The idea behind the diet plan in Eat Right 4 Your Type, also called the blood type diet, is that following a diet and lifestyle that suits your blood type will make you healthier, help you reach your ideal weight, and even slow down the aging process. That’s according to the author of the book Eat Right 4 Your Type, the naturopathic physician Peter J. D’Adamo, MD. Eat Right 4 Your Type was originally published in 1996 and quickly hit major bestseller lists, and since then, Dr. D’Adamo has published a number of books on the diet, including Live Right 4 Your Type and Change Your Genetic Destiny. “The concept of the Eat Right 4 Your Type diet is that blood types have evolved through the evolution of man,” says Chicago-based David Grotto, RD, author of The Best Things You Can Eat. The thinking goes that “most [people] were type O — hunter-gatherers with a predominantly animal-protein-based diet.”
D’Adamo says that protein components in food called lectins bind with antigens on blood cells and lead to blood cell clumping, or agglutination. Avoiding agglutination, D’Adamo argues, can improve health by helping people manage weight better and fight cancer and heart disease. Liz Weinandy, RD, at the Ohio State University Wexner Medical Center in Columbus, Ohio, says that lectins can be dangerous to our health if eaten in large amounts, but the way D’Adamo presents their effects may be misleading. Reducing their potential health harms is relatively easy: For example, lectins found in dried beans can be eliminated simply by soaking the beans in water for a few hours and then boiling them for 10 minutes, Weinandy says. But D’Adamo uses his theory to develop separate diets for people with blood types A, B, AB, and O. In addition, he recommends exercise and overall healthy habits, like drinking enough water, Weinandy explains. However, the diet is specific about which foods are allowed for different blood types — and that can be restrictive, Weinandy says. In fact, while people often have different nutritional needs, humans are complex animals, and chalking up these specifics to blood type may oversimplify those needs, Weinandy says. “To base a whole diet on that is probably not very sensible,” she says.
While Eat Right 4 Your Type might help with weight loss, as any calorie-restricted diet would, whether it has more significant health benefits than another eating approach is another matter entirely. Critics of the plan argue there is little to no science to back up the theory that eating according to blood type can improve your health. “What do clumping blood cells have to do with weight? I can understand heart disease and risk for blood clots,” Grotto says, “[but] as far as I know, there is no science to support the connection of agglutination and obesity, cancer, and so on.” Weinandy agrees, noting that many of the claims in the book are not scientifically proven. In fact, one article found no support for the blood type diet’s claims that adherence could improve health and lower the risk of chronic disease. (1) Researchers analyzed surveys from 1,455 study participants and found that while some people benefited from sticking to a particular diet, this was actually independent of their blood type. For example, people following the type A diet tended to have a lower body mass index (BMI) and blood pressure than other study participants, regardless of whether they themselves had type A, type B, type AB, or type O blood.
Here is a sample one-day diet for each blood type, based on D’Adamo’s recommended recipes: (6)
“I have no problems with the blood type A recommendations, which is a plant-based diet,” says Grotto. “Overall, the recommendations are good for most of the blood types.”
Also, the Eat Right 4 Your Type diet does help people reduce calories and can lead to weight loss. “Unlike a lot of other fad diets, the general advice is good,” Grotto says. “I have dealt with patients who say they feel better after following the diet.”
But there is some evidence that people with certain blood types may be more prone to certain illnesses. For instance, “individuals with type O blood may be at a greater risk for duodenal ulcers. Those who are type A may be at an increased risk for atrophic gastritis,” says David J.A. Jenkins, PhD, MD, the Canada research chair in nutrition and metabolism at the University of Toronto. Some blood type O patients have specific proteins that are attacked by the bacteria Helicobacter pylori, which is commonly linked to ulcers.
Similarly, that bacteria has also been associated with atrophic gastritis, though the exact relationship between type A blood and atrophic gastritis is not known.
But there’s no evidence to support the theory that eating a diet tailored to a certain blood type has any effect on these conditions, Dr. Jenkins says.
There’s concern that the Eat Right 4 Your Type diet for those with blood type O is too protein-heavy. “Animal protein, especially red meat, has been linked to health problems, such as heart disease and colorectal cancer,” says Grotto.
Also, dietitians say it’s possible that individuals may experience nutritional deficiencies when following the eating plan.
“The Eat Right 4 Your Type diet recommends calcium supplements for [type O and type A individuals] who can’t eat dairy, for example,” says Amy Jamieson-Petonic, RD, a pediatric and sports dietitian who is based in Ohio. “But you can only absorb a certain amount of calcium from supplements, and you get so much more from food. If you follow this diet for a long time, you could experience vitamin and mineral deficiencies.”
Another potential long-term problem with the blood type diet is a drawback common to many diets: Restriction leads to boredom. “When you take away favorite foods, it’s almost a death knell for any dietary program, whether there is solid advice or not,” Grotto says. “If you tell people to avoid fruit or anything made with white flour, they can go back to those foods with a vengeance later on.” Some critics argue that Eat Right 4 Your Type places too much emphasis on blood type and fails to take into account individual differences. “I would look at an individual’s food preferences and health challenges, such as stroke risk, hypertension, and allergies,” Grotto says.
“Whatever you do to lose weight, it has to be reasonable to be sustainable,” Weinandy says. She notes that the blood type diet may work for some people, but given how restrictive it is, people may have trouble sticking with it long term — and thus not be able to keep off the weight they lost.
Still, for people curious about the benefits of the blood type diet, Weinandy sees no harm in trying it for a short period of time. “More important, make sure that you are eating wholesome foods that are not processed,” she advises, noting that she often directs patients more toward a Mediterranean diet or a DASH diet for overall health and weight loss.
Additional reporting by Stephanie Bucklin.
Editorial Sources and Fact-CheckingEveryday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Kayli Anderson has over a decade of experience in nutrition, culinary education, and lifestyle medicine. She believes that eating well should be simple, pleasurable, and sustainable. Anderson has worked with clients from all walks of life, but she currently specializes in nutrition therapy and lifestyle medicine for women. She’s the founder of PlantBasedMavens.com, a hub for women to get evidence-based, practical, and woman-centered guidance on nutrition and cooking, hormone health, fertility, pregnancy, movement, mental well-being, nontoxic living, and more. Anderson is board-certified in lifestyle medicine and serves as lead faculty of the American College of Lifestyle Medicine’s (ACLM) "Food as Medicine" course. She is past chair of the ACLM's registered dietitian member interest group, secretary of the women's health member interest group, and nutrition faculty for many of ACLM's other course offerings. She is the coauthor of the Plant-Based Nutrition Quick Start Guide and works with many of the leading organizations in nutrition and lifestyle medicine to develop nutrition content, recipes, and educational programs. Anderson frequently speaks on the topics of women’s health and plant-based nutrition and has coauthored two lifestyle medicine textbooks, including the first one on women’s health, Improving Women's Health Across the Lifespan. She received a master's degree in nutrition and physical performance and is certified as an exercise physiologist and intuitive eating counselor. She's a student of herbal medicine and women's integrative and functional medicine. She lives with her husband in the Colorado Rocky Mountains, where you’ll find her out on a trail or in her garden.
Katherine Lee is a writer and editor who specializes in health, science, and parenting content. She has written for Verywell, where she covered school-age parenting, and worked as an editor at Parenting and Working Mother magazines. She has written and edited numerous articles and essays on science, parenting, and children's health and development for What to Expect, the American Association for the Advancement of Sciences, the American Psychological Association, and Newsweek, among others
