The Blood Type Diet: Should You Be Eating According to Your Blood Type?
Key takeaways:
The blood type diet is based on the idea that people react differently to different types of food based on their blood type.
There’s no solid science to support eating according to your blood type.
However, the four blood type diets encourage eating whole foods over processed ones, which is good for your overall health.
Is there a best diet for your blood type? In his 1996 New York Times bestseller, “Eat Right 4 Your Type” (updated in 2016), naturopathic doctor Dr. Peter D’Adamo argues yes. He wrote that people with different blood types have a different internal response to certain types of food. But scientific research tells a different story.
What is the blood type diet?
D’Adamo argued that the four basic blood types — A, B, AB, and O — reflect how people found food in different periods of history. His claim is that eating foods based on your blood type will improve your overall health.
D’Adamo’s book has sold millions of copies, and his website claims that millions of people follow the diet. So, his ideas have reached a widespread audience. But does the blood type diet actually work?
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The author’s website lists anecdotal success stories and book reviews from supposed followers of his eating methods. They say that following the diet for their blood type improved their allergies, energy, and weight loss, as well as conditions like pain and cancer.
Eating for your blood type
According to D’Adamo’s theory, eating for your blood type involves including or avoiding different foods depending on what blood type you have.
The following chart summarizes the recommended diet for each blood type, which we describe in more detail below.
Blood Type | Recommended Foods | Foods to Eat Sparingly or Avoid |
|---|---|---|
Type O (“The Hunter”) | Lean meat, poultry, fish, vegetables | Grains, dairy |
Type A (“The Agrarian”) | Fruits, vegetables, whole grains, legumes, nuts, seeds | Fish, poultry |
Type B (“The Nomad”) | Meat, fruit, seafood, dairy, grains | Nightshade vegetables |
Type AB (“The Enigma”) | Fruits and vegetables, tofu, grains, dairy, fish, lamb, moderate lean protein | Alcohol, caffeine, smoked meats |
Type O diet
D’Adamo called O the oldest of the types, or “the hunter.” The food list resembles a paleo diet, which would be consistent with what hunters used to eat. This diet is:
High in lean meat, poultry, and fish
High in vegetables
Low in grains and dairy (which were less common before farming)
Type A diet
Type A, “the agrarian,” is said to have appeared when agriculture developed. So, the diet recommended for people with Type A blood involves eating:
Mostly plant-based foods (fruits, vegetables, whole grains, legumes, nuts, and seeds)
Small amounts of poultry and fish
Type B diet
Type B is considered “the nomad,” referring to groups who sought different climates. According to the blood type diet plan, people with Type B blood need a balance of different types of food. So, the ideal Type B diet should:
Include a diverse diet of meat, fruit, and seafood, along with dairy and grains.
Include dairy, which is thought to be especially important for this group.
Avoid nightshade vegetables.
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Type AB diet
Finally, D’Adamo calls Type AB “the enigma,” and it’s the most recently developed type. For someone with Type AB blood, eating for your diet would involve a combination of the Type A and Type B diets. This means a Type AB diet would:
Have plenty of fruits and vegetables, tofu, and grains, as well as dairy, fish, and lamb.
Include some lean protein, but in moderate amounts.
Avoid alcohol, caffeine, and smoked meats.
Positive vs. negative blood type
The “positive” and “negative” associated with each person’s blood type (such as “A+” or “O-”) refers to a protein in blood called the Rh factor. According to D’Adamo’s website, this doesn’t play a significant role in the blood type diet.
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Does the blood type diet actually work?
The blood type diet probably doesn’t work — at least not in the way it’s intended. There's currently no evidence to support the idea that your blood type affects how you respond to certain foods. The American Journal of Clinical Nutrition’s review didn’t find any quality studies to prove that following the blood type diet will decrease the risk of disease or improve overall health.
Another scientific review found that some followers of the blood type diet had improved markers of health, like blood pressure and cholesterol. But, very importantly, these results occurred independently of the individuals’ respective blood types. In other words, these improvements were likely due to a diet rich in whole, unprocessed foods — like those encouraged in the blood type diets. The results had nothing to do with a person’s blood type.
Similarly, a study in the Journal of the Academy of Nutrition and Dietetics measured heart function in people following a plant-based diet (as recommended for Type As). It found no difference in results between Type A people versus other blood types. People with Type A and Type O blood types benefited from a vegan diet when it came to heart health. So, the findings didn’t support the blood type diet’s hypothesis.
So, should you eat according to your blood type?
With no concrete evidence to back up the claims of this diet, following the blood type diet isn’t worth the hassle.
That said, one potential benefit of the blood type diet is that it includes eating whole foods that are low in added sugar and sodium. This may explain why followers of the blood type diet report positive changes, even though scientific studies have found no evidence to support eating for your blood type.
So, if you start following the blood type diet, it might lead you to more nutritious food choices in general. But, rather than eating for your blood type or following any restrictive diet, it’s better to focus on an overall balanced diet of nutrient-dense whole foods that are low in added sugar and sodium.
Potential risks of the blood type diet
If you start eating according to your blood type, you may lose out on important nutrients because you’re avoiding certain foods unnecessarily. For example:
Being dairy-free (as recommended for the Type O diet) could make it hard to get sufficient calcium in your diet. Calcium deficiency is associated with increased risk for osteoporosis and problems with normal muscle function.
The diet for Type B encourages avoiding nightshades, which includes eggplant, tomatoes, and bell peppers. These fruits and vegetables contain valuable nutrients. For example, tomatoes and bell peppers are some of the best sources for vitamin C.
The bottom line
There’s no scientific evidence to back up the claim that eating according to your blood type will improve your health. Some people feel that the blood type has helped them. But, most likely, this is because each of the recommended diets involve eating fresh, unprocessed foods. So, if you want to improve your health through diet, you’re better off letting go of the blood type rules and enjoy balanced meals without restriction.
Why trust our experts?
References
Barnard, N. D., et al. (2020). Blood type is not associated with changes in cardiometabolic outcomes in response to a plant-based dietary intervention. Journal of the Academy of Nutrition and Dietetics.
Cusack, L., et al. (2013). Blood type diets lack supporting evidence: A systematic review. The American Journal of Clinical Nutrition.
Office of Dietary Supplements. (2024). Calcium. National Institutes of Health.
Wang, J., et al. (2014). ABO genotype, ‘blood-type’ diet and cardiometabolic risk factors. PloS One.
