January 20, 2023

The Blood Type Diet: Does It Really Work?

Research shows your blood type doesn’t matter when it comes to what you eat

Person holding up a bowl of fruit and a hamburger.

With so many diet options out there, wouldn’t it be nice to know if there was one that was really made for you?

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The blood type diet makes an appealing claim: Get personalized advice on the best way to eat based on your blood type.

This diet was developed in 1996 by Peter D’Adamo, ND, a naturopathic doctor. His book, Eat Right for Your Type, became a The New York Times bestseller.

But although people still follow the blood type diet today, there’s no scientific evidence to support the diet and experts have since criticized its concept, according to registered dietitian Devon Peart, RD, MHSc, BASc.

Peart shares what the blood type diet is about and why it’s flawed.

Why does eating for your blood type matter?

Peart explains that the basic idea of Dr. D’Adamo’s blood type diet is that your physiological response to food is linked to your blood type. As a result, he suggested you eat foods that were prevalent during the time your particular blood type evolved. According to Dr. D’Adamo, eating this way would increase your overall health and decrease your risk of chronic diseases.

The different types of blood

So, what does it mean when we say “during the time your particular blood type evolved”? Well, no one knows why we have different blood types, but popular theories suggest they developed over time. Blood types are based on what antigens (molecular structures) are on the surface of your red blood cells. The four major blood types are:

  • Type A contains the A antigen.
  • Type B has the B antigen.
  • Type AB has both A and B antigens.
  • Type O is the world’s most common blood type and has neither antigen.

What to eat for your blood type

Dr. D’Adamo assigned each blood type a particular way of eating based on when he believed that blood type was identified. He theorized that the foods you should eat are the ones that were most common in the human diet at that time.

The blood type diet was very specific about what foods are best for each blood type. For instance, it was recommended that people with blood type A load up on black beans, but stay away from kidney beans.

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Here’s a general overview of how Dr. D’Adamo saw each blood type’s diet:

Blood type O diet

According to Dr. D’Adamo’s research, “O” blood is the oldest type, hailing back to Cro-Magnon people, around 40,000 B.C. This was during the hunter-gatherer period. As a result, people with blood type O would eat a low-carb, high-protein diet.

Blood type A diet

Blood type A was the next to develop around 25,000 B.C., according to the diet. And this took place when people started farming. Dr. D’Adamo proposed that eating a plant-based diet was best for this blood type.

Blood type B diet

Blood type B developed in nomadic populations who focused on herding animals, around 15,000 B.C. Meat and dairy products dominated their diet, according to Dr. D’Adamo.

Blood type AB diet

A rare blood type, Dr. D’Adamo says AB developed fewer than 1,000 years ago. It’s a mix of blood types A and B and came about when the two populations — farmers and nomads — intermingled. Dr. D’Adamo’s diet recommendations included turkey, tofu, seafood and vegetables.

Problems with the blood type diet

You might see the problems with the blood type diet right away. It takes a lot of effort to follow the blood type diet because the lists of do’s and don’ts are so extensive for each group. And what about people living in the same household with different blood types? Would you be able to cook one dinner that would be healthy for your entire family?

Besides those practical challenges, Peart says the diet also has two major issues:

1. There’s a lack of evidence to support its claims

“Dr. D’Adamo looked at what humans were eating at the time the blood type potentially developed. He made the leap that their bodies were better adapted to that type of food. It’s a big leap — and there’s no evidence to support it,” says Peart.

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Plus, researchers debate the stages at which the various blood types emerged. For instance, a different theory holds that blood type AB was the original one (not blood type O) and that the three others mutated from it.

2. Research shows blood type doesn’t matter

Studies show that if you eat the diets recommended for blood types A, AB and O, you’ll get a positive outcome no matter your blood type, says Peart. For example, if you have type B blood, but follow the type A diet, which is a vegetarian diet, it’ll still lower your risk of heart disease.

“Research has shown that blood type doesn’t affect our response to foods,” she continues. “There’s no reason to choose a certain diet based on blood type. The positive results people get from this diet have to do with what they’re filling their plates with — more fruits and vegetables, good quality grains, and less and leaner meats.”

Should you try the blood type diet?

Like many other trendy diets (such as keto and pegan), the blood type diet has its fans and critics. If you want to try this diet and are blood type A, AB or O, there’s no harm in giving it a go. Those eating plans are healthy, no matter your blood type. But Peart doesn’t recommend the blood type B diet, which is higher in saturated fat, as that is linked to heart disease risk.

And following a proven anti-inflammatory diet, like the Mediterranean diet, can give you the same results with less headache. But the most important factor in finding the right diet? Choosing a healthy way of eating that best fits your life and that you can stick with for the long term.

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