Does blood type affect what type of food is best for you?

Question

I remember that, a few years ago, my parents were told that different blood types need to eat differently. From a quick look online, it seems to be called "Eat Right For Your Type."

It claimed that, depending on what your blood type is, some food groups should be preferred or avoided. For example, type O should prioritize meat and avoid wheat products; type A should prioritize vegetables and avoid meat. For a summary of the whole thing, see this article.

Is there any validity to those claims?

Answer 1

Your ABO blood type tells you which antigens of the ABO blood group are present on your red blood cells. The function of the A and B antigens are not known, but they are not essential, individuals without those antigens are healthy¹.

The ABO blood type has an effect on blood clotting¹, but there is no reliable evidence that it has an effect on metabolism. This does not mean that such a mechanism is impossible, but the burden of proof lies with Dr. Peter D'Adamo to provide evidence for his claims.

I could not find any clinical trials that would support this claim on his website, there are some scientific papers listed there, but those are just reviews of the literature. The Mayo clinic agrees, that there is no evidence for this claim,

There's also a recent study in PLOS One examining the blood type diet directly, and it found that there is no basis for it. The diets themselves provide some benefit, but that benefit is entirely independent from the blood type of the person:

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.

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_{[1] Dean L., Blood Groups and Red Cell Antigens [Internet]., Bethesda (MD): National Center for Biotechnology Information (US) (2005).}