , which no longer exists and is not catalogued in any major scientific or medical journal index.

There have, however, been a few peer-reviewed studies that sought to test some aspects of the blood-type diet.

The first was a 2013 literature review published in the American Journal of Clinical Nutrition that sought to find any existing, statistically rigorous research showing that tailoring diet to blood type has a beneficial effect.   The effort yielded only 16 studies, and of these only one met their standards for inclusion. Further, that study didn’t actually address the question of whether or not blood-type diets themselves were efficacious. The authors of this literature review conclude :

No evidence currently exists to validate the purported health benefits of blood type diets. To validate these claims, studies are required that compare the health outcomes between participants adhering to a particular blood type diet (experimental group) and participants continuing a standard diet (control group) within a particular blood type population.

D’Adamo argued in a blog post that the absence of papers should not be surprising, given the cutting-edge and novel nature of his then 17-year-old hypothesis:

Not surprisingly, they didn’t find any. Had they contacted me prior to the study I could have saved them a lot of extra work. I’ve looked high and low and also never found one. That’s how original this theory is.

A 2014 study published in the journal PLOS ONE attempted to provide novel research into the claims of the blood-type diet by analyzing the results of a larger scale nutrition study that utilized 1,455 subjects who “were participants of the Toronto Nutrigenomics and Health study” and whose “dietary intake was assessed using a one-month, 196-item food frequency questionnaire and a diet score was calculated to determine relative adherence to each of the four ‘Blood-Type’ diets.’”

That study concluded that, while individuals who adhered to any one of the four different blood-type diets did have favorable health benefits, there was no relationship between blood type and those favorable effects. According to a University of Toronto press release :

“Based on the data of 1,455 study participants, we found no evidence to support the 'blood-type' diet theory," said the senior author of the study, Dr. Ahmed El-Sohemy, Associate Professor and Canada Research Chair in Nutrigenomics at the U of T. "The way an individual responds to any one of these diets has absolutely nothing to do with their blood type and has everything to do with their ability to stick to a sensible vegetarian or low-carbohydrate diet," said El-Sohemy.

D’Adamo has subsequently published a number of blog posts criticizing the study for not accurately following the prescribed blood type diet while simultaneously celebrating the fact that the diet (in general) helped people lose weight and improve health. Ahmed El-Sohemy, the lead researcher behind the PLOS ONE study, has composed detailed responses to each of these posts in the comments section, if you want an illuminating read .

D’Adamo is certainly prolific, both in his numerous blogs and in his library of best selling books. Lost within that sea of complex jargon, speculative observations, and anecdotal tales, however, is the fact that there is no widely accepted or peer-reviewed evidence that modifying one’s diet to match blood type has any effect on one's health.

D’Adamo, Peter, J.   Eat Right 4 Your Type .     Penguin, 1997.   1101042788

dadamo.com .   "Dr. Peter J. D'Adamo."

Wang, Jingzhou, et al.   "ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors."     Plos One .   15 January 2014.

redcrossblood.org .   "Blood Types."

dadamo.com .   "Science Writings/ Software by Dr. Peter D'Adamo"

dadamo.com .   "What went wrong with the The PLOS 'Blood Type Diet' Study?"

dadamo.com .   "Blood Type and Your Health."

Szulman, Aron E.   "The Histological Distribution of Blood Group Substances A and B in Man."     Journal of Experimental Medicine .   1 June 1960.

Liumbruno, Giancarlo, and Franchini, Mariaand Massimo.   "Beyond Immunohaematology: the Role of the ABO Blood Group in Human Diseases."     Blood Transfusion .   October 2013.

Neumann, JK, et al.   "Effects of Stress and Blood Type on Cortisol and VLDL Toxicity Preventing Activity."     Psychosomatic Medicine .   September 1992.

Mäkivuokko, Hari.   “Association Between the ABO Blood Group and the Human Intestinal Microbiota Composition."     BMC Microbiology .   6 June 2012.

dadamo.com .   "The Lectin Connection"

Freed, David, L.   "Do Dietary Lectins Cause Disease?"     BMJ .   18 April 1999.

Jaff, Mohamad Salih.   "Higher Frequency of Secretor Phenotype in O Blood Group – Its Benefits in Prevention And/or Treatment of Some Diseases."     International Journal of Nanomedicine .   2 November 2010.

Cusack, Leila.   "Blood Type Diets Lack Supporting Evidence: A Systematic Review."     The American Journal of Clinical Nutrition .   22 May 2013.

D’Adamo, Peter.   "Gnomic Advice."     http://n-equals-one.com/ .   3 June 2013.

University of Toronto .   "Popular Blood Type Diet Debunked."     15 January 2014.

D’Adamo, Peter.   "Kicking Bubbles."     n-equals-one.com/   24 January 2014.

D’Adamo, Peter.   "Unbelievable Facts"     n-equals-one.com   17 January 2014.

By Alex Kasprak

Alex Kasprak is an investigative journalist and science writer reporting on scientific misinformation, online fraud, and financial crime.

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What Do You Eat on the Blood Type Diet?

• Blood Type Diet Theory
• Proposed Benefits
• Considerations
• Dietary Restrictions

The blood type diet is the basis of a book published in 1996 by naturopathic physician Peter D'Adamo. The book outlined suggestions for increasing health benefits by eating foods corresponding to your blood type . While the book was popular, the blood type diet is not backed by evidence, and its claims are not substantiated.

Blood type diet theory proposes that those with group A blood should eat a mostly vegetarian diet, those with group O should focus on high animal protein, and those with group B should eat dairy products. It recommends a diet that has elements of both the A and B diet for people with AB blood.

This article will discuss how the blood type diet is proposed to work, foods suggested by the diet for each blood group , if there are benefits for eating for your blood type, considerations, and dietary restrictions with a blood type diet.

Jordi Salas / Getty Images

How Is the Blood Type Diet Claimed to Work?

The major ABO blood group is based on determined by which antigens (substances that can trigger an immune response) are present on the surface of red blood cells. A antigen, B antigen, both, or neither may be present, resulting in the blood types A, B, AB, and O.

The blood type diet proposes that because of evolutionary history, blood type can affect how certain foods are digested. By extension, eating accordingly could provide health benefits.

The theory is that type O was the original "ancestral" blood type, meaning the blood type of the earliest humans. Based on the diets of early humans as hunter-gatherers, the diet claims people with this blood type are best suited to eating animal protein.

Theoretically, group A blood evolved when humans began to farm and consume a more vegetarian diet, and group B blood was developed among nomadic tribes who had a high consumption of dairy. The AB type formed through reproduction between people with type A and type B blood.

However, there is evidence that the first humans had blood types in addition to type O. Their close relatives (including Neanderthals) have types A, B, and O. In primates, types A and O are seen in chimpanzees, A and B in gorillas, and A, B, and AB in orangutans and gibbons.

Blood Types and Health

Older research from the 1950s and 1960s compared blood types for the risk of ischemic heart disease ( coronary artery disease ). People with type O blood had a modest reduction in risk compared to those with other blood types.

A 2016 meta-analysis of case-control and cohort studies found evidence that supported these earlier studies, with findings suggesting a 15% reduced risk of coronary artery disease (CAD) for blood group O.

Other studies have suggested that people with type A blood have an increased risk of higher total cholesterol and low-density lipoprotein (LDL) cholesterol (considered bad cholesterol) concentrations. Studies have found inconsistent relationships between blood types and the risk of type 2 diabetes .

These findings have prompted questions about whether a person could benefit from dietary choices tailored to their blood type. There is a lack of research on this subject, and the limited amount of observational data does not support the health benefits of eating based on blood type.

Blood Type O Foods 

According to the blood type diet theory, those with type O blood should eat:

• Meat (including red meat)
• Vegetables (such as broccoli and spinach)

They should limit:

For weight loss, they should avoid:

Blood Type A Foods 

The blood type diet theorizes that people with type A blood should eat:

• Whole grains

They should avoid red meat .

• Kidney beans

Blood Type B Foods

Following the blood type diet theory, those with type B blood should eat a diversity of foods, including:

• Green vegetables

Blood Type AB Foods

Blood type diet theorizes that people with type AB blood should eat:

Proposed Benefits of Eating Based on Your Blood Type 

Studies examining the blood type diet found that the dietary suggestions for type A (increased intake of fruits, vegetables, and grains ) did benefit those with type A blood, but they also benefited those with types O, B, and AB.

A 2014 study found that the different proposed eating plans had certain health effects, but these were not impacted by blood type. For example, a diet rich in vegetables, fruits, and whole grains that limits red meat, such as the type A recommendations, is associated with cardiovascular health benefits regardless of a person's blood type.

Similarly, the diet proposed for group AB, which advises limiting butter and eating eggs and fish as the main animal proteins, is associated with a more favorable cardiometabolic profile (tests for heart health and blood sugar management) than the type B plan, which has fewer restrictions on many animal products. These results applied to people of all blood types.

What Does the Research Say?

There is a lack of high-quality studies published in peer-reviewed medical literature on the blood type diet.

The main findings of existing studies examining the influence of blood type on diet and health benefits include:

• Health outcomes from the foods recommended for each blood type are related to the foods eaten, not the blood type, and are not unique to any blood type.
• Regardless of blood type, those whose eating patterns are similar to those outlined for the type A blood group (more fruit, vegetables, and grain, less meat) tend to have better cardio-metabolic (cardiovascular and metabolic) outcomes, such as lower body mass index (BMI) , waist circumference, serum cholesterol and triglyceride levels (fats in the blood), and insulin resistance (when cells in the body don't respond well to the hormone insulin and have difficulty taking up glucose from the blood, requiring more insulin).
• The type O diet recommendations (emphasizing meat, fruits, and vegetables and limiting grains) have been associated with lower triglyceride levels, regardless of the person's blood type.
• Evidence does not support using blood type as a basis for determining what foods to eat or avoid.

Considerations 

Health claims made by the blood type diet should be viewed as theoretical and not supported by scientific evidence.

Following an eating plan based on your current health concerns and family history makes more sense and has more research backing it. Eating plans such as the Mediterranean diet , the DASH (Dietary Approaches for Stopping Hypertension) diet, and certain anti-inflammatory diets have more substantial supporting evidence regarding health benefits.

Dietary Restrictions 

Following the recommendations for your blood type could be difficult with your dietary restrictions. For example, the type O recommendations that emphasize meat would go against the guidelines of a vegetarian or vegan eating pattern.

Talking to a registered dietitian can help you find evidence-based eating plans that fit your goals and lifestyle.

The blood type diet is based on a book that proposes eating foods tailored to your blood type could have health benefits, such as a mostly vegetarian diet for type A and an emphasis on animal protein for type O.

There is no quality evidence that blood type impacts dietary choices or that there is a benefit to choosing an eating plan based on blood group.

Any health benefits from eating according to the suggestions for each blood type apply to anyone who follows them regardless of blood type.

Instead of following a diet based on your blood type, it is advisable to choose evidence-based eating plans that address your health concerns, such as the DASH diet and/or talking to a registered dietitian.

Harvard Health. Diet not working? Maybe its not your type .

