The Blood Type Diet suggests that an individual’s nutritional needs are determined by their specific ABO blood group. This approach claims that eating in alignment with one’s blood type can lead to better health outcomes, increased energy, and weight management. For Blood Type B Positive individuals, this dietary framework outlines specific restrictions across various food groups that should be eliminated due to perceived incompatibility.
The Theory Behind Dietary Avoidance
The central concept underpinning this diet is the reaction between blood type antigens and proteins called lectins, which are present in many foods. Lectins are sugar-binding proteins that, according to the theory, can interact negatively with the specific antigens found on the surface of red blood cells. For Type B individuals, the presence of the B antigen is believed to make them vulnerable to certain lectins.
When an incompatible lectin is consumed, it is theorized to cause a reaction known as agglutination, where blood cells begin to clump together. This clumping is claimed to interfere with digestion, metabolism, and the overall immune system, potentially leading to inflammation. The dietary restrictions are designed to prevent this agglutinating effect and optimize bodily functions.
Restricted Grains and Legumes for Type B
Grains and legumes represent one of the most heavily restricted categories for individuals following the Type B diet plan. Wheat and its derivatives are considered particularly problematic because they contain a lectin believed to interfere with Type B metabolism, potentially leading to sluggishness and weight gain. This avoidance extends to common items like whole wheat bread, whole wheat flour, and other products containing wheat germ or bran.
The diet also specifies several other grains and legumes for elimination:
- Corn and buckwheat, as the lectins in these grains are theorized to be highly incompatible with the Type B blood factor.
- Rye, barley, and various processed cereals that are based on these disallowed grains.
- Most lentils, including red and green varieties, alongside specific beans such as adzuki, black, and pinto beans.
- Peanuts and derived products like peanut butter, due to the particular lectins they contain.
Meats, Poultry, and Seafood to Limit
The Type B diet places specific restrictions on certain animal proteins, with poultry being a primary focus for elimination. Chicken is listed as a food to avoid because the theory suggests its muscle tissue contains a lectin that can be agglutinating to the Type B blood type.
Pork and its cured forms, such as bacon and ham, are also recommended for avoidance. While Type B individuals are generally encouraged to eat a varied, omnivorous diet that includes red meat, the diet advises limiting or avoiding specific cuts and processed meats. In the seafood category, all shellfish, including crab, shrimp, mussels, clams, and lobster, are listed for elimination. The avoidance of these meats and seafood is rooted in the idea that their proteins may promote inflammation or be difficult for the Type B digestive tract to process efficiently.
Scientific Perspective on Diet Efficacy
Despite its widespread popularity, the Blood Type Diet is not supported by mainstream nutritional science. A systematic review of the existing medical literature found no empirical evidence to validate the purported health benefits of eating according to one’s ABO blood type. Major health and scientific organizations do not endorse the diet, and the core claim regarding lectin-induced agglutination affecting health has not been clinically proven outside of D’Adamo’s theoretical model.
Any positive health changes or weight loss experienced by followers are generally attributed to the fact that the diet promotes the elimination of highly processed foods, refined sugars, and simple carbohydrates. When individuals adopt a diet that emphasizes whole, unprocessed foods, health markers often improve regardless of blood type. The scientific consensus is that a diet’s overall nutritional quality, rather than its alignment with a blood group, determines its efficacy.