The Blood Type Diet: An Evidence-Based Review
Proponents of the blood type diet claim that it can help with digestion, energy levels, and disease prevention

The blood type diet is an eating plan that encourages you to select foods based on your blood type.

Proponents of the diet claim that it can help with digestion, energy levels, and disease prevention, based on the idea that blood type can affect how the body reacts to food and other factors. However, there is not enough scientific evidence to support the health claims of the blood type diet.

Learn about the basic principles of the blood type diet and what the research says about it.

Blood type A diet

About 42% of people living in the United States have blood type A

People with blood type A are recommended to eat a mainly vegetarian, meat-free, plant-based diet. The reasoning behind this is that they have sensitive immune systems and are at higher risk of diabetes, cardiovascular disease, and cancer.

Blood type A requires carbs to maintain overall health. Because of low quantities of hydrochloric acid and intestinal alkaline phosphatase in the stomach, as well as high levels of intestinal disaccharide digestive enzymes, the body can digest and metabolize carbs more effectively than animal protein and fat.

  • Foods to eat with blood type A (organic, fresh foods):
    • Fruits (preferred options include apples, berries, and peaches)
    • Vegetables
    • Legumes
    • Tofu
    • Whole grains 
    • Nuts and seeds
    • Limited intake of beans, turkey, seafood, and dairy, since these can cause insulin reactions
  • Foods to avoid with blood type A:
    • Most meats, especially processed meat
    • All dairy products
    • Wheat
    • Corn
    • Lentils
    • Tomatoes
    • Papayas
    • Mangoes
    • Oranges
  • Meal frequency/portion sizes: Eat normal portions
  • Recommended exercise: Mix of strenuous and relaxing exercises (yoga, tai chi, brisk walking, and swimming)

Blood type B diet

About 10% of people living in the United States have blood type B. 

People with blood type B are adaptable and can obtain nutrients from both animals and vegetables. However, maintaining balance is critical. People with this blood type tend to be physically and psychologically more fit than those with any other blood type.

They are encouraged to eat a diet rich in vegetables and meat, as well as a limited amount of dairy. Because people with blood type B have a stronger immune system and tolerant digestive system, they appear to be able to withstand chronic illnesses better than those with other blood types.

  • Foods to eat with blood type B:
    • Green vegetables
    • Fruits
    • Eggs
    • Low-fat dairy
    • Meat (except chicken and pork)
    • Legumes
    • Grains
  • Food to avoid with blood type B:
    • Corn
    • Wheat
    • Buckwheat
    • Lentils
    • Tomatoes
    • Peanut
    • Sesame seeds
    • Chicken
    • Pork
    • Rye
    • Peanuts
  • Meal frequency/portion size: Can eat larger portions (high-calorie is acceptable)
  • Recommended exercise: Combination of vigorous and relaxing exercises. Responds best to moderate exercise that combines physical and mental endurance

SLIDESHOW

Diet-Wrecking Foods: Smoothies, Lattes, Popcorn, and More in Pictures See Slideshow

Blood type AB diet

Only about 4% of people living in the United States have blood type AB. People with this blood group are believed to have a higher risk of stomach cancer than those with other blood groups.

People with blood type AB have low stomach acid levels and should therefore consume smaller, more frequent meals. They may benefit from combining different food combinations but should avoid combining carbs and proteins at the same time. This will assist them in effectively digesting and metabolizing meals. 

People with blood type AB are recommended to eat tofu, seafood, dairy, and green vegetables.

  • Foods to eat with blood type AB:
    • Seafood and lamb
    • Tofu
    • Fruits
    • Eggs
    • Dairy
    • Grains
    • Seeds and nuts
  • Foods to avoid with blood type AB:
    • Smoked and cured meats
    • Caffeine
    • Alcohol
    • Corn
    • Beef
    • Buckwheat 
    • Refined sugars
    • Red meat
    • Pork
    • Kidney and lima beans
  • Meal frequency/portion size: Small, frequent portions
  • Recommended exercise: Tension-relieving activities and moderate-intensity exercise. Responds best to calming and spiritual exercises

Blood type O diet

About 44% of people living in the United States have blood type O. 

Blood type O is said to be the "original" blood type, having originated from hunter-gatherers. Therefore, people with this blood type are recommended to eat a hunter-gatherer diet, which resembles the paleo diet and is high-protein and gluten-free.

People with blood type O have high stomach acid levels and are more able to digest protein and fat. Cholesterol derived from animal products can also aid in digestion and calcium absorption.

  • Foods to eat with blood type O:
    • Lean meat, fish, and chicken
    • Fruits
    • Vegetables
    • Limited intake of grains, beans, eggs, legumes, and dairy
  • Foods to avoid with blood type O:
    • Cabbage
    • Cauliflower
    • Caffeine
    • Alcohol 
    • Carbohydrates
    • Refined sugars 
    • Nuts 
    • Grains (primarily wheat and corn)
  • Meal frequency/portion size: Moderate (smaller) proportions
  • Recommended exercise: Vigorous and intense exercise. Responds best with intense physical exercises (Jogging, martial arts, contact sports, and biking are advised for an hour a day.)

QUESTION

According to the USDA, there is no difference between a “portion” and a “serving.” See Answer

What is the role of lectin in the blood type diet?