Wang J, García-Bailo B, Nielsen DE, El-Sohemy A. ABO genotype, ‘blood-type’ diet and cardiometabolic risk factors . Ashton N, ed. PLoS ONE . 2014;9(1):e84749. doi:10.1371/journal.pone.0084749

American National Red Cross. Facts about blood and blood types .

Condemi S, Mazières S, Faux P, Costedoat C, Ruiz-Linares A, Bailly P, Chiaroni J. Blood groups of Neandertals and Denisova decrypted . PLoS One . 2021;16(7):e0254175. doi:10.1371/journal.pone.0254175

Farhud DD, Zarif Yeganeh M. A brief history of human blood groups . Iran J Public Health . 2013;42(1):1-6.

Barnard ND, Rembert E, Freeman A, Bradshaw M, Holubkov R, Kahleova H. Blood type is not associated with changes in cardiometabolic outcomes in response to a plant-based dietary intervention . Journal of the Academy of Nutrition and Dietetics . 2021;121(6):1080-1086. doi:10.1016/j.jand.2020.08.079

Chen Z, Yang SH, Xu H, Li JJ. ABO blood group system and the coronary artery disease: an updated systematic review and meta-analysis . Sci Rep . 2016;6:23250. doi:10.1038/srep23250

Etemadi A, Kamangar F, Islami F, et al. Mortality and cancer in relation to ABO blood group phenotypes in the Golestan Cohort Study . BMC Med . 2015;13:8. doi:10.1186/s12916-014-0237-8

Lemaitre M, Passet M, Ghesquière L, Martin C, Drumez E, Subtil D, Vambergue A. Is the development of gestational diabetes associated with the ABO blood group/Rhesus phenotype? Front Endocrinol (Lausanne) . 2022;13:916903. doi:10.3389/fendo.2022.916903

Cusack L, De Buck E, Compernolle V, Vandekerckhove P. Blood type diets lack supporting evidence: a systematic review . The American Journal of Clinical Nutrition . 2013;98(1):99-104. doi:10.3945/ajcn.113.058693

Ohio State University Wexner Medical Center. Should you try the ‘blood type diet’?

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Does the ‘blood type diet’ work?

Registered Dietitian Ohio State Wexner Medical Center

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What if your blood type could determine exactly what foods to eat and which to avoid based on your unique body chemistry? That’s exactly what the blood type diet promises.

Naturopathic physician Peter J. D’Adamo created the blood type diet in 1996.

The idea behind the diet is that your blood type determines the best foods for you to eat, based on what your ancestors with the same blood type ate. So, what’s healthy for you may not be healthy for your partner.

Why eat according to your blood type?

The diet claims to help you lose weight , improve digestion and boost your overall well-being.

According to D’Adamo, each of the four blood types has its own guidelines about specific foods to eat and to avoid.

If you have:

• Type O blood eat largely a plant-based diet with plenty of lean meats and cut out wheat and dairy.
• Type A blood eat a vegetarian-based diet high in carbohydrates and cut out meat.
• Type B and type AB blood eat a balanced omnivorous diet.

Does the blood type diet work?

While the premise of the diet is intriguing, there’s not enough scientific evidence to support it. In fact, this diet has not been proven in any clinical trials. That means the blood type diet is only based on a theory by D’Adamo. None of the claims can be proven.

You could lose weight on the diet because it contains many foods — particularly fruits and vegetables  and lean meats — that are beneficial to your overall health. But that weight loss might not have anything to do with your eating foods in sync with your blood type.

People lose weight when they restrict calories. Since the blood type diet recommends avoiding highly processed foods such as desserts, chips and fast food, all of which contain a lot of calories, anyone may lose weight by avoiding these foods.

What is the best diet for weight loss?

As any dietitian will tell you, the key is to make a lifestyle change that includes meaningful dietary choices and continue them — not to follow a crash diet  for a few weeks and then revert.

I tend to steer people toward the Mediterranean diet  or a variation of it such as the DASH  (dietary approaches for stopping hypertension) as well as anti- inflammatory diets. These diets are roadmaps for healthy eating that include many plant-based foods, lean proteins and whole grains — all of which have been shown to benefit health.

Many of the foods in the Mediterranean and DASH diets are also in the blood type diet. That’s another reason people may be successful at losing weight on the blood type diet — because it includes so many nutrient-dense foods.

Family history over blood type

In choosing a diet, consider your current health concerns and your family history. For example, if you have a strong family history of high blood pressure, eating many fruits and vegetables high in potassium and magnesium while avoiding sodium is ideal. If you have high blood sugar or a family history of it, follow a diet moderate in carbohydrates and eat mostly complex carbohydrates that contain fiber, such as whole fruits, vegetables and whole grains.

It’s wisest to eat foods proven to benefit your specific health condition or family history.

As a registered dietitian, I’m always looking for what’s healthy — regardless of blood type. Eat mostly unprocessed and plant-based foods. That’s the foundation of a nutritious diet.

Healthy eating is within your reach!

Make an appointment with our dietitians or nutritionists.

Liz Weinandy, MPH, RDN, LD , is a registered dietitian at The Ohio State University Wexner Medical Center .

• Blood Type ,
• Healthy Eating ,
• Ohio State Wexner Medical Center ,
• Weight Loss ,
• Exercise and Nutrition

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ABO genotype, 'blood-type' diet and cardiometabolic risk factors

Affiliation.

• 1 Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
• PMID: 24454746
• PMCID: PMC3893150
• DOI: 10.1371/journal.pone.0084749

Background: The 'Blood-Type' diet advises individuals to eat according to their ABO blood group to improve their health and decrease risk of chronic diseases such as cardiovascular disease. However, the association between blood type-based dietary patterns and health outcomes has not been examined. The objective of this study was to determine the association between 'blood-type' diets and biomarkers of cardiometabolic health and whether an individual's ABO genotype modifies any associations.

Methods: Subjects (n = 1,455) were participants of the Toronto Nutrigenomics and Health study. Dietary intake was assessed using a one-month, 196-item food frequency questionnaire and a diet score was calculated to determine relative adherence to each of the four 'Blood-Type' diets. ABO blood group was determined by genotyping rs8176719 and rs8176746 in the ABO gene. ANCOVA, with age, sex, ethnicity, and energy intake as covariates, was used to compare cardiometabolic biomarkers across tertiles of each 'Blood-Type' diet score.

Results: Adherence to the Type-A diet was associated with lower BMI, waist circumference, blood pressure, serum cholesterol, triglycerides, insulin, HOMA-IR and HOMA-Beta (P<0.05). Adherence to the Type-AB diet was also associated with lower levels of these biomarkers (P<0.05), except for BMI and waist circumference. Adherence to the Type-O diet was associated with lower triglycerides (P<0.0001). Matching the 'Blood-Type' diets with the corresponding blood group did not change the effect size of any of these associations. No significant association was found for the Type-B diet.

Conclusions: Adherence to certain 'Blood-Type' diets is associated with favorable effects on some cardiometabolic risk factors, but these associations were independent of an individual's ABO genotype, so the findings do not support the 'Blood-Type' diet hypothesis.

Publication types

• Research Support, Non-U.S. Gov't
• ABO Blood-Group System / genetics*
• Cardiovascular Diseases / etiology*
• Cardiovascular Diseases / metabolism
• Cross-Sectional Studies
• Patient Compliance
• Risk Factors
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• ABO Blood-Group System

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What Is the Blood Type Diet?

Rachel MacPherson is a health writer, certified personal trainer, certified strength and conditioning specialist, and exercise nutrition coach based in Halifax.

Elena Klimenko, MD, is a board-certified doctor in internal medicine and is licensed in medical acupuncture and homeopathy.

Verywell / Debbie Burkhoff

What You Can Eat

What you cannot eat.

• How to Prepare & Tips
• Is It a Healthy Choice for You?

At Verywell, we believe there is no one-size-fits-all approach to a healthy lifestyle . Successful eating plans need to be individualized and take the whole person into consideration. Prior to starting a new diet plan, consult with your healthcare provider or a registered dietitian, especially if you have an underlying health condition.

The blood type diet is based on the theory that your blood type determines the foods you should consume (and the exercise you should do) to achieve optimal health. The diet plan was originally developed by Peter D'Adamo, a naturopathic physician.

The idea behind the diet is that eating foods with lectins (a type of protein) incompatible with a person's blood type can cause blood cell clumping, called agglutination, and result in health problems such as heart or kidney disease or cancer. However, there is a lack of scientific evidence to support these claims.

What Experts Say

"Basing a diet on your blood type is not evidence-based and restricts many healthy foods. Nutrition experts do not support or recommend this diet for achieving nutrition or health goals."

— Kelly Plowe, MS, RD

The blood type diet emphasizes certain foods and exercise plans for different blood types. Regardless of blood type, the diet emphasizes eating whole foods and minimizing the intake of processed foods . 

According to D'Adamo, people with type A blood are predisposed to heart disease, cancer, and diabetes, and do better on an organic, vegetarian diet with calming, centering exercise, such as yoga and tai chi.

People with blood type A, who D'Adamo calls "cultivators," should follow a dairy-free, primarily vegetarian diet with a high intake of fruits, vegetables, grains, beans, legumes , nuts and seeds .

People with type B blood, according to D’Adamo, have a robust immune system and a tolerant digestive system, and are more adaptable than other blood types. However, people with type B are more susceptible to autoimmune disorders, such as chronic fatigue, lupus, and multiple sclerosis.

D'Adamo recommends moderate physical exercise and balance exercises , along with a "well-rounded" diet, for people with blood type B, or "nomads." People in this group should eat a highly varied diet including fruits and vegetables , grains, beans, legumes, meat, poultry, fish, eggs, and dairy, but avoid nuts and seeds.

People with type AB blood are more biologically complex than other types, according to D’Adamo. Based on this belief, these people supposedly do best with a combination of the exercises and diets for types A and B, though meat should be limited.

It is believed that this blood type tends to have lower rates of allergies, but heart disease, cancer, and anemia are common. 

People with blood type AB, who D'Adamo calls "enigmas," can consume any food recommended for blood types A and B, although aiming for a mainly vegan diet is advised for this type.

Based on the blood type diet theory, people with type O blood do best with intense physical exercise and animal proteins, while dairy products and grains may cause problems.

According to D’Adamo, gluten, lentils, kidney beans, corn, and cabbage can lead to weight gain in people with this blood type. Health conditions associated with type O include asthma, hay fever, and other allergies, and arthritis.

People with blood type O, who D'Adamo calls "hunters," should stick to a dairy-free and grain-free diet high in meat and with a moderate amount of vegetables, eggs, nuts, and seeds.

In addition to specific foods, D'Adamo recommends and sells different supplements for each blood type. There is a specially formulated multivitamin, multimineral, lectin blocker, and probiotic/prebiotic blend for each blood type.

No foods are completely forbidden on the blood type diet. However, not all foods are considered beneficial for different blood types, and processed foods are discouraged for everyone.

How to Prepare the Blood Type Diet & Tips

There is no specific timing for meals or fasting periods required on the blood type diet. However, the plan advises against drinking water or other beverages with meals because it will dilute the natural digestive enzymes and make it more difficult to digest foods.

Pros of the Blood Type Diet

Like all fad diets, the blood type diet has positives and negatives.

