The Blood Type Diet: Exactly What You Need To Know According To A Functional Medicine Expert

blood type

In 1996, a naturopathic physician named Peter D’Adamo published the book Eat Right 4 Your Type, which gave diet and lifestyle advice based on blood type. Immediately, it was a massive success, selling over 7 million copies, making the New York Times bestseller list, and translated into 52 different languages. (1) 

Now, decades later, it’s still incredibly popular, despite the hundreds of nutrition and lifestyle books that have come after it. But what is the science behind the blood type diet? Does it really make sense? Read on for my thoughts.

What is the blood type diet? 

The basic theory behind the diet is that our blood type creates differences in our physiology that are substantial enough to warrant adjustments in lifestyle. For example, on his website D’Adamo describes Type O as the “oldest of the blood types” writing that those with type O blood display traits like “exceptional strength, a lean physique, and a productive mind” but also an “overactive fight or flight response reminiscent of early survival instincts.” He then goes on to say that type A blood types entered the genetic landscape at the time of animal domestication and agriculture. “Thriving on a mostly vegetarian diet rich in soy protein, fruits and vegetables, Blood Type A individuals are sensitive, creative, analytical thinkers,” he writes.  

According to a Harvard Health Blog (2) on the topic, the Blood Type Diet gives the following recommendations for each blood type: 

  • Those with type O blood should choose high-protein foods and eat lots of meat, vegetables, fish, and fruit but limit grains, beans, and legumes. To lose weight, seafood, kelp, red meat, broccoli, spinach, and olive oil are best; wheat, corn, and dairy are to be avoided.
  • Those with type A blood should choose fruit, vegetables, tofu, seafood, turkey, and whole grains but avoid meat. For weight loss, seafood, vegetables, pineapple, olive oil, and soy are best; dairy, wheat, corn, and kidney beans should be avoided.
  • Those with type B blood should pick a diverse diet including meat, fruit, dairy, seafood, and grains. To lose weight, type B individuals should choose green vegetables, eggs, liver, and licorice tea but avoid chicken, corn, peanuts, and wheat.
  • Those with type AB blood should eat dairy, tofu, lamb, fish, grains, fruit, and vegetables. For weight loss, tofu, seafood, green vegetables, and kelp are best but chicken, corn, buckwheat, and kidney beans should be avoided.

If this all seems a little far-fetched to you, you wouldn’t be the first to think so. In fact, one german scientist is quoted as saying “it is difficult not to perceive the whole thing as a crass fraud.” (3)


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What is the science behind the blood type diet? 

The Blood Type Diet claims to help the body function ideally by supporting healthy digestion and high energy levels. D’Adamo even says that by following your Blood Type Diet plan, you can prevent diseases like cancer and cardiovascular disease. Research has been done on the blood type diet, but none of it was conclusive. For example, a 2013 study (4) analyzed existing medical literature on the benefits of these diets and found no benefit; another study published in 2014 showed that people following any of the blood type diets experienced improvements in cardiometabolic risk factors (5) like cholesterol and blood pressure but that these improvements could actually be linked to blood type. Not to mention, research has also come out proving that type O is not actually the most ancient blood type — type A is (6). Unfortunately, when you dive deeper into the basis of the Blood Type Diet and the research behind it, there are quite a few gaps and holes. 

That said, there is also research showing that certain blood types do put humans at risk for specific health issues. For example, the authors of a 2011 study (7) concluded that “...studies have conclusively linked the ABO locus to pancreatic cancer, venous thromboembolism, and myocardial infarction...These findings suggest ABO's important role in determining an individual's susceptibility to such diseases.” In addition, certain foods do seem to affect blood types differently. For example, the lectins found in raw lima beans cause issues in those with type A blood (8) but not with other blood types. 

Therefore, it’s not a huge leap to say that in the future, when we know more about each blood type, we’ll find that certain food sensitivities are, in fact, more common in some than in others. That said, the research to back up the very specific recommendations that D’Adamo gives in his book just doesn’t exist. 

What are my thoughts on the Blood Type Diet? 

From where I’m sitting, the nutrition and lifestyle advice in the Blood Type Diet is universally healthy, regardless of blood type. For example, D’Adamo advocates for eating real, whole foods and avoiding universally inflammatory foods like dairy, wheat, and certain lectin-containing beans and legumes. He also takes a holistic approach to healthy, giving tips for exercise and stress management. Personally, I’m all for that, there are plenty of other factors that affect our health after all.

Therefore, if you want to follow the blood type, it won’t hurt. In fact, it may benefit your health in more ways than one — just know that the benefits don’t appear to be connected directly to your blood type.

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  1. University of Toronto. (2014, January 15). Theory behind popular blood-type diet debunked. ScienceDaily. Retrieved August 27, 2020 from
  2. Shmerling, R. H. (2017, May 12). Diet not working? Maybe it’s not your type - Harvard Health Blog. Retrieved August 28, 2020, from Harvard Health Blog website:
  3. Artikler, S. alle. (n.d.). ”Blodtypedietten” – vitenskap eller fantasi? Tidsskrift for Den Norske Legeforening. Retrieved from
  4. Leila Cusack, Emmy De Buck, Veerle Compernolle, Philippe Vandekerckhove, Blood type diets lack supporting evidence: a systematic review, The American Journal of Clinical Nutrition, Volume 98, Issue 1, July 2013, Pages 99–104,
  5. Wang, J., García-Bailo, B., Nielsen, D. E., & El-Sohemy, A. (2014). ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors. PLoS ONE, 9(1), e84749.
  6. Shouse, B. (2011, September 29). Why Do We Have Different Blood Types? Live Science. Retrieved from
  7. Yamamoto, F., Cid, E., Yamamoto, M., & Blancher, A. (2012). ABO research in the modern era of genomics. Transfusion medicine reviews, 26(2), 103–118.
  8. Nathan Sharon, Halina Lis, History of lectins: from hemagglutinins to biological recognition molecules, Glycobiology, Volume 14, Issue 11, November 2004, Pages 53R–62R,

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Dr. Will Cole, IFMCP, DNM, DC, leading functional medicine expert, consults people around the world via webcam and locally in Pittsburgh. He received his doctorate from Southern California University of Health Sciences and post doctorate education and training in functional medicine and clinical nutrition. He specializes in clinically researching underlying factors of chronic disease and customizing a functional medicine approach for thyroid issues, autoimmune conditions, hormonal imbalances, digestive disorders, and brain problems. Dr. Cole was named one of the top 50 functional medicine and integrative doctors in the nation and is the best selling author of Ketotarian and The Inflammation Spectrum.