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The Blood Type diet is a way of eating that relies on an individual’s blood type (A, B, AB, or O) to dictate one’s diet. In his 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 him and which foods are not. The book presents the anthropological origins of each of the four blood types and explains why each blood type developed specific antibodies against certain foods.
Antibodies are proteins within the blood that identify and attack substances that are foreign to the body. Specific proteins called lectins are found in all foods. During digestion, lectins are released from the foods eaten. When they enter the blood stream, some of these lectins can bind to red blood cells causing them to stick together. This process is called agglutination. Dr. D’Adamo suggests this process causes many health problems such as stomach pains, poor digestion, headaches, diarrhea, liver disease, and kidney problems, and more.
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. Dr. D’Adamo reports that following this diet will not
(Illustration by GGS Information Services/Thomson Gale.)
only improve health but will help achieve an ideal weight
In 1901, Dr. Karl Landsteiner discovered that there were four types of human blood. He named them A, B, AB, and O. He discovered that blood types are not compatible with each other because of antibodies. These antibodies cause blood to clump together if a different blood type is mixed with it. According to Dr. D’Adamo, it was also discovered that foods can cause blood cells to become sticky and clump together in a process called agglutination.
Dr. D’Adamo’s father, James, is also a naturopathic physician noticed that different diets worked better with some patients than others. In his book, One Man’s Food—Is Someone Else’s Poison, he attributed this to the differences in blood type.
Dr. Peter D’Adamo continued his father’s research by studying the agglutination process that occurs between specific blood types and certain foods. He believes it is the result of the evolution of the unique blood types.
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. Dr. D’Adamo suggests 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 to meat were formed. According to Dr. 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. The diet included both meats and plants as well as dairy products. Dr. D’Adamo believes this is the reason individuals with blood type B developed fewer antibodies against lectins found in meat and grain. He also believes this is why people with blood type B are more tolerant of milk products than other blood types.
The final blood type to evolve was type AB. It is a rare blood type even today with fewer than 5% of the world’s population having type AB blood. Type AB evolved when the A and B blood types intermingled. Dr D’Adamo describes this blood type as a complex blood type with many strengths and many contradictions.
D’Adamo divides all foods into sixteen food groups.
The food groups are:
- Meats and poultry, pork, and chicken Seafood-fish and shellfish
- Dairy and eggs—milk, yogurt, ice cream, cheese, and eggs
- Oils and fats—all oils such as peanut oil, linseed oil, sesame oil, etc
- Nuts and seeds—all nuts or seeds
- Beans and legumes—all beans and peas
- Cereals—oats, barley, cream of wheat, corn flakes, puffed rice, etc
- Breads and muffins—all baked goods such as loaf breads, crackers, etc
- Grains and pasta—all flour, buckwheat, all noodles, spaghetti, etc
- Vegetables—all vegetables, olives, peppers, and avocado
- Fruit—fresh fruits, dried fruits, and canned fruits
- Juices and fluids—all fruit juices fresh and concentrate
- Spices—all spices fresh and dried, syrups, miso, soy sauce, and other sauces that are not dairy based
- Condiments—mayonnaise, mustard, ketchup, jellies and jams, pickles, pickle relish,and salad dressing
- Herbal teas—all herbal teas
- Miscellaneous beverages—coffee, black tea, green tea, seltzer waters, colas, wine, beer, and liquor
Within each of the sixteen food groups, he describes individual foods as foods that encourage weight gain, foods that encourage weight loss, beneficial foods, neutral foods, and foods to avoid. In this way 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 and is found on the foods to avoid list for individuals with blood type B and blood type AB. Another example is grains such as wheat. Dr. D’Adamo reports there are no wheat products that are beneficial for people with type O blood. They are to be avoided. Similarly, he advises individuals with type B blood to avoid wheat as well. On the other hand wheat is highly beneficial for people with blood type A and neutral for those with blood type AB. There are recipes and sample menus for each blood type as well.
In addition to specific and detailed dietary guidelines, Eat Right for Your Blood Typealso includes advice for each blood type concerning the impact of stress on the body and strategies for coping with stress.
Dr. D’Adamo outlines the best supplements for each blood type and addresses the best form of exercise for individuals of each blood type.
The Blood Type diet is based on the fact that all foods have lectins, or proteins that can interact with antibodies in blood. Dr. D’Adamo has tested most foods and determined which blood types react adversely to lectins in most foods.
When a specific food’s lectin reacts with a specific blood type (A, B, AB, or O), it causes a process called agglutination to occur. In agglutination, the lectins cause the blood to become sticky. Dr. D’Adamo believes these sticky blood cells can lead to medical conditions such as impaired digestion, kidney and liver problems, headache, diabetes, obesity, and many others.
In order to reverse the problems caused by agglutination, an individual must avoid or limit the consumption of foods that cause it. Dr. D’Adamo has tested foods to determine which foods react adversely with which blood types. By following the Blood Type diet, these foods and the offending lectins may be avoided, and health may be improved.
In addition to the main blood types of A, B, AB, and O, there are many subtypes. These are other factors that are contained within your blood. These additional subtypes include secretor status and Rh. Rh is the part of blood that determines if a blood type is positive or negative. The Rh factor of blood type is not affected by diet; however, when blood type is reported, it is usually given as well.
Secretor status does influence the role diet plays in the functions of the body. Secretor status refers to whether or not blood type antigens, the part of the blood that determines type, are in other fluids of your body such as saliva and urine. Approximately 80% of all people are secretors. For these people, blood type can be determined by testing other bodily fluids. In the remaining 20% of the population, blood type antigens are found only in the blood. According to Dr. D’Adamo, secretors are more sensitive to interactions with food lectins. Secretors would have a more severe reaction over more systems in the body than non-sectretors. There is a test to determine if an individual is a secretor; however, since 80% of the population are secretors, chances are that most people who attempt the Blood Type diet are secretors.