• Encourages exercise : The blood type diet encourages exercise. Research shows that regular exercise combined with a healthy diet can lead to weight loss and promote weight management. However, there is no research to support the blood type diet as an effective weight-loss strategy.
• Emphasizes whole foods : Each blood type plan emphasizes choosing whole foods over processed foods, which is a healthy choice. The program also offers a wide variety of compliant foods for some of the blood types, which may make it easier to stick with.
• Can be a well-rounded choice : Although each blood type comes with its own set of dietary restrictions, the program is not a low-calorie diet with unhealthy restrictions on calorie intake. Plans for types B and AB are more well-rounded and can provide most if not all of the necessary nutrients for a well-balanced diet. However, the plans for types A and O restrict certain healthy food groups, which is not a smart long-term eating plan for many people.

Proponents of the blood type diet claim that the program can help you burn fat more efficiently, increase your energy levels, support your immune system , and lower your risk of major health problems like heart disease and cancer. However, there is currently a lack of scientific evidence to support these claims.

Cons of the Blood Type Diet

Despite some potential benefits, the blood type diet is not recommended by health experts and has several drawbacks.

• Not effective : There is no research to support that the blood-type diet is an effective weight-loss strategy.
• Not based on science : Eating for your specific blood type is not rooted in science. The available research on the blood type diet includes a study published in the journal PLoS One in 2014. Anyone following some of the diets, no matter their blood type, may either see benefits or no changes, according to the study.
• Requires unsubstantiated supplements : Although proponents of the blood type diet suggest that the use of dietary supplements can help people following the diet plan meet their nutritional needs, such supplements are not regarded as a reasonable substitute for a healthy, balanced meal plan.
• Can be restrictive : Since the diets prescribed for blood types A and O are restrictive, there's some concern that individuals following these diets may fail to achieve sufficient intake of many vitamins and minerals that are essential for health.
• Not backed by evidence : A research review published in 2013 no evidence to support any of the health claims associated with the blood type diet. In this review, scientists looked at 16 previously published reports on the blood type diet. Another 2020 review also found that there are no cardiometabolic benefits to be gained from the blood type diet.

Since any health changes occurred independently of the participants' blood types, the study's authors concluded that their findings do not back up the overall theory behind the blood type diet.

Is the Blood Type Diet a Healthy Choice for You?

The blood type diet is based on theory; it isn't rooted in scientific fact and its effectiveness has not been proven in clinical settings. The overall plan does emphasize whole, natural, and unprocessed foods, however, which makes it healthier than some pre-packaged meal plans or meal-replacement plans.

The U.S. Department of Agriculture's 2020–2025 Dietary Guidelines for Americans provide recommendations for a balanced diet. The following nutrient-dense foods are considered part of a healthy diet:

• Vegetables of all types and dark, leafy greens (e.g., kale , spinach , broccoli , Swiss chard , green beans ) 
• Fruits, especially whole fruits (e.g., apples, berries, melon)
• Grains, especially whole grains (e.g., quinoa , brown rice, oats )
• Lean animal protein (e.g., chicken breast, fish, turkey breast, eggs)
• Beans and legumes (e.g., beans, lentils, peas)
• Nuts and seeds (e.g., walnuts , almonds , sunflower seeds )
• Dairy products (e.g., reduced-fat milk, cheese, yogurt, as well as fortified soy-based dairy-free alternatives)
• Oils, including oils found in foods (e.g., olive oil, avocado oil , nuts, seafood) 

Depending on your blood type, this plan may or may not meet the USDA's definition of a healthy meal plan.

• The Type AB diet is the least restrictive and allows for the widest variety of foods to ensure adequate nutrition.
• The Type A diet prohibits meat and dairy, which have nutrients, namely protein, that can be found in other foods with careful planning.
• The Type B diet also offers a varied diet, with the exception of nuts and seeds, and meets most of the requirements of the USDA healthy eating plan.
• The Type O diet avoids dairy and grains, which are considered important parts of a healthy diet, according to the USDA. With careful planning, however, the nutrients found in grains and dairy can be made up by eating a variety of vegetables.

The blood-type diet does not suggest tracking or limiting calories. The USDA recommends a reduction of 500 calories per day for weight loss. On a 2,000-calorie diet, that's around 1,500 calories per day—but this number varies based on age, sex, weight, and activity level. Use this calculator to determine the right number of calories for you.

The prescribed plans for each blood type in the blood type diet eliminate some foods that are considered crucial to good health. Depending on your blood type, the diet may or may not adhere to federal dietary guidelines and is therefore not a recommended eating plan for overall health or weight management.

A Word From Verywell

While the blood type diet may offer some benefits in certain cases, following a health regimen that combines sensible calorie restriction and regular exercise is generally considered the most effective strategy for weight loss. If you're considering this diet plan, whether for weight loss or overall health, be sure to talk with a doctor or registered dietitian first.

Remember, following a long-term or short-term diet may not be necessary for you and many diets out there simply don’t work, especially long-term. While we do not endorse fad diet trends or unsustainable weight loss methods, we present the facts so you can make an informed decision that works best for your nutritional needs, genetic blueprint, budget, and goals.

If your goal is weight loss, remember that losing weight isn’t necessarily the same as being your healthiest self, and there are many other ways to pursue health. Exercise, sleep, and other lifestyle factors also play a major role in your overall health. The best diet is always the one that is balanced and fits your lifestyle.

Cusack L, De Buck E, Compernolle V, Vandekerckhove P. Blood type diets lack supporting evidence: A systematic review . Am J Clin Nutr . 2013;98(1):99-104. doi:10.3945/ajcn.113.058693

Fock KM, Khoo J. Diet and exercise in management of obesity and overweight .  J Gastroenterol Hepatol . 2013;28 Suppl 4:59-63. doi:10.1111/jgh.12407

Koliaki C, Spinos T, Spinou Μ, Brinia Μ-E, Mitsopoulou D, Katsilambros N. Defining the optimal dietary approach for safe, effective and sustainable weight loss in overweight and obese adults .  Healthcare (Basel) . 2018;6(3). doi:10.3390/healthcare6030073

Wang J, García-Bailo B, Nielsen DE, El-Sohemy A. ABO genotype, 'blood-type' diet and cardiometabolic risk factors . PLoS ONE . 2014;9(1):e84749. doi:10.1371/journal.pone.0084749

Barnard ND, Rembert E, Freeman A, Bradshaw M, Holubkov R, Kahleova H. Blood type is not associated with changes in cardiometabolic outcomes in response to a plant-based dietary intervention . Journal of the Academy of Nutrition and Dietetics. 2021;121(6):1080-1086. doi:10.1016/j.jand.2020.08.079

U.S. Department of Health and Human Services and U.S. Department of Agriculture.  2020–2025 Dietary Guidelines for Americans. Ninth Edition .

U.S. Department of Agriculture. I want to lose a pound of weight. How many calories do I need to burn? .

By Rachel MacPherson, BA, CPT Rachel MacPherson is a health writer, certified personal trainer, and exercise nutrition coach based in Halifax.

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December 4, 2020

New study debunks blood type diet

by Physicians Committee for Responsible Medicine

A study published in the Journal of the Academy of Nutrition and Dietetics by researchers with the Physicians Committee for Responsible Medicine—a nonprofit of 12,000 doctors—debunks the 'blood type diet' by finding that blood type was not associated with the effects of a plant-based diet on body weight, body fat, plasma lipid concentrations, or glycemic control.

This new study is based on a randomized control trial whose main findings were published in JAMA Network Open on Nov. 30. That trial randomly assigned overweight participants with no history of diabetes to an intervention or control group on a 1:1 ratio for 16 weeks. Participants in the intervention group followed a low-fat, plant-based diet. The control group made no diet changes. The key finding is that a plant-based diet ramps up metabolism as measured by an increase in after-meal calorie burn of 18.7%, on average, for the intervention group over the control.

To consider a potential connection between blood type and diet, researchers took the additional step of conducting a secondary analysis among intervention-group participants of the 16-week randomized clinical trial. They considered whether the effects of a plant-based dietary intervention on body weight , blood lipids , and glycemic control are associated with ABO blood type. The 'blood type diet' recommends a mainly plant-based diet for those with blood type A, while it recommends a diet heavy in meat for people with blood type O.

"We found that blood type made no difference," says study author Neal Barnard, MD, president of the Physicians Committee. "While the blood type diet says that a plant-based diet should be better for blood type A and less so for blood type O, it turned out to be beneficial for people of all blood types, and there was no evidence that meaty diets are good for anyone.

"Our research shows that all blood types benefit equally from a vegan diet based on the consumption of fruits and vegetables, legumes and whole grains, looking specifically at weight loss and cardiometabolic health in overweight adults," he says.

Main outcomes that were measured were body weight, fat mass, visceral fat volume, blood lipids, fasting plasma glucose, and HbA1c. T-tests compared participants with blood type A to all other participants (non-A), and individuals with blood type O to all other participants (non-O).

There were no significant differences in any outcome between individuals of blood type A and non-A, or between individuals of blood type O and non-O. Mean body weight change was -5.7 kg for blood type A participants and -7.0 kg for non-A participants, and was -7.1 kg for type O participants and -6.2 kg for non-O participants. Mean total cholesterol decreased 17.2 mg/dl in the type A group and 18.3 mg/dl for non-A participants, and decreased 17.4 mg/dl among type O participants and 18.4 mg/dl for non-O participants.

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The Blood Type Diet: Science or Fiction?

If you have been interested in nutrition for some time, you will likely have come across the blood type diet. The idea behind it is that those with certain blood types gain better health outcomes on specific diets; it was popularized in 1996 by Dr. Peter D’Adamo’s bestselling book, Eat Right 4 Your Type . While there are more subgroups, there are four main blood types that he focuses on in the book, categorized as follows: [1]

Type A: This is the more plant-based blood type, known as the agrarian. People with type A blood should eat a diet centered on plants and free of red meat, which is thought to be toxic to them.

Type B: Known as the nomad, these people should avoid chicken, pork, wheat, corn, lentils, and tomatoes, but eat most other plants and meats, as well as some dairy products.

Type AB: This blood type is a mix between types A and B and is known as the enigma. They may eat seafood, soy, dairy, beans (except kidney beans), and grains (except corn), while avoiding beef and chicken.

Type O: These are known as the hunters who are meant to eat a high-protein, high-meat diet, similar to a modern paleo diet. They also eat fish and certain fruits and vegetables; however, they should steer clear of dairy, grains, and legumes.

If you are questioning the validity of this theory after reading the previous descriptions, you are not alone. To assess the idea, I will explore the history and science behind the blood type diet theory.

Protein Consumption & Blood Type

One of the claims underlying this theory is that certain proteins in food cause agglutination, or clumping, of blood cells depending on blood type. [1] Lectins are proteins found in the plant kingdom, concentrated in legumes, and a select few types of lectins have been found to cause reactions with certain blood types. For example, in a petri dish, lectins from raw lima beans are seen reacting with type A blood. [2] The majority of lectins, however, react with all blood types, throwing a wrench into this theory. [3] Furthermore, lectins are only found in significant amounts in raw legumes. It only requires a minimal amount of cooking to destroy the lectins, casting further doubt on this theory. [4]

One of the more humorous claims made by Dr. D’Adamo in support of the blood type diet is that those with type O are to follow a caveman diet since type O is the oldest of the blood types. Even if this were true, that would hardly suffice as a solid reason for adopting a specific eating pattern; however, it is not true. Type O is actually the newest blood type! [5] The fact that type O is the simplest of the blood types does not mean it is the oldest, as Dr. D’Adamo claims. In addition to these claims, it is also said that those with type O produce more stomach acid than other blood types. While one study did find that there was slightly more stomach acid in those with blood type O, it was not to any significant degree that would suggest they should eat more high-protein foods. [6] Even if that were the case, they would also gain the ability to digest higher amounts of legumes, meaning their diet wouldn’t need to focus on meat.

