Is The Blood Type Diet Legit?

Do you know your blood type? You probably should, just in case of an emergency. (Universal recipient? Score!) Plus, according to the buzzy Blood Type Diet, knowing your blood type is important for more than just your medical records. In fact, it suggests your blood type impacts which foods you need—and which ones you don’t—for better health.

What’s Your Blood Type—And What’s On The Menu?

Your blood type is determined by tiny markers (antigens), which cover the surface of red blood cells. The most common (and likely most familiar) way of classifying these antigens is as follows: A, B, AB, and O. Type A has A antigens, B has B antigens, AB has A and B antigens, and O has neither A nor B antigens (which is why Type O folks are universal donors but can only receive their own blood type).

These antigens exist not just in the blood, but also in other cells throughout the body, including the digestive tract, according to naturopathic doctor Peter J. D’Adamo, N.D., Blood Type Diet founder, author of Eat Right For Your Type, and director of the Center of Excellence in Generative Medicine at the University of Bridgeport.

“The biochemical makeup of humans varies greatly based on blood type,” says D’Adamo. According to D’Adamo, our blood type affects our individual microbiome (and its defining characteristics, like the amount of digestive acid we have to the activity of our digestive enzymes) and therefore how different foods may affect us.

Eating the ‘wrong foods’ for your blood type can produce digestive issues, sluggishness, and weight gain, proposes D’Adamo, blood type dieters may experience improved energy and vitality—and possibly weight loss when eating for their type

The basics of The Blood Type Diet are as follows: People with type A should go vegetarian; Bs should avoid certain foods (including chicken, corn, and tomatoes), ABs should eat small, frequent meals and avoid caffeine and alcohol; and Os should up their meat intake and avoid grain, legumes, and dairy.

As you can already see, many of the diets’ recommendations center around which animal-based foods are or aren’t recommended for your blood type. According to D’Adamo, people with type A evolved to have low levels of stomach acid and high levels of intestinal digestive enzymes, which, together, make it difficult for them to digest animal protein and fat—hence D’Adamo’s suggestion that As go veg. The other blood types, however, have evolved to better metabolize either all or certain meat types, he says.

The diet also recommends certain supplements for each of the blood types, which can be found on D’Adamo’s website. While some of the ingredients are staples for almost everyone—vitamin K, calcium, iron, and manganese­—others are a bit more obscure. Think ‘okra sprouts, bladderwrack seaweed, and gum tragacanth’ level of obscure. (D’Adamo’s book The supplements range in purported function, from helping to optimize metabolism to repairing damage done by eating any foods contraindicated for your blood type.

What the Science Says

The Blood Type Diet hasn’t been proven to work—but it hasn’t been disproven either.

For instance, a 2013 review published in the American Journal of Clinical Nutrition concluded that, at that time, no existing studies on the protocol adequately investigated the effects of following versus not following the diet.

Then, 2014 research published in PLOS ONE found an association between following a type A diet and cardiometabolic benefits, like lower body mass index, waist circumference, blood pressure, cholesterol, and triglycerides. Meanwhile, type AB and O diets were linked with some of those benefits, while no significant connection was found between the Type-B diet and improved cardiometabolic health.

It’s important to note, though, that study participants weren’t assigned to specific diets based on their blood types—so the type A diet showed benefits across participants with A, B, AB, and O blood types. While the study suggests the type A diet (largely vegetarian) specifically may promote health, it doesn’t support the idea that your blood type determines the foods you should and should not eat.

“At this point, we can’t make the necessary link that certain types of diets need to be followed depending on blood type,” explains registered dietitian nutritionist Jessica Crandall, R.D.N., a spokesperson for the Academy of Nutrition and Dietetics. She notes that most improvements in weight and health associated with the Blood Type Diet may be due to dieters becoming more aware of what they are eating as well as prioritizing consumption of whole foods.

“The diet really does focus on cutting out processed foods, which is great and can be beneficial,” she says. However, according to Crandall, one of the diet’s missteps is advising all dieters to avoid all wheat products. Celiac disease, in which a person has an immune response to gluten (the protein in wheat), only affects less than one percent of the U.S. population, according to a consensus statement from the National Institutes of Health.

Related: What Going Gluten-Free Can And Can’t Do For Your Health

Troubleshooting

“I recommend that anyone considering this diet works with a dietitian to determine if it fits your individual needs,” says Crandall. “I’d want to know why they picked this diet, make sure that they get enough protein as well as vitamins and minerals, and also perform blood work to determine any areas where supplementation is needed.”

The Blood Type Diet makes various nutritional supplements specifically for dieters, but Crandall urges that “your blood type isn’t reflective of your blood levels of vitamins and minerals, and, when it comes to supplements, more doesn’t equal better.”

The bottom line: Talk to a professional before embarking on any diet. “You need to make sure that if you choose to follow a Blood Type Diet, you do so in a healthy way,” says Crandall.

Related: Check out a number of supplements to support digestion.

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