By Cathy Wong  Medically reviewed by Richard Fogoros, MD 
Updated on March 13, 2020

What Is the Blood Type Diet?

The blood type diet is an eating plan sometimes used in alternative medicine to promote weight loss and fight disease. Alternative medicine aims to recognize an individual’s biochemical uniqueness and tailor treatment accordingly. This plan is based on the theory that your blood type determines the foods you should consume in order to achieve optimal health.

The four different blood types are one marker that can theoretically be used to determine the right diet for your health and vitality. 

What Experts Say

"Basing a diet on your blood type is not evidence-based and restricts many healthy foods. Nutrition experts do not support or recommend this diet for achieving nutrition or health goals."

—Kelly Plowe, MS, RD

The blood type diet was developed by Peter D'Adamo, a naturopathic physician who theorizes that people respond to various foods depending on their blood type. The plan was introduced in his 1996 book "Eat Right 4 Your Type," which was updated with a 20th Anniversary edition in 2016.

The theory behind the diet is that eating foods with lectins (a type of protein) which are incompatible with a person's blood type can cause blood cell clumping, called agglutination, and result in health problems such as heart or kidney disease or cancer. 

D'Adamo also believes that a person's blood type affects their ability to digest various foods due to differences in digestive secretions associated with the different blood types. People who are type O, for example, are thought to digest meat well due to high levels of stomach acid.

By following a meal plan designed for your specific blood type, D'Adamo suggests, you can digest food with greater efficiency, avoid the negative effects of certain lectins, and—in turn—lose weight and enhance your overall health.

How It Works

The blood type diet emphasizes certain foods and exercise plans for different blood types. Regardless of blood type, the diet puts a focus on eating whole foods and minimizing the intake of processed foods. Here's a closer look at the prescribed plans:

- Type A: According to D’Adamo, people with type A blood are predisposed to heart disease, cancer, and diabetes, and do better on an organic, vegetarian diet with calming, centering exercise, such as yoga and tai chi.

- Type B: People with type B blood, according to D’Adamo, have a robust immune system and a tolerant digestive system, and are more adaptable than other blood types. He recommends moderate physical exercise and balance exercises, along with a well-rounded diet. People with type B, however, are more susceptible to autoimmune disorders, such as chronic fatigue, lupus, and multiple sclerosis.

- Type AB: People with type AB blood are more biologically complex than other types, according to D’Adamo. These people do best with a combination of the exercises and diets for types A and B, though meat should be limited. This type tends to have lower rates of allergies, but heart disease, cancer, and anemia are common. 

- Type O: People with type O blood do best with intense physical exercise and animal proteins, while dairy products and grains may cause problems. According to D’Adamo, gluten, lentils, kidney beans, corn, and cabbage can lead to weight gain in this blood type. Health conditions associated with type O include asthma, hay fever, and other allergies, and arthritis.

What to Eat

No foods are completely forbidden on the blood type diet, though not all foods are beneficial for different blood types according to D'Adamo.

Compliant Foods

- Type A: mostly vegetarian—fruits, vegetables, grains, beans, legumes, nuts, and seeds

- Type B: highly varied diet—fruits, vegetables, grains, beans, legumes, meat, poultry, fish, eggs, and dairy

- Type AB: mainly vegan, but any foods recommended for A or B types may be consumed

- Type O: meat with a moderate amount of vegetables, eggs, nuts, and seeds

Non-Compliant Foods

- Type A: meat and dairy

- Type B: nuts and seeds

- Type AB: no specific foods to avoid

- Type O: dairy and grains

People with blood type A, which D'Adamo calls the "cultivator," should follow a dairy-free, primarily vegetarian diet with a high intake of fruits, vegetables, grains, beans, legumes, nuts, and seeds.

People with blood type B, which D'Adamo calls "the nomad," should eat a highly varied diet including fruits, vegetables, grains, beans, legumes, meat, poultry, fish, eggs, and dairy, but avoid intake of nuts and seeds.

People with blood type AB, which D'Adamo calls "the enigma," can consume any food recommended for blood types A and B, although aiming for a mainly vegan diet is advised for this type.

People with blood type O, which D'Adamo calls "the hunter," should stick to a dairy-free and grain-free diet high in meat, low in grains, and with a moderate amount of vegetables, eggs, nuts, and seeds.