Missing Research

As you can imagine, Dr. D’Adamo was under a fair bit of scrutiny from the scientific community with the release of his first book, but he had answers for the skeptics. He told critics that he was currently in year 8 of a 10-year study on blood type diets and reproductive cancers with the promise of great results. [1] However, the world has been waiting since 1998 for that study to be released. When he released his book, Arthritis: Fight it with the Blood Type Diet , he made more promises of upcoming research. [7] This time, he said he was conducting a 12-week, randomized, controlled trial on blood type diets and rheumatoid arthritis, again promising great results. That alleged study never saw the light of day either, causing me to suspect that the results of these studies did not show what their author wanted, or that they were never conducted in the first place.

Since Dr. D’Adamo didn’t seem to be producing his own research, independent researchers decided to take it upon themselves to evaluate the diet. A 2013 systematic review that sifted through 1,415 studies determined that there is not even one credible study establishing the benefits of a blood type diet! [8] In 2014, a study that evaluated nearly 1,500 people found that regardless of blood type, following a type A diet (predominantly plant-based diet) was associated with better overall cardiometabolic health. [9]

Norwegian researchers took particular interest in the blood type diet theory since Eat Right 4 Your Type sold 40,000 copies in Norway. Researchers concluded that any dietary shift away from a standard American diet is likely to produce positive health outcomes; however, many of the claims made by the book should be “considered junk and without scientific foundation.” [10] [11] Some even go so far as to call it “crass fraud.” [10] That may seem harsh, but under Norway’s Quack Act, it would be illegal to even promote the blood type diet there! [11]

After reviewing the literature, or lack of literature, it is quite clear that there is no scientific validation for the blood type diet. At best, it can award some benefit through the elimination of many processed foods that are prevalent in a standard American diet, but there are certainly better options out there. [10] We have mountains of evidence supporting a plant-based diet for the majority of the human species, including research that was designed to specifically evaluate the effects of the blood type diet. [9] I believe Dr. Hans Diehl, director of the CHIP program, sums up the scientific legitimacy of Eat Right 4 Your Type perfectly when he says, “Years ago when this book came out, I thought I might write a book called: Eat Right For Your Shoe Size. ”

• D’Adamo, P. & Whitney, C. Eat Right 4 Your Type. G.P. Putnam’s Sons, New York, 1996.
• Sharon, N. & Lis, H. History of lectins: from hemagglutinins to biological recognition molecules. Glycobiology. 2004;14(11):53R-62R.
• Nachbar, M.S. & Oppenheim, J.D. Lectins in the United States diet: a survey of lectins in commonly consumed foods and a review of the literature. Am J Clin Nutr. 1980;33(11):2338-45.
• Thompson, L.U. et al. Effect of Heat Processing on Hemagglutinin Activity in Red Kidney Beans. Journal of Food Science. 1983;48(1):235-236.
• Damian, M. Is it true that in earlier times humans were all O blood type (in ABO blood group) and that A, B and AB blood type occurred later by mutation of the O blood type gene? Evolution. 2010.
• Sievers, M.L. Hereditary aspects of gastric secretory function: Race and ABO blood groups in relationship to acid and pepsin production. The American Journal of Medicine. 1959;27(2):246-255.
• D’Adamo, P. Arthritis: Fight It with the Blood Type Diet. G.P. Putnam’s Sons, New York, 2004.
• Cusack, L. et al. Blood type diets lacking supporting evidence: a systematic review. The American Journal of Clinical Nutrition. 2013;98(1):99-104.
• Wang, J. ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors. PLoS ONE. 2014;9(1):e84749.
• Melter, H.M. et al. Blodtypedietten – visjonaer vitenskap eller tull? Tidsskrift for Den norselegeforening. 2002;14(122):1402-5.
• Moen, T. Blood Type Diet – Science or Fantasy? Tidsskrift for Den Norske legeforening. 2011;3(121):355-8.

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by Peter D'Adamo There are thousands of digestive enzyme supplements out there and available to the general public. However, just like the process of optimizing one’s food selection, the typical digestive enzyme formulas lean too heavily on the one-size-fits-all mantra.

Variations between the blood types regarding the production and array of digestive enzymes have been extensively reported in the medical literature. That’s why I thought it was important to develop a line of enzymes that took the strengths and weaknesses of each blood type into account.

After over two years of development and testing, we’re ready to release these new TypeZyme formulas.

The Integrative Healthcare Symposium awarded Peter D’Adamo, ND, as the recipient of its 2023 Leadership Award, which was presented to him today during the Integrative Healthcare Symposium in New York City.

The Leadership Award recognizes a pioneer whose contributions have shaped integrative healthcare and paved the way for other practitioners and professionals. This year, David Brady, ND, DC, CCN, DACDN, IFMCP, FACN, chief medical officer for Diagnostic Solutions Labs, presented the honor.

Notable past recipients include Andrew Weil, MD, David Perlmutter MD, FACN, ABIHM, Joe Pizzorno, ND, Mark Hyman, MD, and Tieraona Low Dog, MD.

Some observational data shows that high fructose intake is associated with metabolic syndrome, obesity, and liver disease. Observational studies are ones where the researchers observe the effect of a risk factor, diagnostic test, or treatment without trying to change who is or isn’t exposed to it.

One study found that consuming 255 grams of fructose per day did lead to an increase in liver fat and reduced insulin sensitivity. It also showed the same result if you consumed 255 grams of straight glucose as well, suggesting it may not be just the fructose that is the issue.

Your blood type has everything to do with how you digest your food, your ability to respond to stress, your mental state, the efficiency of your metabolism, and the strength of your immune system. “Blood types are critical predictive markers for disease,” says Dr. Peter D’Adamo. And in light of the current coronavirus pandemic, this significance is even more profound.

Is there a link between blood type and susceptibility to COVID-19 – the disease caused by the novel coronavirus SARS-CoV-2? Recent research points to the answer being “yes.” In fact, several studies indicate that those with Blood Type A may be more vulnerable to contracting the disease, and those with Blood Type O may possess protective genes that put them at lower risk.

The statements made on our websites have not been evaluated by the FDA (U.S. Food & Drug Administration). Our products and services are not intended to diagnose, cure or prevent any disease. If a condition persists, please contact your physician. Copyright © 2015-2020, Hoop-A-Joop, LLC, Inc. All Rights Reserved.      Log In

Embracing complexity: making sense of diet, nutrition, obesity and type 2 diabetes

• Open access
• Published: 14 February 2023
• Volume 66 , pages 786–799, ( 2023 )

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Nutrition therapy has been emphasised for decades for people with type 2 diabetes, and the vital importance of diet and nutrition is now also recognised for type 2 diabetes prevention. However, the complexity of diet and mixed messages on what is unhealthy, healthy or optimal have led to confusion among people with diabetes and their physicians as well as the general public. What should people eat for the prevention, management and remission of type 2 diabetes? Recently, progress has been made in research evidence that has advanced our understanding in several areas of past uncertainty. This article examines some of these issues, focusing on the role of diet in weight management and in the prevention and management of type 2 diabetes. It considers nutritional strategies including low-energy, low-fat and low-carbohydrate diets, discusses inter-relationships between nutrients, foods and dietary patterns, and examines aspects of quantity and quality together with new developments, challenges and future directions.

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Diet, nutrition and type 2 diabetes: what is the evidence?

Diabetes is a metabolic disorder with the potential for multiple adverse health consequences. It is also a public health challenge, with a rising global burden. Estimates indicate that there were approximately 537 million people worldwide with diabetes in 2021, which is projected to rise to 783 million by 2045, with type 2 diabetes constituting the majority (>90%) of this burden [ 1 ]. Diet and nutrition are of indisputable significance in reducing this burden because the development of type 2 diabetes is characterised by obesity and insulin resistance, leading to hyperglycaemia, and both weight and glycaemic control are directly related to food consumption.

Diet and nutrition are thus central as modifiable factors in both the management and the prevention of type 2 diabetes. This is supported by three lines of evidence. First, when adhered to, medical nutrition therapy in those with type 2 diabetes can match or exceed the glycaemic control that can be achieved by glucose-lowering medication in the short term, and can be useful in maintaining control [ 2 ]. Second, the proof of principle was established in the early 2000s that, among people with non-diabetic hyperglycaemia, the onset of type 2 diabetes can be delayed or prevented, with as much as a 58% relative risk reduction, through a supported intensive lifestyle intervention including dietary changes and physical activity [ 3 ]. The real-world impact of lifestyle modification strategies has been demonstrated [ 4 ], outside the highly controlled conditions of clinical trials, and such a strategy has been found to be effective in the UK National Health Service (NHS) [ 5 ]. Third, it has been demonstrated that remission of type 2 diabetes can be achieved through dietary means [ 6 ], resulting in a major shift in scientific understanding of the pathophysiology of type 2 diabetes, from a condition previously thought to be progressive and irreversible to one that can be brought under control to normal functioning.

However, defining the optimal diet for type 2 diabetes is a challenge and dietary strategies used in research have varied between different studies. This is largely because diet is intensely complex, with multiple components and influences on food consumption (Fig. 1 ). Concomitantly, interest in diet, nutrition and health is intense, with a deluge of scientific publications, matched equally by popular media coverage that is saturated with nutrition over-claims and ‘miracle diets’. This is also a field where vested interests are rife [ 7 ]. A search on PubMed (25 November 2022) using the terms ‘diet OR nutrition OR food OR nutrient OR dietary pattern OR diet quality’ and ‘type 2 diabetes OR non-insulin dependent diabetes’ yielded 52,833 hits, with over 3000 articles published each year since 2014; repeating the search using the term ‘obesity’ yielded 165,617 hits. What evidence should we trust?

Complexity of diets and multiple influences affecting food intakes. HEI, Healthy Eating Index. Influencing factors (boxes) adapted with permission from Afshin et al [ 83 ] © 2014 John Wiley & Sons. This figure is available as a downloadable slide .

The hierarchy of evidence framework and quality assessment tools have been applied to sift through the vast amount of evidence. Several reviews of the research evidence have been carried out [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ], enabling the incorporation of the best available evidence in dietary guidelines issued by authoritative agencies, including but not limited to the ADA [ 15 ] and Diabetes UK [ 16 ].

In a nutshell, this evidence highlights some key dietary principles. Healthy weight maintenance is critical to both prevent and manage type 2 diabetes; a pattern of food intake that mitigates type 2 diabetes risk includes the habitual consumption of vegetables, fruits, legumes, whole grains and cereal fibre, dairy products such as yoghurt, and nuts, and several overall dietary patterns are effective. In contrast, type 2 diabetes risk is elevated with a pattern of habitual dietary intake that includes processed and unprocessed red meat, refined grains and sugar-sweetened beverages. This evidence provides support that some foods should be emphasised and promoted while the consumption of others should be reduced or avoided, rather than the adage about everything in moderation.

