The Blood Type Diet?

The ‘blood-type’ diet is based on a popular book published in 1996, which has since sold over 7 million copies.^2,3 The idea is that our blood group reveals something about our ancestral dietary habits, and matching our current eating to those habits help reduce disease risk.

Those with blood group O, the hunter, are advised to eat a high-animal protein diet, blood type A, the agrarian, a mostly vegetarian diet, type B, the nomad, should eat a diet with lots of dairy, and blood group AB, the enigma, should eat somewhere between the type A and type B diets.

While a 2013 review¹ finding no scientific evidence to support the proposed benefits of the blood-type diet should have diminished much of the hype, internet articles providing advice for the diet keep showing up.

So, what do we believe?

Well, we now have two, well-done studies that can help us understand. The first looked at a cross-section of 1,455 healthy adults,⁴ while the second study followed 973 overweight adults for 6-months.³ Eating any of the blood-type diets was associated with favorable results. 

Here’s the catch.

In both studies, when the diet was matched to their specific blood types, there was no association with those favorable effects. In other words, when people ate any of the blood-type diet plans, they were generally prudent diets recommending a high consumption of fruit and vegetables and avoidance of processed foods. So, a type B blood type could eat the Type O diet and see improvement, the type AB could eat the Type A diet and see an improvement, and so on.

This might be a case of misattribution, where people are attributing their results to eating to their specific blood type. But, based on this data, they could have chosen any of the four diets, no matter their blood type. However, it should be noted that the type A or agrarian, mostly vegetarian diet, was consistently better than the others.

So, I will call this one ‘clarify,’ because the diet might actually work for a lot of people who are currently eating unhealthfully, but it appears to be because all four are prudent diets high in fruits and vegetables, and not because it has anything to do with matching to one’s blood type.

So, at least for now, it appears that the blood-type diet is just another way to stir one’s blood.

References

1. Cusack, L., De Buck, E., Compernolle, V., & Vandekerckhove, P. (2013). Blood type diets lack supporting evidence: A systematic review. The American Journal of Clinical Nutrition, 98(1), 99-104.
2. D’Adamo P., & Whitney C. (1996) Eat right 4 your type: the individualized diet solution to staying healthy, living longer and achieving your ideal weight. New York: Putnam; 1996.
3. Wang, J., Jamnik, J., García-Bailo, B., Nielsen, D. E., Jenkins, D. J., & El-Sohemy, A. (2018). ABO genotype does not modify the association between the “blood-type” diet and biomarkers of cardiometabolic disease in overweight adults. The Journal of Nutrition, 148(4), 518-525.
4. Wang, J., García-Bailo, B., Nielsen, D. E., & El-Sohemy, A. (2014). ABO genotype,‘blood-type’diet and cardiometabolic risk factors. PloS one, 9(1), e84749.