Blood type diet
A 2013 systematic review found no studies testing the health effects of blood-type diets. In three later studies of about 2,500 adults, some blood-type diet patterns were linked to lower weight or heart risk markers, but the links were the same whatever a person's blood type. No trial has assigned people to these diets, and no harms were sourced.
- Status
- A dietary pattern, not a regulated product. It comes from the diet book Eat Right 4 Your Type.
- Also called
- blood-type diet, Eat Right 4 Your Type, Eat Right for Your Type, ABO diet, blood group diet, type O diet, type A diet, type B diet, type AB diet
- Followed for
- weight loss, heart health, digestion, disease prevention
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help2
Reported risks0
No risks sourced yet.
What people follow it for, and what was found
Shown to help2
Weight and waist
Linked to lower BMI or waist with closer adherence to type A, B, AB or O diet patterns, regardless of a person's own blood type.
Compared with people in the lowest third of each blood-type diet score [2], [3]
The numbers and sources
- Effect
- Closer adherence to the type A diet was linked to lower BMI and waist circumference [2]. At baseline, higher type B and AB scores were linked to smaller waists (100.8 against 105.4 cm for type B). Over 6 months, rising type A and type B adherence went with larger drops in BMI and waist, and rising type O adherence with drops in both [3].
- Population
- 1,455 adults [2]; 973 adults with overweight, 758 women [3].
- Sources
- [2], [3]
- Caveats
- Observational analyses of diet scores, including within a diet trial [3]. The links did not depend on blood type [2][3].
Heart risk markers
Linked to lower blood pressure, cholesterol, triglycerides and insulin with type A and AB diet patterns, whatever a person's blood type.
Compared with people in the lowest third of each blood-type diet score [2], [3]
The numbers and sources
- Effect
- Adherence to the type A diet was linked to lower blood pressure, serum cholesterol, triglycerides, insulin and insulin resistance. The type AB diet showed the same links except for BMI and waist. The type O diet was linked to lower triglycerides, and the type B diet showed no links [2]. At baseline, the highest third of type A scores had lower diastolic blood pressure than the lowest (70.9 against 73.3 mm Hg) [3].
- Population
- 1,455 adults [2]; 973 adults with overweight [3].
- Sources
- [2], [3]
- Caveats
- Cross-sectional links, not trial results. The links did not depend on blood type [2].
Not shown to help1
Benefit matched to blood type
Limited evidence: in three studies, eating for one's own ABO blood type did not change any blood-type diet's links with weight, waist or heart risk markers.
Compared with no study located that compared a blood-type diet with a standard diet [1]; people in lower thirds of each blood-type diet score, and people whose ABO genotype did not match the diet [2], [3]; people of other blood types on the same low-fat vegan diet [4]
The numbers and sources
- Effect
- A systematic review screened 1,415 references and found no study of the health effects of ABO blood-type diets [1]. In 1,455 adults, matching each blood-type diet score to the person's genotyped blood group did not change the size of any link with cardiometabolic markers [2]. In 973 adults with overweight, matching did not change any link at baseline or after a 6-month diet intervention [3]. On a 16-week low-fat vegan diet, weight change was -5.7 kg in blood type A and -7.0 kg in other types (P = 0.09), and -7.1 kg in type O and -6.2 kg in others (P = 0.33). Cholesterol, body fat and glucose changes did not differ by blood type [4].
- Population
- Studies in any population grouped by blood type [1]; adults in the Toronto Nutrigenomics and Health study [2]; adults in the Toronto Healthy Diet Study, mean BMI 32.5 [3]; 68 adults with overweight in the vegan arm of a randomized trial [4].
- Sources
- [1], [2], [3], [4]
- Caveats
- None of these was a trial that assigned people to blood-type diets. Diet scores came from a 196-item food frequency questionnaire [2][3], and [4] was a secondary analysis.
Claimed, not studied in people1
Digestion
Not studied in people. The diet's idea that food lectins clash with blood types rests on lab work, which found lectins common in foods but no blood-type-specific clumping.
No study in people. This rests on lab studies, how it acts in the body.
The numbers and sources
- Effect
- A systematic review found no study of any health effect of blood-type diets, digestion included [1]. The diet proposes that lectins, sugar-binding proteins in some foods, cause clumping when they do not suit a person's ABO blood type [2]. In a lab survey, 29 of 88 common foods, including salad ingredients, fresh fruits, roasted nuts and processed cereals, showed lectin activity in agglutination tests [5]. The authors of a 2014 study, citing that survey, wrote that studies to date suggest no ABO-specific agglutination [2].
- Population
- Food extracts tested in the lab [5]. A systematic review [1] and the background of a study in 1,455 adults [2].
- Sources
- [1], [2], [5]
- Caveats
- Lectin activity in a test tube does not show what happens in the gut. No study measured digestive symptoms on a blood-type diet [1].
How trials defined it
No trial has assigned people to blood-type diets [1]. Studies scored how closely each person's diet matched each of the four blood-type diets using a 196-item food frequency questionnaire, and genotyped ABO blood group from two gene variants [2][3]. One analysis typed blood in people eating a low-fat vegan diet with weekly classes for 16 weeks [4].
Claims tested and not found
Sources
- Cusack L, De Buck E, Compernolle V, et al. Blood type diets lack supporting evidence: a systematic review. The American Journal of Clinical Nutrition. 2013. https://doi.org/10.3945/ajcn.113.058693
- Wang J, García-Bailo B, Nielsen DE, et al. ABO genotype, 'blood-type' diet and cardiometabolic risk factors. PLoS ONE. 2014. https://doi.org/10.1371/journal.pone.0084749
- Wang J, Jamnik J, García-Bailo B, et al. ABO Genotype Does Not Modify the Association between the "Blood-Type" Diet and Biomarkers of Cardiometabolic Disease in Overweight Adults. The Journal of Nutrition. 2018. https://doi.org/10.1093/jn/nxx074
- Barnard ND, Rembert E, Freeman A, et al. 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. https://doi.org/10.1016/j.jand.2020.08.079
- Nachbar MS, Oppenheim JD. Lectins in the United States diet: a survey of lectins in commonly consumed foods and a review of the literature. The American Journal of Clinical Nutrition. 1980. https://doi.org/10.1093/ajcn/33.11.2338