This article does not cover the wide range of topics already discussed in existing reviews and guidelines. It focuses instead on selected hot topics that have been the subject of debate and on new developments in understanding in the field.

Weight management at the core, but how?

Body weight with increased adiposity is mechanistically linked to both the development and the progression of type 2 diabetes, typified by resistance to insulin action (insulin resistance) and an inadequate compensatory insulin secretory response by pancreatic beta cells. The relationship between adiposity, insulin resistance and beta cell function varies between individuals but the benefits of weight loss apply across the different pathophysiologies [ 17 ]. Weight loss is related to improved glycaemic control: the greater the weight loss, the greater the improvement in HbA 1c . A weight loss goal of 5–7% of initial body weight for people with overweight or obesity is recommended for clinical benefit, while weight loss of 15% can be disease modifying with the possibility of remission of type 2 diabetes [ 2 , 18 ].

Of the three options for weight management, bariatric surgery and pharmacotherapy are effective, but dietary strategies offer population-wide benefits without medicalisation. However, the weight loss and weight management diet market is vast and is projected to increase from US$192.2 billion in 2019 to US$295.3 billion by 2027. This promotion of a vast range of dietary products and strategies can be bewildering. An important question is therefore which dietary strategies are effective?

Remission of type 2 diabetes through diet-related weight loss

The proof of principle of the potential for reversibility or remission of type 2 diabetes with weight loss came first from the field of bariatric surgery [ 19 , 20 ]. However, surgery is not suitable for, or acceptable to, all people with type 2 diabetes. Surgery also has the potential for complications, side effects and challenges. One such challenge is the large prevalence of type 2 diabetes, which renders surgery an unrealistic option at the scale required, even if it were financially possible. There is high interest, therefore, in dietary means to achieve diabetes remission.

The nutritional basis for the remission of type 2 diabetes used in the UK-based Diabetes Remission Clinical Trial (DiRECT) was centred on major caloric restriction and weight loss with an associated reduction in hepatic fat and hepatic glucose output and improved beta cell function [ 6 ]. Among people with type 2 diabetes in primary care who were randomised to either a diet very low in energy (very low calorie diet) or usual care, mean body weight fell by 10 kg in the intervention group and 46% remained free of diabetes (i.e. in remission; HbA 1c <48 mmol/mol [<6.5%]) at 1 year and off all glucose-lowering and antihypertensive medications [ 21 ]. The intervention comprised total diet replacement (3452–3569 kJ/day [825–853 kcal/day] liquid formula diet for 12–20 weeks), stepped food reintroduction (2–8 weeks) and then structured support for weight loss maintenance. The greater the weight loss, the greater the likelihood of remission (86% at 1 year for weight loss ≥15kg; 57%, 34% and 7% for weight loss of 10–15 kg, 5–10 kg and <5 kg respectively). In addition, the effects were durable, with 36% of people in sustained remission at 2 years [ 22 ]. Further research is needed to understand the longer term effects of remission on the complications of type 2 diabetes, but current results support the remission of type 2 diabetes as a practical target in primary care.

In an endorsement of this approach, the UK NHS has rolled out a 12 week intervention consisting of a low-energy meal replacement diet for people with type 2 diabetes and a BMI >27 kg/m 2 (or >25 kg/m 2 if from a minority ethnic group in whom risk occurs at a lower BMI) ( https://www.england.nhs.uk/2022/01/nhs-soups-and-shakes-diet-helps-thousands-shed-the-pounds/ ). The goal is to recruit 5000 people from general practice; over 2000 people have already participated, showing the feasibility of this approach.

A focus on nutrients for weight and glycaemic control

Traditionally, dietary guidance has focused on macronutrient composition. Most dietary guidelines recommend intakes of <30–35% of energy from total fat, 45–55% of energy from carbohydrates and the remainder, ~15–20% of energy, from protein, both in the general population and in those with type 2 diabetes. For weight management, low-fat diets were favoured based on the higher energy density of fat, at 38kJ/g (9 kcal/g), compared with that of carbohydrate or protein, at 17kJ/g (4 kcal/g). More recently, low-carbohydrate diets have gained popularity. The optimal macronutrient composition is hotly debated.

Low-fat or low-carbohydrate diets for weight management?

The Look-AHEAD: Action for Health in Diabetes (Look-AHEAD) trial compared an intensive lifestyle intervention with a control condition of support and education in people with type 2 diabetes. The weight loss strategy, comprising energy reduction (5021–7531 kJ/day [1200–1800 kcal/day]) through a low-fat diet, was effective. Greater weight loss was achieved in the intervention group at 1 year, with a net difference in weight of –7.9% (95% CI –8.3% to –7.6%); at year 4, the net difference in weight was –3.9% (95% CI –4.4% to –3.5%) [ 23 ]. Similar low-fat diet approaches have been used in other trials of the primary prevention of type 2 diabetes [ 3 ]. In contrast, in the energy-deficit diet in the type 2 diabetes remission trial (DiRECT), the proportions of macronutrients were inconsequential, with >50% of energy coming from carbohydrates [ 22 ]. A recent umbrella review of the evidence concluded that weight management in type 2 diabetes using hypocaloric diets does not depend on any particular macronutrient profile [ 24 ].

More broadly, among adults with overweight or obesity in the population without consideration of type 2 diabetes, individual studies show differing results favouring one nutrient or another but, when the totality of the evidence is appraised, both low-fat and low-carbohydrate diets of varying protein content are effective for weight loss [ 25 ]. The challenge lies in adherence to the prescribed diets. A systematic review of the effects of low-fat and low-carbohydrate diets on weight loss in RCTs of at least 1 year’s duration and with a similar intervention intensity across groups found that low-fat diets were efficacious compared with usual intake [ 26 ]. But, when low-fat diets were compared with low-carbohydrate diets, there was greater weight loss in the low-carbohydrate diet group. However, the magnitude of the difference in weight loss between low-carbohydrate and low-fat diets was modest at only 1.15 kg, which is statistically significant but may have little clinical meaning. As a limitation, caloric restriction was a component of many of the weight loss interventions included, but not all; for example, some included studies gave dietary advice to eat a low-carbohydrate diet ad libitum [ 26 ]. Future research should seek to address design limitations; however, current research indicates that small effects on weight loss from one macronutrient type or another are unlikely to be of clinical significance. A key challenge is weight maintenance and prevention of weight regain, which is typical following weight loss.

Although overall dietary carbohydrate or fat content has been extensively studied in relation to weight loss and maintenance, protein intake has been less so. Higher protein intake after weight loss has been shown to result in significantly lower weight regain, related to increased satiety and energy efficiency [ 27 ]. For early weight loss maintenance over 6 months, an RCT tested different combinations of protein consumption and glycaemic index (GI) compared with a control diet among those who had lost at least 8% (equivalent to 11 kg) of their initial weight on a 3347 kJ/day (800 kcal/day) diet [ 28 ]. Consuming a low-protein/high GI diet led to subsequent weight regain (mean of 1.7 kg [95% CI 0.5 to 2.9]), while a modest increase in protein content and a modest reduction in GI led to improvements (reductions) in the degree of weight regain over 6 months. Evidence for long-term weight loss maintenance is generally sparse. Observational prospective data from the National Weight Loss Registry indicated that weight loss maintenance over 10 years was related to low-fat-based energy restraint combined with physical activity [ 29 ]. Further research is needed to better understand the dietary strategies and other factors important in weight loss maintenance.

Low-carbohydrate diets for glycaemic control in type 2 diabetes

For glycaemic control in type 2 diabetes, studies from clinical practice or from digital or commercial programmes have promoted low-carbohydrate diets based on significant benefits for HbA 1c , of a mean decrease of 11 mmol/mol (1% unit decrease), together with reductions in glucose-lowering medication use [ 30 , 31 ]. Interpretive challenges include the presence of bias owing to the lack of randomisation, self-selection into groups and unbalanced sample sizes or intensities of interventions in the study arms and lack of a comparator group. However, a number of systematic reviews and meta-analyses of RCTs are available that reduce such limitations [ 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ].

Evidence from RCTs indicates that lower carbohydrate diets have benefits over higher carbohydrate diets in the short term up to 6 months, but these are not maintained over time [ 34 , 36 ]. In the UK, the Scientific Advisory Committee on Nutrition appraised the available evidence, including 48 individual RCTs from eight systematic reviews. It concluded that lower carbohydrate diets were effective for glycaemic control in type 2 diabetes compared with higher carbohydrate diets, with a greater reduction in HbA 1c (weighted mean difference –4.7 mmol/mol [–0.47%]) in the short term (3–6 months), but this benefit was not maintained at 12 months [ 39 ].

Despite extensive research on low-carbohydrate diets, there are several challenges that limit firm conclusions. First, definitions of what a ‘low-carbohydrate diet’ is range from moderate carbohydrate restriction to very-low-carbohydrate or ketogenic diets (see Text box ‘Definitions of carbohydrate-focused diets’). Across RCTs, prescribed carbohydrate intakes in the lower carbohydrate groups ranged widely, from 14% to 50% of energy intake, and reported carbohydrate intakes were moderate at 26–45% of energy intake in the majority of the primary RCTs [ 39 ]. Second, in the case of isoenergetic diets (maintaining the same overall energy intake), a low-carbohydrate diet is by default higher in fat and vice versa. As many individual studies did not specify isoenergetic study arms, it is difficult to tease out whether the glycaemic change was influenced by differential changes in weight as a result of differing energy intakes. Third, because of differences in or a lack of information in study protocols on adjustment of glucose-lowering medication, it is hard to infer whether criteria for remission of type 2 diabetes were met [ 40 ].

Low-carbohydrate diets seem to be generally safe and well tolerated in the short term; concerns in the longer term relate to the potential atherogenic lipid profile [ 38 , 41 ] or micronutrient deficiency [ 42 ] or their use in people with chronic kidney disease or pregnant women, in whom there is a need for further evaluation. Accumulating evidence from prospective studies with long-term follow-up data indicates that both high and low intakes of carbohydrates may have adverse health impacts on mortality risk, with a U-shaped relationship [ 43 ]. However, such research has been carried out in general populations and needs to be replicated, and further research is needed in those with type 2 diabetes. In the meantime, the ADA dietary guidelines for people with diabetes were updated in 2019, making it explicit that low-carbohydrate diets can be endorsed (see Text box ‘Definitions of carbohydrate-focused diets’).

Nutrition and pathways to obesity and type 2 diabetes

The above focus on energy and macronutrients is rooted in two contesting mechanistic explanations that link dietary intake to obesity and type 2 diabetes. In the energy balance model, energy matters because the law of thermodynamics dictates that when energy intake exceeds energy expenditure weight gain occurs. The link between obesity and the development of type 2 diabetes is strong and, with caloric deficit-induced weight loss, remission of type 2 diabetes is possible. In these scenarios, a calorie is a calorie and excess calories result in adipose tissue accumulation and weight gain.

