Blood Type Diet

There are no shortage of diets publicized by celebrities and trusted medical professionals with bombastic promises of weight loss or improved health.

Many of these diets leech on peoples’ ingenuous nature for quick results and quest for healthier lives.

One example is the blood type diet which categorizes foods as beneficial, neutral, or avoid for each of the four blood types.

The Blood Type Diet

In 1996, Peter D’Adamo, a naturopathic practitioner, published Eat Right 4 Your Type, a best-selling book which popularized the blood-type diet.

In his book, he posited the idea that a diet based on blood type might have health benefits.

According to D’Adamo, each blood type has different abilities to process certain foods — including their inherent lectins.

Lectins are a type of sugar-binding proteins that serve numerous biological functions.

D’ Adamo claims that the different blood groups cannot properly metabolize certain lectins and by eating the wrong food, the lectin causes agglutination (cell clumping) somewhere in your body.

It’s this “dangerous glue” that causes everything from hormone imbalance to liver cirrhosis (scaring of the liver) and even hinder blood flow to the kidneys.

The Blood Types

D’Adamo formulated four separate profiles based on each of the blood types. In summary:

Type A

This blood type emerged with the rise in community living, when, thanks to the dwindling supply of game to hunt, human digestion was forced to adapt to carbohydrate consumption.

Type A’s, therefore, should eat a vegetarian diet, being mindful of their sensitive immune systems and natural inclination for stress. They should limit sugar and caffeine, and practice meditation.

Type B

Pushed from the savannas to the Himalayas, Type B’s developed in response to climactic changes. While types A and O are on the opposite side of the spectrum, B falls somewhere in the middle.

Corn, wheat, tomatoes, and peanuts cause weight gain while meats (except chicken), low-fat dairy, and green vegetables encourage weight loss. When they’re out of balance, the B’s develop stress and illness, but when they’re eating for their type, they are more physically fit than the other blood types.

Type AB

Type AB is the rarest and newest of the blood types. It emerged from the intermingling of A and B and, therefore, share both the benefits and challenges of each.

Seafood, dairy, green vegetables, and grains are on the menu, while caffeine, alcohol and smoked meats are shunned. They are intuitive, have low digestive enzymes, and should avoid highly competitive situations.

Type O

As the oldest blood type, Type O’s are well adapted for metabolizing animal protein and fat, but not grains or dairy.

Descending from hunters, the fight-or-flight response is strong in the O’s and can translate to increased aggression or manic episodes. They should avoid caffeine and alcohol, exercise regularly, and remember to chew slowly.

Evidence for the Blood Type Diet

D’Adamo’s supposition that people, based off their blood type, should eat different foods and exercise in a completely different manner is unsubstantiated.

And while there’s no evidence that blood type is tied with evolution, it’s likely that specific antigens evolved to protect us from diseases like malaria.

As such, there is a higher incidence for certain illnesses in different blood groups. The reasons, however, are unclear but probably have no connection with diet.

“There is currently no evidence that an adherence to blood type diets will provide health benefits, despite the substantial presence and perseverance of blood type diets within the health industry.” This is the take of review study published in the American Society for Nutrition.

The Takeaway

People may better their health while following one of these plans, not because they’re “eating right for their type,” but because they’re eating better than they were before.

One study, for example, found that following one of the blood type diets ( but not the B) was associated with improvements in certain biomarkers for cardiometabolic health.

The study, however, doesn’t show causality, as in the blood type diets caused these improvements in cardiometabolic health. In conducting the study, food frequency questionnaires were also used, which have their inherent pitfalls.

There are many unanswered questions between diet and health, but D’Adamo’s theory that all the answers are flowing in your veins is dubious.


Gavin Van De Walle, MS
Gavin Van De Walle, MS

Gavin Van De Walle, M.S. is the president of Supra Nutrition and a consultant for dietary supplement formulations. He is formally trained in human nutrition and bioenergetics.

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