Blood type diets gained popularity in America due in large part to naturopathic physician and founder of the Institute for Human Individuality Peter J. D'Adamo, N.D. D'Adamo's bestselling books, including "Eat Right 4 Your Type" and "Live Right 4 Your Type" promote specific diets based on blood type to improve health. According to D'Adamo, people with a B blood type should eat different foods than people with other types of blood, such as A or O. This theory is based on the premise that proteins in your food, called lectins, react with your blood, and that certain lectins are more compatible with some blood types than others.
According to proponents of blood type diets, eating food tailored to your blood type will help you store less fat in your body, fight off and avoid diseases and feel better and healthier overall. D'Adamo also claims that people with different blood types digest lectins, or food proteins, in different ways. Blood type diet enthusiasts also say people should eat the same kinds of foods that their ancestors with similar blood types ate. Since, according to D'Adamo, people with type B blood were traditionally nomads, they should eat a more varied diet than those with other blood types.
What to Eat
D'Adamo's blood type diet does not differentiate between positive or negative blood types. Whether you have B positive or B negative blood, D'Adamo suggests a diet that balances both animal and vegetable selections. Those with B type blood should eat "beneficial meats" such as lamb, goat, rabbit, mutton and venison. B positive and B negative blood types should balance their meat selection with green vegetables, eggs and low-fat dairy.
What to Avoid
For those with type B positive or B negative blood, D'Adamo recommends avoiding wheat, buckwheat, corn, lentils, peanuts, sesame seeds and tomatoes. He asserts that these foods compromise the B blood type group's metabolism and can cause fluid retention, fatigue and hypoglycemia. D'Adamo also notes that the B group should avoid chicken, because it contains what he calls an "agglutinating lectin" that can attack the bloodstream of a person with type B blood and potentially cause immune disorders or strokes.
According to New York University Langone Medical Center, the Blood Type Diet is not supported by scientific evidence. Further concern lies in the fact that certain foods are restricted for certain blood types, making it difficult for the participant to obtain all nutrients necessary for health. The American Academy of Family Physicians similarly criticizes blood type diets, listing them as "fad" diets.
Talk to your doctor about how to maintain a healthy weight and improve your overall health and nutrition, no matter what your blood type. Instead of fad diets, the American Academy of Family Physicians suggests eating a balanced and varied diet incorporating lots of fruits, vegetables and whole grains. Don't skip meals, pay attention to your portion sizes and limit sodium, sugar, cholesterol, trans fat and saturated fat. Finally, engage in physical exercise regularly to stay fit and healthy.