In contrast, the ‘carbohydrate–insulin model’ proposes that obesity is a cause, not the consequence, of excess caloric intake [ 44 ]. Here, the dysregulation of fat storage and metabolism is the central defect, driven by high-carbohydrate diets that produce spikes of hyperinsulinaemia that promote glucose uptake into tissues, suppress release of fatty acids from adipose tissue and stimulate fat and glycogen storage. Thus, less energy remains available for use by the rest of the body, driving hunger and overeating. In this scenario, not all calories are equal. It has been proposed that energy from refined carbohydrates promote a disturbed hormonal milieu linked with increased hunger, a slower metabolic rate and reduced energy expenditure, leading to adiposity.

The debate between these mechanistic processes continues [ 45 , 46 , 47 ]. However, it is increasingly clear that a focus on energy intake does not account for the impact that diet quality has on long-term weight gain and type 2 diabetes through diverse physiological processes. These include diet-induced thermogenesis, brain reward, appetite, hunger, satiety, digestion, the release and action of hormones, for example insulin, hepatic de novo lipogenesis, interactions with the gut microbiome and energy expenditure [ 48 ]. Moreover, a focus on considering a single macronutrient type has limitations that can lead to unhelpful reductionist messages to avoid a macronutrient without reference to its quality and food sources.

Beyond a focus on nutrient quantity: the relevance of nutrient type, quality and food sources

RCTs of macronutrient manipulation have focused exclusively on quantity. This ignores the fact that health effects will vary substantially by nutrient type or quality. For dietary fats, a vast literature exists on the importance of distinguishing between saturated, polyunsaturated, monounsaturated and trans fats. Health effects also vary by carbohydrate type (starch, sugar or fibre), degree of processing (whole grain vs refined grain), glycaemic response after consumption (GI and load) and food structure (solid or liquid form).

There is substantial evidence from meta-analyses for inverse (beneficial) associations between the consumption of fibre [ 49 ], particularly cereal fibre [ 50 ] and wholegrains [ 11 ], and the incidence of type 2 diabetes. However, evidence is more mixed for the dietary GI, which reflects the differential blood glucose-raising potential of foods with similar carbohydrate content, and a related measure, the glycaemic load (GL), which accounts for the amount of available carbohydrate. For example, the meta-analysis by Reynolds et al found inverse associations between fibre intake and several disease endpoints, including type 2 diabetes and mortality, but associations with GI and GL were non-significant [ 49 ]. Mixed and inconclusive results were also reported in reviews of a link between GI, GL and HbA 1c or fasting glucose [ 15 ]. The OmniCarb RCT compared four diets with varying GI and carbohydrate content in overweight or obese individuals with hypertension or pre-hypertension. This was a crossover feeding study with each diet based on a Dietary Approaches to Stop Hypertension (DASH)-type diet pattern [ 51 ]. Compared with a high GI (65% on the glucose scale), high-carbohydrate (58% energy) diet, a low GI (40% on the glucose scale), low-carbohydrate (40% energy) diet did not significantly improve insulin sensitivity, lipid levels or blood pressure. This type of evidence indicates that GI values have a low utility, but further research contradicts this. Other reviews with a more nuanced approach have reported a positive association between GI or GL and type 2 diabetes [ 52 ]. Similarly, some reviews and individual large cohorts have also reported a positive (adverse) association of high GI or GL with CHD or CVD [ 53 ], as well as a likely benefit of low GI or GL dietary patterns for glycaemic control and cardiometabolic risk factors in people with type 1 diabetes or type 2 diabetes [ 54 ]. A take-home message is that multiple aspects of carbohydrate quality are relevant and should be considered where possible because intakes of fibre, wholegrain and the GI and GL values of foods are likely to be highly correlated and may have confounding effects if not accounted for in diet–disease associations.

A point to note is that, when consumption of one nutrient type is manipulated (to eat less or more of it), this impacts the consumption of other nutrient types—the so-called ‘nutrient substitution’, in which one nutrient substitutes for another within isoenergetic consumption. Moreover, there are both ‘healthy’ and ‘unhealthy’ low-fat or low-carbohydrate diets.

The Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) RCT tested diet quality, comparing ‘healthy’ low-carbohydrate and low-fat regimens [ 55 ]. Both diet groups were instructed to maximise their non-starchy vegetable intake, minimise added sugars, refined flours and trans fats and focus on whole foods. Both diet types were effective, with a mean weight loss of 5.3 kg and 6 kg for the healthy low-fat and healthy low-carbohydrate diets, respectively, at 12 months, but there was no significant between-group difference [ 55 ]. In both diet groups there were also improvements at 12 months in secondary outcomes, including fasting glucose and insulin levels, body fat percentage, waist circumference, blood pressure and lipid profiles, except for LDL-cholesterol level, which was reduced in the low-fat group but increased in the low-carbohydrate group.

A crossover trial compared different levels of carbohydrate restriction and food sources in people with prediabetes or type 2 diabetes over two 12 week periods. Carbohydrates comprised <20% of energy in the very-low-carbohydrate ketogenic diet and <40% in the low-carbohydrate Mediterranean-style diet [ 56 ]. Both diets incorporated non-starchy vegetables and avoided added sugars and refined grains; the ketogenic diet avoided legumes, most fruits (except a few berries in small amounts) and whole grains whereas the Mediterranean-style diet incorporated these foods. Both diets resulted in improvements that were not significantly different. Specifically, mean HbA 1c levels decreased by 9% and 7% in the ketogenic and Mediterranean-style diet groups, respectively, and weight decreased by 8% and 7%, respectively. The ketogenic diet group achieved greater improvements in triglyceride and HDL-cholesterol levels than the Mediterranean-style diet group but had higher LDL-cholesterol levels (percentage change +10% vs –5%, respectively). The diets were ad libitum but participants in both groups reported consuming on average 1046–1255 kJ/day (250–300 kcal/day) less compared with baseline. The ketogenic diet group had a lower fibre intake and consumed lower levels of micronutrients (folate, vitamin C and magnesium). This study was of short duration and longer term research is needed, but its findings do not justify achieving a low-carbohydrate status by avoiding fruits, legumes and whole grains, which are considered part of a healthy diet in other longstanding research.

In sum, the consideration of nutrients in isolation has led to unhelpful polarised debates on whether low-fat or low-carbohydrate diets are superior. Macronutrients are not homogeneous entities: individual nutrients are derived from foods and people eat food in overall dietary patterns.

Beyond nutrients: foods and dietary patterns

Foods are complex mixtures of thousands of components—the food matrix—that have different physicochemical properties and health effects. This is illustrated by the opposite directions of association with the incidence of CHD seen for different foods rich in saturated fats. Consumption of dairy products such as yoghurt and cheese is inversely related to CHD incidence whereas consumption of red and processed meat is positively associated with CHD incidence [ 57 ]. This was corroborated by research showing that people who ate more saturated fats from red meat and butter were more likely to develop CHD than those who ate more saturated fats from cheese, yoghurt and fish [ 58 ]. This highlights the need to consider food sources together with the macronutrients they contain rather than the nutrients in isolation.

A consensus on dietary factors for the prevention of type 2 diabetes has been established from the comprehensive evidence base and incorporated into dietary guidelines. Broadly this suggests the benefits of the consumption of fruit, vegetables, nuts, seeds, wholegrains and yoghurt and the potential harms associated with sugar-sweetened beverages and red and processed meat. For some foods, such as fruit juice, artificially sweetened beverages, lean and fatty fish, milk and eggs, uncertainty remains with regard to their benefits for type 2 diabetes prevention [ 14 ].

Highly processed or ultra-processed foods of both plant and animal origin are increasingly consumed globally and have been related to a number of adverse health impacts. They include foods that have undergone industrial processing and that contain added ingredients such as salt, sugar, fat and artificial preservatives, stabilisers or colours, prolonging shelf life and reducing cost. An RCT compared the ad libitum consumption of ultra-processed foods with consumption of unprocessed foods. A total of 20 participants received all meals, matched for energy and macronutrient content, in a controlled setting for 28 days [ 59 ]. Ultra-processed food consumption led to substantially greater energy intake (+2090 kJ/day [+500 kcal/day] on average over 14 days) and weight gain (+0.9 kg over 14 days vs weight loss of equal magnitude during the 14 days of the unprocessed diet phase). Longer term prospective studies have provided evidence for an association of ultra-processed food consumption with the development of type 2 diabetes [ 60 ].

A number of food-based dietary patterns have a place in the prevention of type 2 diabetes based on observational evidence, including the Mediterranean, DASH and plant-based diets, but only the Mediterranean diet has been investigated in an RCT, both for the prevention and for the management of type 2 diabetes [ 61 ]. For many named popular diets such as the paleo, Atkins, Ornish and Zone diets, there is RCT evidence for short-term weight management but without any meaningful differences between them [ 25 ], while no evidence for their role in the prevention of type 2 diabetes is available.

For dietary patterns, quality matters too. For instance, plant-based diets are generally considered healthy, but not all such diets are alike. In one study, plant-based diets that were high in refined carbohydrates or were ultra-processed were associated positively with the incidence of type 2 diabetes [ 62 ].

Embracing complexity: key messages

Diet is a complex risk exposure.

Diet is non-binary, unlike, for example, tobacco, for which zero is best. Diet is multidimensional and hierarchical in nature. Foods belong within food groups and may be consumed unprocessed (e.g. beef or pork) or processed (e.g. ham or bacon). Foods contain nutrients (e.g. meat fat or protein as macronutrients; haem iron as a micronutrient) or additives and preservatives if processed, and are part of overall dietary patterns (e.g. the Mediterranean diet with relatively low intakes of red meat or a low-carbohydrate diet regimen with relatively high intakes of meat).

The continuum of dietary exposures should be considered, as well as ‘food substitution effects’, because when more or less of one food type is consumed it impacts the consumption of other foods as part of the overall energy intake.

Diet is hard to measure

Tools such as food frequency questionnaires or 24 h dietary recall instruments are commonly used to assess habitual dietary intakes. Despite efforts towards validating these tools and their ability to produce credible estimates of diet–disease associations, critics have called for them to be abandoned, considering them flawed because of their reliance on memory and cognition and issues of bias and measurement error [ 63 , 64 ]. Suggestions for suitable alternatives are sparse, however. Emerging digital technologies—smartphone apps, cameras for food imaging and wearable devices—hold promise but are not yet of ‘research grade’, with demonstrable validity and reliability [ 65 ]. They are also not free from measurement error, nor gaming, consciously or subconsciously. A promising complementary approach is the use of objective biomarkers of dietary intakes, for instance plasma vitamin C and carotenoids as markers for fruit and vegetable intake, or plasma omega-3 fatty acids as a marker for seafood consumption [ 66 ]. However, these too have sources of random and systematic errors as well as interpretive challenges, that is, the extent to which circulating levels reflect intake compared with metabolism.

No method is perfect, but the use of validated dietary instruments with repeat measures can approximate habitual diet. Moreover, there are benefits in using a combination of methods to harness their complementary strengths and deal with relative weaknesses.

