by Lewis Chang, PhD
Based on the theory that each blood type (i.e., O, A, B, and AB type) represents distinct genetic traits and ancestral dietary habits, the popular “blood-type diet” advocates eating according to one’s blood type to achieve optimal health. For example, individuals who are type O (“the hunter”) would benefit most from a high-animal protein diet with avoidance of grains, legumes and dairy products; type A (“the agrarian”) are best with a vegetarian diet; type B (“the nomad”) are encouraged to eat dairy products while avoiding chicken, corn, wheat, lentils and tomatoes; and type AB (“the enigma”) should follow a dietary pattern between type A and B. However, the rationale and the proposed health claims of the blood-type diet have not been validated scientifically.
Researchers from the Department of Nutritional Sciences at the University of Toronto (Ontario, Canada) recently conducted a study to examine the validity of the blood-type diet.1 The study included 973 adults who participated in the Toronto Healthy Diet Study—a 6-month study that assessed the effect of dietary advice, food provision, or both on body weight and cardiovascular disease risk factors. Their mean age was 44.6 years and mean BMI was 32.5 kg/m2. A 196-item food-frequency questionnaire was used to assess the participant’s dietary intake at baseline and after 6 months. Then, the diet adherence scores were calculated to determine an individual’s relative adherence to each of the 4 blood-type diets.
The investigators found that following the blood-type diet was associated with improvements in cardiometabolic risk factors such as BMI and waist circumference. However, the beneficial effects were similar between those who matched the diet with the corresponding blood type and those who did not.1 For example, the type A diet was not only beneficial for type A individuals, but also equally beneficial for those with other blood types. This suggests that the benefit of a blood-type diet, which may simply represent a healthy eating pattern, is independent of a person’s blood type.
Although these results provide evidence against the blood-type-specific health claims made by advocates of the blood-type diet, the dietary patterns recommended by the blood-type diet are characterized by healthy, whole foods with avoidance of refined carbohydrates and processed products. Thus, those switching from the typical unhealthy Western diet to any blood-type diet likely will experience improvements in overall health. This may explain why many people have great confidence in this diet.
The study was supported by the Canadian Institutes of Health Research, and the results have been published in Journal of Nutrition.
Why is this Clinically Relevant?
- Individuals with higher adherence to the blood-type diet experienced improvements in cardiometabolic risk profile, but this effect was irrespective/independent of their blood type
- The health claims made by the blood-type diet remain unsupported by scientific evidence. However, the blood-type dietary pattern is rich in healthy foods and recommends avoidance of refined carbohydrates and processed foods
- Following recommendations from any of the blood-type diets will be an improvement from the typical, unhealthy Western diet. Therefore, those who follow the blood-type diet are likely to benefit from it.
- Wang J, Jamnik J, Garcia-Bailo B, Nielsen DE, Jenkins DJA, El-Sohemy A. ABO genotype does not modify the association between the “blood-type” diet and biomarkers of cardiometabolic disease in overweight adults. J Nutr. 2018;148(4):518-525.