Doesn't my blood type or ancestry mean I need meat?
Short answer: No. A systematic review found no evidence behind blood-type diets, and human nutritional needs don't vary by ancestry in a way that mandates meat.
Cusack et al., systematic review (2013)
The objection
“My blood type is O, the hunter type, so my body is built for meat. And my ancestors thrived on it, so it’s in my biology.”
The answer
It feels intuitive, and that’s exactly why it’s worth checking carefully rather than dismissing. The blood-type diet makes a testable claim: that people with type O, A, B or AB respond differently to foods. So it was tested.
A systematic review in the American Journal of Clinical Nutrition screened over 1,400 studies and found not a single one rigorously supporting the theory. A separate study of more than 1,400 people found that when blood-type diets did improve health markers, the benefit tracked the diet itself rather than the person’s blood group. Any “type O does better on this plan” result vanished once you accounted for whether people simply ate well. The hunter-gatherer story behind it is invented backstory, not evidence.
The ancestry version is shakier still. Human populations adapted to wildly different diets, from Arctic to tropical to agrarian, but those adaptations are about tolerances (lactase persistence, starch digestion) and not a requirement for meat. Our species’ core nutrient needs are universal: the same vitamins, minerals and amino acids, obtainable from plants plus B12.
One caveat sharpens the picture. Individuals genuinely do respond differently to diets, for reasons of genetics, gut microbiome and health status. That’s real personalised nutrition. But it has nothing to do with ABO blood groups, and it never points to “you, specifically, must eat animals.” The Academy of Nutrition and Dietetics confirms well-planned plant-based diets are adequate for everyone, every blood type included.