The study design of nutritional research is challenging

The RCT design is considered the gold standard in the hierarchy of evidence-based medicine framework, but for complex behavioural exposures such as diet, unlike for pharmaceuticals, RCTs are more challenging. The bulk of the evidence base for nutrition and health has come from long-term observational prospective cohort studies. Both observational and interventional studies have relative strengths and weaknesses. Observational studies are typically limited by confounding and bias but when rigorously conducted they can yield reliable and valid results, from which causal inference can be made [ 14 ]. Dietary RCTs have several challenges. They have a specific set of limitations including a lack of blinding, lack of an appropriate control group, issues with feasibility and cost and challenges of adherence and attrition. The inability to pinpoint the specific nutritional component(s) is another challenge, such as in some of the above-cited RCTs, which could not separate out the effects of macronutrient type and energy intake. Moreover, dietary trials can vary greatly in quality, and consistency of findings and comparability are limited by the populations and endpoints included, for example healthy or diseased participants, free-living or tightly controlled conditions, and a variety of intermediate endpoints or clinical outcomes. In practice, RCTs also suffer from poor methodology and unreliable findings, as evidenced by an appraisal of nearly 21,000 RCTs [ 67 ].

Causal inference is strengthened when there is consistent evidence from different study designs. Inferring causality from observational evidence is possible by applying the Bradford Hill criteria, and Mendelian randomisation is a tool that can be applied in some situations to evaluate causal relationships [ 68 ].

No design is perfect and the evolution of improvements in all study designs—RCTs and observational studies—must continue. New concepts are emerging, such as ‘ n -of-1’ trials and adaptive trial design, which need robust testing in the nutrition field. There is strong concordance in findings from prospective observational studies and RCTs and the two study designs should complement each other [ 7 ]. The best evidence base is that which evaluates all the relevant diverse types of evidence.

Uncertainty remains for some dietary factors

Consensus on the potential benefits and harms of many foods and dietary patterns has been established. However, for some dietary factors controversy remains, for example in the case of non-nutritive or artificial sweeteners such as aspartame, saccharin and sucralose. These sugar substitutes can help decrease daily energy and carbohydrate intakes but whether they are helpful for obesity and type 2 diabetes in the long term is debated [ 69 ]. The use of such sweeteners is predicted to rise in line with the public health policy on sugar reduction, which in the UK includes a soft drinks industry levy applied to soft drinks containing high amounts of added sugar; manufacturers have responded to this with reformulations using sugar substitutes. To resolve this uncertainty, future research will ideally use a combination of research designs including well-conducted short-term RCTs and long-term prospective studies and employ nutritional biomarkers of artificial sweeteners.

Noise and confusion are commonplace in the nutritional field

Everyone is interested in food. From news media to social media, books and blogs, information and misinformation on nutritional topics is everywhere. Conflicts of interest cannot always be avoided. Trusted resources are needed, including high-quality research evidence, improved dietary guidelines [ 70 ] and greater involvement of academic institutions and health agencies.

There are many influences on what we eat beyond individual lifestyle choice (Fig. 1 )

There is a gap between dietary advice and dietary intakes. Consider the public health message to eat five portions a day of fruit and vegetables. Despite strong health promotion efforts, ~12% of the population aged over 15 years in Europe meet this goal [ 71 ]. In a global context, compliance with eating five portions a day of fruit and vegetables is affected disproportionately by income, such that achieving this goal costs an estimated 52%, 18%, 16% and 2% of household income in low-, low- to middle-, middle- to upper- and high-income countries, respectively [ 72 ]. Further, sobering current examples of wider determinants of food choice include the effects of Brexit, the COVID-19 pandemic and the Russian invasion of Ukraine on availability, access and food security.

To improve and maintain dietary adherence, there is a need to operate both at the individual level and in the policy space across the entire food system (see Text box ‘Strategies to promote dietary adherence to healthy eating’). Education, dietary guidelines and strategies that enable people to make healthy food choices are necessary but not yet universally available.

Interest has recently risen in ‘food is medicine’ interventions in healthcare systems, such that a healthy diet can be prescribed in a manner equivalent to the prescription of medication, particularly for those with food insecurity. Such interventions include food prescriptions or the provision of medically tailored groceries or meals, which in those with diabetes can achieve improvements in diet quality and in HbA 1c of a comparable magnitude to those seen with glucose-lowering medication [ 73 ]. Pilot data in people with uncontrolled type 2 diabetes and food insecurity are impressive, with substantial reductions in HbA 1c in those enrolled to receive fresh food on prescription [ 74 ]. Similarly, a meta-analysis of healthy food prescription programmes reported that an increase in consumption of fruit and vegetables by a mean of 0.8 daily servings was associated with significant reductions in BMI and HbA 1c [ 75 ]. Although there were methodological limitations, these studies highlight the potential effectiveness of such dietary interventions and the case for investment in further research.

There are exciting new developments on the horizon

This is illustrated by two examples. First, greater understanding of the relationships between eating and circadian biology is emerging to shed light on so-called chrononutrition [ 76 ]. In addition to considerations of quantity and quality appraised above, chrononutrition considers the impact of the timing of food intake on metabolic health. As an example, the benefits of intermittent fasting and time-restricted feeding are becoming apparent for weight loss [ 77 ] and health more broadly [ 78 ], but research specifically targeted at type 2 diabetes is needed. Second, to improve on current dietary guidance, which is based on population averages, promising research on ‘precision nutrition’ aims to combine information from personal, biological, social and environmental factors to target individuals or population subgroups sharing similar characteristics [ 79 ]. Although still in its infancy, the use of technologies that enable information from genetics, metabolomics, proteomics and the gut microbiome to be integrated with clinical and biochemical data together with machine learning has the potential to enable the development of personalised nutrition interventions [ 80 ].

Conclusions

Diet and nutrition play a central role in both the prevention and the management of type 2 diabetes but the complexity of diet and some key controversies have posed challenges in the field. The latest research evidence has advanced our understanding of the importance of shifting away from the decades-long focus on the quantity of isolated nutrients to nutrient quality, nutrient food sources and overall dietary patterns. New advances in research hold promise for helping to resolve current ongoing uncertainties, and exciting future directions are anticipated (see Text box ‘Future directions: food for thought’).

Abbreviations

Dietary Approaches to Stop Hypertension

Glycaemic index

Glycaemic load

National Health Service

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Acknowledgements

I acknowledge D. Bhagtani’s help with Fig. 1 (MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine).

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NGF was a member of the Joint Scientific Advisory Committee on Nutrition/NHS England/Diabetes UK Working Group, which was initiated to review the evidence on lower carbohydrate diets compared with current government advice for adults with type 2 diabetes. The views expressed are her own and not those of the Group.

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The author was the sole contributor to this article.

NGF is supported by the Medical Research Council Epidemiology Unit (MC_UU_00006/3) and the NIHR Biomedical Research Centre Cambridge: Nutrition, Diet, and Lifestyle Research Theme (IS-BRC-1215-20014). She is an NIHR Senior Investigator. The views expressed are those of the author and not necessarily those of the NIHR or the Department of Health and Social Care.

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Forouhi, N.G. Embracing complexity: making sense of diet, nutrition, obesity and type 2 diabetes. Diabetologia 66 , 786–799 (2023). https://doi.org/10.1007/s00125-023-05873-z

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• Apr 1, 2024

Vegan Diet Reduces Insulin Requirements for Type 1 Diabetes

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A new study led by Physicians Committee Director of Clinical Research Hana Kahleova, MD, found that a low-fat vegan diet has a strikingly beneficial effect on type 1 diabetes. 1 Physicians Committee researchers had already established a low-fat vegan diet as the nutritional treatment of choice for type 2 diabetes, but its effect on type 1 diabetes had not previously been studied. In the 12-week trial, despite increased carbohydrate intake, participants on the vegan diet reduced their total daily insulin dose by 12.1 units/day and lost an average of 5.2 kilograms.  Although the primary problem in type 1 diabetes is the autoimmune destruction of the insulin-producing beta-cells of the pancreas, patients frequently also have insulin resistance, just as in type 2 diabetes. A low-fat vegan diet effectively counters insulin resistance, reducing insulin requirements, and improves body weight. 2

• Kahleova H, Znayenko-Miller T, Smith K, et al. Effect of a dietary intervention on insulin requirements and glycemic control in type 1 diabetes: a 12-week randomized clinical trial. Clin Diabetes . 2024:cd230086. doi:10.2337/cd23-0086
• Barnard ND, Cohen J, Jenkins DJ, et al. A low-fat vegan diet improves glycemic control and cardiovascular risk factors in a randomized clinical trial in individuals with type 2 diabetes. Diabetes Care . 2006;29(8):1777-1883. doi:10.2337/dc06-0606

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Is It Healthier to Eat Your Vegetables Before Your Carbs?

“Nutrient sequencing” is said to regulate blood sugar. We asked experts if the science holds up.

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By Nikki Campo

• April 2, 2024

Q: I’ve heard that it’s best for my health to eat a salad before dinner. But if I’m eating vegetables regardless, does the order really matter?

It’s a popular internet health hack: Eat foods in the “right” order — vegetables first, proteins and fats second, carbohydrates last — and you’ll significantly reduce your resulting spike in blood sugar, which can therefore reduce cravings, fatigue and health risks like Type 2 diabetes, proponents say.

Past research on the topic , sometimes referred to as nutrient or meal sequencing, has concluded that it can indeed benefit blood sugar, especially for those with Type 2 diabetes or pre-diabetes.

For everyone else, it’s not as cut-and-dried, said Dr. Alpana Shukla, a physician and researcher at Weill Cornell Medicine in New York City who has studied food order. Though there are some reasons to consider giving it a try, she said.

What does the research suggest?

Existing studies on the benefits of meal sequencing are small, but the results are consistent, experts say.

In one 2023 review of 11 studies , for instance, researchers concluded that people who saved carbohydrate-rich foods for the end of a meal, after vegetables and proteins, had significantly lower blood sugar levels than when they consumed them first.

In one 2019 study of 15 people with pre-diabetes, Dr. Shukla and her colleagues asked the participants to eat a meal of skinless grilled chicken, salad and ciabatta in three different orders on three different days: ciabatta first, followed 10 minutes later by the chicken and salad; chicken and salad first, followed by the ciabatta; and salad first, followed by the chicken and ciabatta.

Researchers measured participants’ blood sugar levels right before they ate, and every 30 minutes for three hours after each meal. They found that when the participants ate the chicken and salad before the bread, their blood sugar spikes following the meal were about 46 percent lower than when they ate the bread first.

Researchers aren’t entirely sure why this might be. One theory is that eating fats, fiber and proteins first delays stomach emptying , which could slow the absorption of sugars from the carbohydrates into the bloodstream, Dr. Shukla said.

Barbara Eichorst, vice president of health care programs at the American Diabetes Association, said it makes sense for people with Type 2 diabetes or pre-diabetes to consume vegetables and proteins first during meals, since, unlike carbohydrates, vegetables and proteins don’t rapidly turn into sugar and cause high blood glucose spikes.

For those who have Type 2 diabetes, some limited research even suggests that this blood sugar lowering effect could be comparable with certain diabetes medications, said Nicola Guess, a clinical dietitian and researcher at the University of Oxford in Britain. Though more research is needed on the topic.

Should everyone eat like this?

Research has also shown that eating carbohydrates last in a meal can reduce blood sugar spikes in people who don’t have diabetes . But the experts said that healthy people usually don’t need to micromanage their blood sugar in this way.

