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Eating for your blood group — the theory, the foods, and the evidence
The Blood Type Diet, popularised by naturopath Peter D'Adamo in his book Eat Right 4 Your Type, claims that your ABO blood group — A, B, AB or O — should determine what you eat. According to the theory, each blood type evolved at a different point in human history and is therefore best suited to different foods. Eating the "wrong" foods for your type is said to cause weight gain and illness via compounds called lectins.
It's an appealing idea because it feels personalised — a diet tailored to your biology. However, it's important to be clear up front: there is no scientific evidence that blood type should determine your diet. Multiple studies have tested the theory and found no support for it. We include this guide so you can understand the claims and make an informed decision.
Favour
High-protein: meat, fish, vegetables. Said to do well on an almost Paleo-style diet.
Avoid
Grains, beans, legumes and dairy.
Favour
Mostly plant-based: vegetables, tofu, legumes, whole grains. Close to a vegetarian diet.
Avoid
Meat and most dairy.
Favour
A varied, balanced diet: meat (not chicken), dairy, grains and vegetables.
Avoid
Corn, wheat, lentils, tomatoes and chicken.
Favour
A mix of type A and type B recommendations: tofu, seafood, dairy and green vegetables.
Avoid
Caffeine, alcohol and cured meats.
The theory proposes that lectins — proteins found in many foods — react differently with each blood type, causing inflammation, digestive problems and weight gain when "incompatible" foods are eaten. While lectins are real and some are worth cooking thoroughly (raw kidney beans, for example), there is no evidence that they interact with blood type in the way the diet claims.
The Blood Type Diet has been directly tested. A 2013 systematic review in the American Journal of Clinical Nutrition found no studies supporting its claimed health effects. A 2014 study in PLOS ONE looked at over 1,400 people and found that while some blood-type diets did improve health markers, the improvements had nothing to do with the participants' actual blood type — they came from eating a healthier diet overall.
In other words: if a type A person eats the "type A" plant-rich diet and feels better, it's because they're eating more vegetables and fewer processed foods — not because of their blood group. A type O person would benefit from the same vegetables.
If following a blood-type plan helps you eat more whole foods and fewer processed ones, you may feel better — but the benefit is the healthier eating, not the blood-type matching. You can get the same result, with more flexibility, from a balanced approach like the Mediterranean diet or simply building a balanced plate. There's no need to restrict foods based on your blood group.
The Blood Type Diet, popularised by Peter D'Adamo, claims that your ABO blood group (A, B, AB or O) should determine what you eat. Each type is given specific foods to favour and avoid. The theory is that foods react with your blood type via compounds called lectins. There is no scientific evidence supporting this idea.
No. A large 2014 study published in PLOS ONE found that any health benefits people experienced were unrelated to their blood type — they came from following a generally healthier diet. A systematic review found no evidence to support blood-type-based eating. The theory is not accepted by the scientific community.
Each blood-type plan cuts out processed foods and emphasises whole foods, which improves most people's diets regardless of blood type. The benefit comes from eating more healthily overall, not from matching food to blood group. You would get the same benefit from any sensible whole-food diet.
The main risk is unnecessary restriction. Some versions tell certain blood types to avoid whole food groups (like grains or dairy) with no valid reason, which can make eating harder and risk nutrient gaps. It is not inherently dangerous, but it is built on an unproven theory.