Blood Type Diet

The Blood Type diet is a fad diet that claims that an individual's blood type (A, B, AB, or O) can affect diet and health. In his 1996 book, Eat Right for Your Blood Type, naturopathic doctor Peter D'Adamo presents the idea that an individual's blood type determines which foods are healthy for that person and which are not. The book describes the anthropological origins of each of the four blood types and explains why each blood type develops specific antibodies against certain foods.

D'Adamo's father, James, also a naturopathic physician, noticed that different diets worked better with some patients than others. In Peter D'Adamo's 1994 book, One Man's Food—Is Someone Else's Poison, he attributed this difference to the differences in blood type. Peter D'Adamo continued his father's research by studying the agglutination process that occurred between specific blood types and certain foods. He maintained that it was the result of the evolution of the unique blood types. In 2001, he founded the Institute for Human Individuality, an institution with the goal of fostering education and research in nutrigenomics and epigenetics.

Anthropologists have traced the origins of each blood type. The earliest human blood type was type O. Since these people were ancient hunter-gatherers and ate a diet dominated by meat, blood type O individuals developed antibodies against the lectins found in agricultural foods such as wheat and other grains. D'Adamo suggested that individuals with type O blood should eat a diet more similar to their ancient ancestors—that is, a diet with more meats and fewer grains.

The next blood type to evolve was type A. As the environmental conditions changed, humans began to grow food rather than hunt it. The diet shifted from predominantly meat to plant-based. As the diet changed and the blood type A evolved, antibodies for lectins in meat were formed. According to D'Adamo, individuals with blood type A have antibodies against many lectins found in meat and will benefit from a largely vegetarian or plant-based diet.

The next blood type to emerge was type B. As ancient peoples migrated and adapted to further climate change, blood type B evolved. Their diet included meats, plants, and dairy products. D'Adamo claimed this was the reason individuals with blood type B developed fewer antibodies against lectins found in meat and grain. He also maintained this was why people with blood type B were more tolerant of milk products than other blood types.

The final blood type to evolve was type AB. It remains a rare blood type, with fewer than 5% of the world's population having type AB blood. Type AB evolved when the A and B blood types intermingled. D'Adamo described this blood type as a complex blood type with many strengths and many contradictions.

The Blood Type diet includes extensive lists of foods that are beneficial for each blood type. The food lists also include foods that each blood type should avoid and foods that are neutral or benign. D'Adamo reports that following this diet will not only improve health but will help individuals achieve an ideal weight.

The Blood Type diet divides all foods into 16 food groups:

Within each of the 16 food groups, there are foods that promote weight gain, foods that support weight loss, beneficial foods, neutral foods, and foods to avoid. The diet is unique and individual for each blood type. For example, chicken is considered neutral for individuals with blood type O and blood type A. However, it is on the foods-to-avoid list for individuals with blood type B and blood type AB.

In addition to specific and detailed dietary guidelines, Eat Right for Your Blood Type also includes advice for each blood type concerning the impact of stress on the body and strategies for coping with stress. D'Adamo outlined the best supplements for each blood type and addressed the best form of exercise for individuals of each blood type.

D'Adamo presented another approach to dieting in the 2007 book, The GenoType Diet: Change Your Genetic Destiny to Live the Longest, Fullest and Healthiest Life Possible. The book divides people into six genetic categories (GenoTypes). Similar to the Blood Type diet, each GenoType category has an eating plan of foods to emphasize, foods to limit or avoid, and neutral foods.

Blood type is one of the criteria used to determine a person's GenoType. According to D'Adamo, the six GenoTypes are:

There is a food list for each GenoType. Foods in the book are categorized as “superfoods to emphasize” and “toxins to limit or avoid.” Superfoods that provide additional benefits are marked with a diamond. Food in the Toxins list with a black dot may be added to the diet in moderate amounts three to six months after the person has been on the diet. Neutral foods, or those that do not have nutritional benefits for that GenoType, are the remaining foods that are not on either list. D'Adamo also makes recommendations for supplements, stress reduction, and exercise.

The Blood Type diet was built on the fact that all foods have lectins, or proteins that can interact with antibodies in blood. D'Adamo believes that when a specific food's lectin reacts with a specific blood type (A, B, AB, or O), it can cause agglutination to occur. In agglutination, the lectins cause the blood to become sticky, and D'Adamo asserts that these sticky blood cells can lead to medical conditions including obesity, impaired digestion, kidney and liver problems, headache, and diabetes. The Blood Type diet claims to reverse this process by eliminating the foods that cause agglutination. The GenoType diet is based on a similar premise, with diet activating “good” genes and shutting down “bad” genes. However, all of D'Adamo's claims are speculative and are not supported by scientific evidence.

D'Adamo claims that people who follow his diets will lose weight and reduce their risk of developing certain diseases. There is no proof behind these claims and they are not supported by the scientific community; however, critics do agree that certain aspects of the diets, such as limiting the amount of saturated fat and highly processed “junk” foods, will benefit most people.

The Blood Type and GenoType diets are considered fad diets and are not generally supported in the scientific and medical communities. People should consult with their physician before beginning any weight loss plan, including the Blood Type or GenoType diet. This is especially true for pregnant and breastfeeding women. These diets restrict many healthful foods, including certain fruits, vegetables, and proteins. These foods are considered to be part of traditionally accepted dietary recommendations, such as the 2010 Dietary Guidelines for Americans issued by the U.S. Department of Agriculture (USDA) and the Department of Health and Human Services (HHS). Other foods that the guidelines caution about limiting (such as fats) are acceptable in larger quantities on the Blood Type and GenoType diets.

People with certain conditions, such as diabetes, hypertension, heart disease, or food allergies, may be at higher risk of adverse side effects if following the Blood Type and GenoType diets. People with these and other conditions should never change their diets without first discussing the changes with their physician. People taking prescribed medications should also not stop taking medications unless approved by their doctor.

While many followers of the Blood Type diet reported improved health and weight loss, the Blood Type diet has drawn some criticism, primarily that there is virtually no data to support the plans. There have been no well-designed, well-controlled studies to validate the diet claims, and critics assert that if agglutination was as widespread and common as D'Adamo claims, thousands of people would die each year from organ failure caused by this process. No such evidence has been presented or found in reviews of the literature. Similar criticisms have also been made of the GenoType diet.

Although it is recognized that there is a relationship between genetics and obesity, the workings of this relationship are not yet fully understood. According to the U.S. Centers for Disease and Prevention (CDC), the best course of prevention for people genetically predisposed to gaining weight is a combination of a healthy diet, physical activity, and, if needed, medication. Pharmaceutical companies have begun using genetic approaches (pharmacogenomics) to develop new drug strategies to treat obesity, according to the CDC.

See also Dietary guidelines ; Fad diets ; Nutrigenomics .