A properly functioning body will bring blood sugar levels back down to normal within hours after eating a meal, said Dr. Vijaya Surampudi, an endocrinologist at UCLA Health.

Nonetheless, since proteins, fats and fiber-rich vegetables take longer to digest than simple carbohydrates, saving carbs for last can help people feel fuller for longer, said Dr. Domenico Tricò, an assistant professor of internal medicine at the University of Pisa in Italy who studies food order.

Research also suggests that eating this way can stimulate the gut to produce more of a satiety hormone called glucagon-like peptide 1, or GLP-1. (The diabetes drug Ozempic is designed to mimic this hormone.)

“GLP-1 slows digestion and tells your brain you’re not hungry,” Dr. Surampudi said. But some experts said it’s not clear if the small increases in this hormone from meal sequencing alone (compared with the large increase you’d get from a drug like Ozempic) would make a big difference in how sated you feel.

If you tend to feel sluggish after meals, front-loading them with vegetables or protein could help, Dr. Shukla and Dr. Surampudi said.

Some research also suggests that saving carbohydrates for the end of a meal can make you more likely to fill up on vegetables and protein and eat fewer simple carbohydrates, which tend to have fewer nutrients and more calories, Dr. Shukla said.

The bottom line, the experts said, is that while meal sequencing is one of many healthy eating strategies, it’s not something to stress about. Dietary trends like these sometimes result in making people anxious, which can lead to disordered eating.

“If it’s easy for you, then you should go for it,” Dr. Tricò said. But if not, just aim for high-quality food you enjoy. Loading up on vegetables at every meal is more important than focusing too intently on the order of your food, Dr. Guess said.

Nikki Campo is a freelance writer in North Carolina.

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Bariatric surgery provides long-term blood glucose control, type 2 diabetes remission.

People with type 2 diabetes who underwent bariatric surgery achieved better long-term blood glucose control compared to people who received medical management plus lifestyle interventions, according to a new study supported by NIDDK . In this large, pooled follow-up study, participants who underwent bariatric surgery, also called metabolic or weight-loss surgery, were also more likely to stop needing diabetes medications and had higher rates of diabetes remission up to 12 years post-surgery compared to participants who received medical management and lifestyle intervention for their diabetes. Additional exploratory analyses showed that bariatric surgery had important, beneficial effects on HbA1c and weight loss among participants with a body mass index (BMI) between 27 and 34 (within overweight and lower obesity ranges), which lend important information about the benefit of surgery in people with type 2 diabetes who fall short of the traditional, higher BMI threshold of 35 for bariatric surgery. These results were published in JAMA in February.

Discovery of gene in mice could open new therapeutic avenues for a rare neurodegenerative disorder

A recent study led by NIDDK researchers sheds light on a rare neurological disease, GM1 gangliosidosis, which occurs when people lack an enzyme responsible for breaking down the lipid known as GM1 ganglioside. As a result, the lipid accumulates in the brain and causes severe neurological symptoms. The researchers discovered that in mice, a gene called Neu3 creates an alternative pathway to help degrade the lipid, which may explain why mice exhibit a much milder form of GM1 gangliosidosis compared to what people with the disease experience. When the researchers turned off the Neu3 gene in mice, the severity of the disease increased. Specifically, the mice experienced a faster onset of neurological symptoms, greater neurodegeneration, and shorter lifespan. The findings, which published in the Journal of Lipid Research in December, advance understanding of the potential mechanisms underlying the severity of GM1 gangliosidosis and could lead to new therapies to alter the course of the disease. In future studies, the research team will explore whether the Neu3 gene modifies other neurodegenerative diseases resulting from a build-up of gangliosides in the brain.

Switching to a vegan or ketogenic diet rapidly affects immune system

Researchers at the National Institutes of Health, including NIDDK, observed rapid and distinct immune system changes in a small study of people who switched to a vegan or a ketogenic (also called keto) diet. Scientists closely monitored various biological responses of people who ate either a vegan or keto diet for two weeks, then switched to the opposite diet for another two weeks. They found that the vegan diet prompted responses linked to innate immunity—the body’s non-specific first line of defense against pathogens—while the keto diet prompted responses associated with adaptive immunity—pathogen-specific immunity built through exposures in daily life and vaccination. Metabolic changes and shifts in the participants’ microbiomes—communities of bacteria living in the gut—were also observed. More research is needed to determine if these changes are beneficial or detrimental and what effect they could have on nutritional interventions for diseases such as cancer or inflammatory conditions. The paper was published in Nature Medicine in January.

NIDDK scientists develop standard models of human fat cells to help advance research

Human fat is a complex organ that plays a critical role in sustaining health, and the lack of standardized models of brown and white adipose tissue, or fat cells, have made it challenging to understand its structural, functional, and genetic characteristics. In a new study, NIDDK researchers tackled this challenge by characterizing human brown and white adipose tissue cells donated by a male patient during an abdominal surgery. In analyzing these cells, the researchers identified the physiological mechanisms that allow brown fat cells to generate heat in response to cold temperatures, thus demonstrating how standardized models of fat tissue can be used to better advance knowledge on a cellular level. Standardized models of human fat cells will also help researchers generate reproducible study results. Published in December in Endocrinology , and selected as the journal’s “featured article of the week” in January, the study lays the groundwork for future physiologic, pharmacologic, and genetic studies on human fat and its role in metabolic disease and health.

NIDDK researchers develop analytical method to identify genes associated with risk of Alzheimer’s disease

A new NIDDK study has identified nine genes potentially linked to higher risk of Alzheimer’s disease (AD) in people of African descent. The researchers developed a “gene-constrained” analysis, in which they counted and compared only moderate- and high-risk gene variants affecting gene function. This approach differs from the more common “genome-wide association study” (GWAS) method, which looks at all regions across the genome and is typically used when searching for genetic variants associated with complex diseases involving many genes, such as AD.

One of the genes the researchers identified was GNB5, which regulates G-protein signaling. The discovery of GNB5 as a risk gene for AD suggests that regulation of G-protein signaling may be critically involved in the development of the disease. In addition, the nine genes the researchers identified were not among previously identified genes linked to AD by the GWAS method. The results, which were published in The American Journal of Human Genetics in March, indicate that the gene-constrained approach might complement the GWAS method by enhancing the detection of genes associated with AD and other polygenic diseases.

Do sweeteners increase your appetite? New evidence from randomised controlled trial says no

Replacing sugar with artificial and natural sweeteners in foods does not make people hungrier -- and also helps to reduce blood sugar levels, a significant new study has found.

The double blind randomised controlled trial found that consuming food containing sweeteners produced a similar reduction in appetite sensations and appetite-related hormone responses as sugary foods -- and provides some benefits such as lowering blood sugar, which may be particularly important in people at risk of developing type 2 diabetes.

The use of sweeteners in place of sugar in foods can be controversial due to conflicting reports about their potential to increase appetite. Previous studies have been carried out but did not provide robust evidence.

However, the researchers say their study, which meets the gold standard level of proof in scientific investigation, provides very strong evidence that sweeteners and sweetness enhancers do not negatively impact appetite and are beneficial for reducing sugar intake.

The trial was led by the University of Leeds in collaboration with the The Rhône-Alpes Research Center for Human Nutrition. It is the latest study to be published by the SWEET consortium of 29 European research, consumer and industry partners which is working to develop and review evidence on long term benefits and potential risks involved in switching over to sweeteners and sweetness enhancers in the context of public health and safety, obesity, and sustainability. It was funded by Horizon Europe.

Lead author Catherine Gibbons, Associate Professor in the University of Leeds' School of Psychology, said: "Reducing sugar consumption has become a key public health target in the fight to reduce the rising burden of obesity-related metabolic diseases such as type 2 diabetes.

"Simply restricting sugar from foods without substitution may negatively impact its taste or increase sweet cravings, resulting in difficulties sticking to a low-sugar diet. Replacing sugars with sweeteners and sweetness enhancers in food products is one of the most widely used dietary and food manufacturing strategies to reduce sugar intake and improve the nutritional profile of commercial foods and beverages."

Principal investigator Graham Finlayson, Professor of Psychobiology in the University of Leeds' School of Psychology, said: "The use of sweeteners and sweetness enhancers has received a lot of negative attention, including high profile publications linking their consumption with impaired glycaemic response, toxicological damage to DNA and increased risk of heart attack and stroke. These reports contribute to the current befuddlement concerning the safety of sweeteners and sweetness enhancers among the general public and especially people at risk of metabolic diseases.

"Our study provides crucial evidence supporting the day-to-day use of sweeteners and sweetness enhancers for body weight and blood sugar control."

The study, which is the first of its kind, looked at the effects of consuming biscuits containing either sugar or two types of food sweetener: natural sugar substitute Stevia, or artificial sweetener Neotame on 53 adult men and women with overweight or obesity.

Until now, virtually all studies of the effects of sweeteners and sweetness enhancers on appetite and glycaemia have been conducted using beverages as the vehicle. Few studies include volunteers with overweight or obesity and few have included volunteers of both sexes.

Most studies have only compared a single sweetener, mostly aspartame, with a control, and very few studies have examined the effect of repeated daily intake of a known sweetener or sweetness enhancer in the normal diet.

The new trial took place at the University of Leeds and the Rhône-Alpes Research Center for Human Nutrition (CRNH-RA), France between 2021 and 2022. Participants were all aged 18 to 60, with overweight or obesity.

The trial consisted of three two-week consumption periods, where participants consumed biscuits with either fruit filling containing sugar; natural sugar substitute Stevia, or artificial sweetener Neotame, each separated by a break of 14-21 days. Day 1 and day 14 of the consumption periods took place in the lab.

Participants were instructed to arrive in the lab after an overnight fast, a blood sample was taken to establish baseline levels of glucose, insulin and appetite-related hormones. They were also asked to rate their appetite and food preferences.

After consuming the biscuits, they were asked to rate how full they felt over several hours. Glucose and insulin levels were measured, as were ghrelin, glucagon-like peptide 1 and pancreatic polypeptide -- hormones associated with the consumption of food.

The results from the two sweetener types showed no differences in appetite or endocrine responses compared to sugar, but insulin levels measured over two hours after eating were reduced, as were blood sugar levels.

SWEET project joint co-ordinator Professor Anne Raben, from the University of Copenhagen, Denmark, said: "The findings show that sweeteners are a helpful tool to reduce intake of added sugar without leading to a compensatory increase in appetite or energy intake, thereby supporting the usefulness of sweeteners for appetite, energy and weight management."

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Journal Reference :

• Catherine Gibbons, Kristine Beaulieu, Eva Almiron-Roig, Santiago Navas-Carretero, J. Alfredo Martínez, Beverley O’Hara, Dominic O’Connor, Julie-Anne Nazare, Alain Le Bail, Cécile Rannou, Charlotte Hardman, Moon Wilton, Louise Kjølbæk, Corey Scott, Hariklia Moshoyiannis, Anne Raben, Joanne A. Harrold, Jason C.G. Halford, Graham Finlayson. Acute and two-week effects of neotame, stevia rebaudioside M and sucrose-sweetened biscuits on postprandial appetite and endocrine response in adults with overweight/obesity—a randomised crossover trial from the SWEET consortium . eBioMedicine , 2024; 105005 DOI: 10.1016/j.ebiom.2024.105005

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