Lectin is a type of protein present in grains, nuts, seeds, and legumes that bind sugar molecules. According to a few theories, they may interfere with digestion and absorption of nutrients in the body. They also have agglutinating qualities, which affect your blood.

Claims

According to a few nutritionists, when we consume foods containing lectins, a chemical reaction occurs in the blood that causes blood cells to clump together which can lead to hormonal disruptions.

Some nutritionists claim that people with different blood types will react differently to particular foods and their lectins. When eating foods that contain lectins that are not compatible with your blood type, the lectins may target an organ or bodily system and begin to agglutinate blood cells in that area. The blood type diet is designed to target these factors.

Facts

There is no evidence that lectins affect people differently based only on their blood type. In reality, research has shown that lectins do not promote blood clumping as some nutritionists claim. 

Lectins are found in about 30% of our diet, many of which are nutritious plant-based foods high in antioxidants, fiber, vitamins, and minerals. It is not necessary to eliminate an entire group of healthy foods, particularly when these suggestions are based on theory rather than substantial proof.

Fortunately, most lectins in the average diet are not harmful to the body, since most are cooked off before consumption. The immune system also sloughs off 95% of the lectins consumed in a typical diet.

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What are the potential benefits of the blood type diet?

Each subtype of the blood type diet is low in processed foods and added sugars and recommends the consumption of lean meat, fruits, and vegetables, which are good for overall health. This focus on eating clean foods can help lower inflammation and protect against disease.

Despite the lack of proof supporting the diet as a whole, there are components of the blood type diet that are backed by research. For example, plant-based foods have been shown to help with healthy weight management and reduced risk of disease.

What are the potential downsides of the blood type diet?

Nutritional guidelines in the blood type diet can be restrictive and are not necessarily cost-effective, since it may require specialty and organic products.

Furthermore, the blood type diet does not take into account individual health issues and simply offers suggestions based on blood type. The diet can lead to nutrient deficiencies and even encourage harmful eating behaviors. 

Instead of following the blood type diet, it is better to consume a wide variety of nutrient-dense foods and make healthy choices that are sustainable and realistic. 

What do studies say about the blood type diet?

There is little research supporting the idea that eating for a specific blood type affects health.

According to nutritionists from the American Council on Science and Health, there is no consistency or logical reasoning behind this diet because it makes broad generalizations about billions of people and minute details about how they should eat.

  • According to a 2013 review of studies on the blood type diet published in the American Journal of Clinical Nutrition, no evidence exists to support the supposed health advantages of the diet.
  • In another 2013 review published in the journal PLOS, researchers investigated the effect of blood type diets on heart disease indicators such as triglycerides, insulin, cholesterol, and blood pressure and discovered that blood type diets did show some beneficial changes in those risk factors. These findings, however, were connected with better food quality and were not assumed to be related to eating for a certain blood type.
  • A thorough review by the Belgian Red Cross reported that there is no evidence to support the advantages of the blood type diet. However, because the diet is restrictive, it may lead to weight loss
  • A 2014 study reported that people following blood type diets had better health outcomes, including improvements in weight, cholesterol, and blood sugar management. However, the same health effects were observed in unmatched blood type groups. This suggests that the health benefits of following the diet are not exclusive to people of a specific blood type. 
  • A 2018 study published in the Journal of Nutrition found that the blood type diet did not have any significant health effect on overweight adults.

Does knowing your blood type affect your health?

Although there is no current data to show that blood type groups benefit from specific diets, there is some evidence that particular blood types may make people more or less vulnerable to specific illnesses.

  • Stress: If you have blood type A, you may have a harder time coping with stress. People with blood type A tend to have elevated levels of cortisol.
  • Heart disease: People with blood type O are the least likely to get heart disease. People with blood types AB and B are more at risk, which may be due to increased levels of inflammation associated with these blood types. 
  • Cancer: Studies suggest that those with blood types A or AB are more likely to get stomach cancer. Furthermore, if you have blood types A, B, or AB, you may be at a high risk of pancreatic cancer.

The bottom line

Knowing your blood type is simply one way to better understand your risk for certain diseases and make adjustments accordingly. Although your blood type is hereditary that cannot be changed, adopting healthy choices can help you prevent or avoid health risks.

There is no scientific evidence to support the blood group diet. While there may be some short-term benefits, most of the health claims surrounding the diet are based on theory rather than concrete data. As a result, further study is required to determine whether there are legitimate benefits of the blood type diet.

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Medically Reviewed on 7/27/2022
References
Image Source: iStock image

Blood type diets lack supporting evidence: a systematic review: https://pubmed.ncbi.nlm.nih.gov/23697707/

New Study Debunks Blood Type Diet: https://www.pcrm.org/news/news-releases/new-study-debunks-blood-type-diet

The Blood Type Diet: https://www.webmd.com/diet/a-z/blood-type-diet

Does Science Support the Blood Type Diet? https://foodrevolution.org/blog/does-science-support-the-blood-type-diet/

The Right Type of Diet: A Thesis on the potential relations between your blood type and the way you eat: https://scholarlycommons.obu.edu/cgi/viewcontent.cgi?article=1253&context=honors_theses