Through the years, I’ve frequently been asked does my blood type determine what diet would be best for me? Great question with varying responses depending on who you may ask. So, let’s dig a little deeper.

In 1996, Peter D’Adamo published a book titled, ‘Eat Right 4 Your Type’, about what is best to eat based on your blood type. He recommended a diet rich in fruits, vegetables, and grains for those with blood type A and a more meat-oriented diet for those with blood type O. One of the primary rationales for these recommendations was the idea that those with type A blood lacked the appropriate enzymes and adequate stomach acid needed to sufficiently break down animal protein.

You likely are aware, but just to be sure that we’re all on the same page, there are four major blood type groups determined by the presence or absence of two antigens, A and B, on the surface of red blood cells. Additionally, there is a protein called the Rh factor, which can be present (+) or absent (-). So, all in all, you can be one of eight blood types: A+, A-, B+, B-, AB+, AB-, O+, or O-.

For some context, note that the majority of people in the US have type O (45%) or type A (33%) blood. Those with type B blood comprise 18% of the population and AB genotypes are found in only 4% of the population. Hence, much of the discussion focuses on type O and A blood types. Note that these percentages differ among various ethnic backgrounds and race.

Is there a connection between different diseases and blood type? The Nurses’ Health Study and Health Professionals Follow-Up Study found that there was an 11% increased risk of heart disease in those with blood types other than O. The type O blood type has been associated with an increased risk of type 2 diabetes, compared to those with a B blood type.

In the Toronto Health Diet Study, men observed improvements in biomarkers following various diets, but ABO genotype did not modify this association. Following a six-month dietary intervention, individuals who adhered to the type A and type B diets reported significantly greater reductions in body mass index (BMI) and waist circumference, respectively. And those participants who followed the type O diet observed significant decreases in both BMI and waist circumference. So, essentially, despite whatever one’s ABO genotype was, adhering to a specific diet protocol resulted in health improvements.

Fast forward to 2021 and just last month, a study was published looking at the connection between blood type and diet. In this 16-week randomized controlled trial, researchers assessed the effects of a plant-based diet intervention on metabolic health outcomes. All participants were assigned to a vegan, low-fat diet - like D’Adamo had recommended for those with blood type A and advised against for those with an O blood type. This study reported no significant differences in cardiometabolic outcomes between blood type groups – body weight, body fat, plasma lipid concentrations, or glycemic control. Hence, consuming a plant-based diet offers protective benefits to those of all blood types, not just those with type A blood.

So, while we may continue to learn nuances of how our blood type impacts our nutrition and diet recommendations, based on the current research, your blood type does not determine the best diet for you. Furthermore, all of us can experience favorable health changes following a healthful diet.