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New Study Debunks the 'Blood Type Diet'

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Key Takeaways

  • The “blood type diet,” devised by alternative medicine practitioner Peter D’Adamo in the 1990s, encourages people to base their food choices on their blood type, and claims that some people should eat lots of meat, while others thrive on a plant-based diet.?
  • New research has found that blood type isn’t a factor when it comes to how effective a diet is for weight loss, metabolism, or overall health.

Diets tailored to Type A or Type O blood have been popular since Peter D’Adamo first introduced the so-called "blood type diet" in his 1996 book Eat Right 4 Your Type. But a new study from the Physicians Committee for Responsible Medicine and Yale School of Medicine, published recently in the Journal of the Academy of Nutrition and Dietetics, refutes its supposed benefits.

The blood type diet "claims that your blood type determines which foods, exercise routines, supplements, and lifestyle habits you should follow for overall health. For example, Type A should be mostly vegetarian while Type O supposedly does better on a high protein diet," says Lauren Harris-Pincus, MS, RDN, founder of Nutrition Starring YOU and author of The Protein-Packed Breakfast Club.

Dietitians like Harris-Pincus and other researchers agree, however, that there’s no benefit in basing your diet on your blood type, because it doesn’t affect weight loss, body fat, metabolism, cholesterol levels, blood sugar control, or any other significant health markers.??

Neal Barnard, MD

"Our research shows that all blood types benefit equally from a vegan diet based on the consumption of fruits and vegetables, legumes and whole grains, looking specifically at weight loss and cardiometabolic health in overweight adults."

— Neal Barnard, MD

Study Findings

The researchers studied 244 overweight adults, half of whom were assigned a vegan diet, for 16 weeks, and found that a high-carbohydrate vegan diet could boost metabolism. Those findings were published in November in JAMA Network Open.??

However, the researchers did a separate analysis on the initial results to see if any of the health outcomes were affected by blood type. They found that the health effects of a plant-based diet were consistent, regardless of participants' blood type.

"Our research shows that all blood types benefit equally from a vegan diet based on the consumption of fruits and vegetables, legumes and whole grains, looking specifically at weight loss and cardiometabolic health in overweight adults," said Neal Barnard, MD, lead author of the study and president of the Physicians Committee, in a press release.

Lauren Harris-Pincus, MS, RDN

"[The blood type diet] could be potentially harmful for those with certain medical conditions like diabetes, who need a personalized dietary plan that may be contrary to the recommendations for their blood type."

— Lauren Harris-Pincus, MS, RDN

What's the Problem With the 'Blood Type Diet'?

While there's certainly nothing wrong with trying to make lifestyle changes to improve your health, experts agree that the claims of the blood type diet are not backed by science.

There's no credible peer-reviewed research to support this diet. "People may see success on this diet by simply paying more attention to healthy habits and cutting out highly processed foods, which is recommended for everyone regardless of blood type," Harris-Pincus says. "But this diet could be potentially harmful for those with certain medical conditions, like diabetes, who need a personalized dietary plan that may be contrary to the recommendations for their blood type."

Summer Yule, RDN

"A registered dietitian can let you know if the dietary pattern you are considering is safe, and can work with you to move toward a healthier eating pattern that aligns well with your medical needs, budget, and lifestyle."

— Summer Yule, RDN

Trendy diets like the "blood type diet" might cut out many types of healthy whole foods unnecessarily. "This may put the person at an increased risk of nutrient deficiencies and negatively impact their social lives," says Summer Yule, RDN, a registered dietician based in Avon, Connecticut.

'"A registered dietitian can let you know if the dietary pattern you are considering is safe, and can work with you to move toward a healthier eating pattern that aligns well with your medical needs, budget, and lifestyle," Yule says.

"Each human body is unique and we respond to the foods we eat in different ways," Harris-Pincus adds.

What This Means For You

No matter how popular a diet is, it might not be suitable for you, because no "fad" diet is tailored to individual health needs.

If you're trying to lose weight or improve your health, it's best to consult a registered dietitian who can customize a plan based on your medical history, lifestyle habits, and preferences.

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Article Sources
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  1. Barnard N et al. 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. 2020 Dec. doi:10.1016/j.jand.2020.08.079

  2. Kahleova H et al. Effect of a Low-Fat Vegan Diet on Body Weight, Insulin Sensitivity, Postprandial Metabolism, and Intramyocellular and Hepatocellular Lipid Levels in Overweight Adults: A Randomized Clinical Trial. JAMA Network Open. 2020 Nov. doi:10.1001/jamanetworkopen.2020.25454