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Each individual should eat certain foods and avoid others depending on their blood type, according to naturopath Peter D'Adamo. But does his theory survive scientific scrutiny?

Do you remember the blood type diet? Naturopath Peter D'Adamo suggested a person's blood type should influence the foods he eats in his book Eat Right for Your Type in 1996. The blood type diet soon became a much-talked about fad in alternative circles, and it's still around today. 

What Is A Blood Type Diet?

What does D'Adamo say about the right diet for you? Well, type O is supposed to be the ancestral blood group — the one blood group all humans shared at one point. Back when all humans had type O blood, they were hunter-gatherers that largely relied on meat, so type O folks are advised to eat a diet high in animal protein. 

The theory says that type A came along later, when humans started farming. Hence, D'Adamo says, type A people thrive on a vegetarian diet. Type B is said to have originated during nomadic times, and a type B person who follows the blood type diet will eat a lot of dairy foods. Finally, D'Adamo says that type AB people have similar needs as type B individuals, but without fish and eggs. 

Eating the right diet for your blood type is supposed to help an individual achieve his or her optimal weight, as well as reduce the person's risk of chronic diseases. Each type is meant to avoid certain foods that "don't work well" with their blood, and eat the foods that are advised to reap the benefits. Additionally, specific types of exercise are recommended for each blood type.

And The Verdict Is...

It's certainly an fascinating theory. A Canadian research team from the University of Toronto agreed, and wanted to see if there was any scientific basis for the diet. They took a closer look at the eating habits of 1,455 healthy young adults, and looked at their blood types as well. 

"It was an intriguing hypothesis so we felt we should put it to the test," lead author Ahmed El-Sohemy says.

As part of that test, the study subjects completed a questionnaire about their food intake. The research team took blood samples from the subjects after they faster, and assessed cardiometabolic risk factors: insulin, cholesterol, and triglycerides.
They found that each blood group does indeed come with certain benefits:
  • Type O people have lower serum triglycerides
  • Type A people tend to have a lower BMI, lower blood pressure, lower triglyceride and insulin levels and a smaller waist
  • Type B people have better HDL cholesterol
  • Type AB people have lower blood pressure as well as lower serum total cholesterol, triglycerides and insulin levels

Do these findings indicate that the blood type diet works? No, not at all. When El-Sohemy and his colleagues compared the subjects' eating habits to the four individual blood type diets, some of the participants whose diet resembled D'Adamo's suggestions had favorable markers for heart health — in other words appropriate insulin, cholesterol, and triglyceride levels. This was not, however, found to correlate to the individuals' blood types.

What's El-Sohemy's conclusion? "The way an individual responds to any one of these diets has absolutely nothing to do with their blood type and has everything to do with their ability to stick to a sensible vegetarian or low-carbohydrate diet."


That's another dietary myth busted, then! The blood type diet was put to the test and — as El-Sohemy says — "we can now be confident in saying that the blood type diet hypothesis is false".

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