The Blood Type Diet is based on the theory that individuals with blood types O, A, B, or AB have distinct nutritional demands. The blood types of your biological parents determine the blood type you have at birth. The presence or absence of two antigens, A and B, on the surface of your red blood cells determines which of the four major blood groups you belong to. For instance, AB blood is obtained by having both antigens, but O blood is obtained by having neither antigen. Your digestive tract contains antigens that are similar to those found in blood, and they determine your blood type—type O, A, B, or AB. Knowing your blood type is the first thing you should do before beginning this diet. If you do not already know your blood type, have a blood test. Your doctor can order a test for you, or you may be able to find out your blood type when giving blood at a blood drive. It’s important to remember that every human red blood cell has a Rh, or Rhesus, factor. If the Rh factor is present in your blood, it will be positive (+) or negative (-). Your blood type group is more important for the Blood Type Diet than whether your blood type is positive or negative.
