Blood type diet proponents believe your blood type affects the types of foods your body can easily digest. Eating the wrong types of foods supposedly causes weight gain, chronic fatigue, immune system problems and other medical conditions. Peter D'Adamo, a naturopathic doctor, designed the diet and authored the book "Eat Right 4 Your Type: The Individualized Diet Solution to Staying Healthy, Living Longer and Achieving Your Ideal Weight." Because the claims of blood type diet advocates are not supported by scientific research, consult a physician before beginning the diet.
Diet Theory
People have different types of proteins marking the surface of their red blood cells. These proteins, called antigens, come in types A and B. Your blood type refers to which of these antigens, if any, your blood cells display. Additionally, some people have an antigen called Rh factor that gives them a "positive" blood type; those without Rh factor have a "negative" blood type.
The theory behind the blood type diet is that the types of antigens on your red blood cells affect the way your body reacts to certain foods. D'Adamo considered the evolutionary history of each blood type to determine the appropriate foods for each type of person to eat.
Type O Negative Blood
People with type O negative blood have neither A nor B antigens on the surface of their red blood cells. They also lack Rh factor, which is not considered important in the blood type diet. In evolutionary history, type O was the original blood type shared by all early humans. These people lived in Africa as hunter-gatherers. So, their diet consisted largely of meat products and certain types of fruits or vegetables.
Foods to Eat
People with type O negative blood should eat meats and fish to incorporate protein into their diet. Organic chicken, turkey, venison and other meats are acceptable foods. D'Adamo recommends O negative individuals eat large amounts of saltwater fish and sea vegetables, which are valuable sources of iodine. People with type O blood should avoid eating grain products, lentils, beans, brussels sprouts, cauliflower, dairy products, cabbage and mustard greens. Acceptable produce includes locally grown broccoli, spinach, kale, onions, red peppers, figs, prunes and plums.
Misconceptions
Although some people like the individualized food plans recommended by the blood type diet, its health claims remain unsubstantiated. Katherine Zeratsky, a nutritionist at Mayo Clinic, says no scientific evidence suggests that the blood type diet can promote weight loss, prevent disease or improve chronic medical problems. To ensure you follow a balanced diet, talk to your doctor to create a meal plan that works for you.