Dr. D’Adamo reports health benefits in his patients that follow the Blood Type diet. His official website is full of testimonials from satisfied Blood Type diet followers. Not only do they report weight loss, but, according to Dr. D’Adamo, each blood type is more susceptible to certain illnesses than the others.
According to Dr. D’Adamo, the benefits of following the Blood Type diet for people with blood type A include weight loss and a reduced risk of heart disease, cancer, anemia, liver and gallbladder disorders, and type I diabetes.
For individuals with blood type B, the benefits if following the Blood Type diet include weight loss and a reduction of the risk of type I diabetes, chronic fatigue syndrome, and auto immune disorders such as Lou Gehrig’s disease, lupus, and multiple sclerosis.
People with blood type AB who follow the Blood Type diet may lose weight and have a reduction in the risk of developing heart disease, cancer, or anemia.
For individuals with blood type O, following the Blood Type diet may help them lose weight and may prevent blood clotting disorder, inflammatory diseases such as arthritis, hypothyroidism, ulcers, and asthma.
Even critics of the diet suggest that features of the diet such as limiting the amount of saturated fat and highly processed “junk foods” will benefit most people.
Since blood type is a fixed characteristic of an individual, it never changes. Following a diet based on blood type would theoretically never need to change. However, there are many medical conditions that change as a person ages. Diseases may develop such as diabetes, hypertension (high blood pressure), and heart disease that may require an individual with type O blood to reduce consumption of meat and increase intake of fruits and vegetables. Following this diet may be harmful if variations in the diet necessary for health maintenance are not allowed.
Encouraging a specific blood type to gradually increase dairy consumption may cause discomfort to individuals with a natural lactose intolerance, regardless of blood type. Conversely limiting diary can lead to poor calcium intakes and bone related diseases.
Certain individuals with protein deficiency or anemia may need to consume more meat to insure sufficient protein consumption, regardless of blood type.
Unbalanced diets put one at risk of nutritional deficiencies or long term poor intakes that will affect
one’s health. This risk and the fact that there is no scientific evidence to back up the claims needs to be emphasized more strongly Since there is no data that confirms the efficacy of this diet for individuals with medical conditions that require careful monitoring of diet. Individuals with diseases such as diabetes, coronary artery disease, compromised liver function, or any kidney disease may not be able to follow a diet tailored for blood type alone.
While many followers of the Blood Type diet report improved health and weight loss, the Blood Type diet is not widely accepted. Dr. D’Adamo cites many anthropological and microbiological studies to support his theories. However, critics argue there is virtually no data to support his diet plan. They charge that he has no well designed, well control studies to validate his claims that blood type is critical to the impact of diet. Noting that he has not conducted simple before and after blood studies to demonstrate his claim that lectin protein in foods cause blood cells to agglutinate or stick together.
Furthermore, they argue, if agglutination were as wide spread and common as Dr. D’Adamo claims, thousands of people would die each year from organ failure caused by this process and that pathologists would easily see evidence of this. Yet, no such evidence is presented or found in a review of the literature.
Additionally, critics argue that reducing people to a set of criteria based solely on blood type is tantamount to biological astrology. Characterizing all blood type O individuals as hunter-gatherers who need meat and blood type A individuals as more passive agrarians who will benefit most from a nearly vegetarian diet, they argue is far too simplistic for beings as genetically diverse and complex as humans.
There have been no controlled studies comparing those who follow the Blood Type diet with those who do not, or those who follow other diets. Dr. D’Adamo cites studies that demonstrate the effect of specific food lectin on animals such as rabbits which develop symptoms similar to arthritis when lentil lectins are injected into the knees of those sensitive to lentil lectins.
Dr. D’Adamo reports he has tested lectins from most common foods against individual blood types to determine which blood types are sensitive to the lectins of which foods.
Similarly, he reports measuring the impact of lectins on his patients by using the Indian Scale, a measure of the effectiveness of the bowels. Higher values on the Indian Scale indicate reduced function of the liver and intestines and increased levels of toxins. Dr. D’Adamo reports that the Indian Scale scores of his patients have decreased significantly after following the correct Blood Type diet.
Dr. D’Adamo cites multiple individual case studies of patients he has treated using the Blood Type diet with great success.
D’Adamo, Peter M.D with Allan Richards. One Man’s Food—Is Someone Else’s Poison. Toronto, Ontario, Canada: Health Thru Herbs (1994).
D’Adamo, Peter J. M.D. and Catherine Whitney. Cook Right for Your Blood Type: The Practical Kitchen Companion to Eat Right for Your Blood Type Berkley, CA: Berkley Trade, 2000.
D’Adamo, Peter M.D. with Catherine Whitney. Eat Right For your Type: The Individualized Diet Solution to Staying Healthy, Living Longer, and Achieving your Ideal Weight . New York, NY: G. P. Putnam and Sons, 1996.
D’Adamo, Peter J. M.D. and Catherine Whitney. Live Right for Your Blood Type New York, NY: Putnam Adult, 2000.
D’Adamo, Peter J. M.D. and Catherine Whitney. The Eat Right for Your Blood Type Encyclopedia New York, NY: G. P. Putnam and Sons, Riverhead Books, 2002.
Nomi, Toshitaka and Alexander Besher. You Are Your Blood Type New York, NY: St. Martin’s Press, 1983.
Muschel, L. “Blood Groups, Disease and Selection” Bacteriological Rev” 30, no. 2 (1966): 427–441
Freed, D. L. F. “Dietary Lectins and Disease.” Food Allergy and Intolerance (1987): 375–400.
Freed, D. L. F. “Lectins.” British Med. J. 290 (1985): 585– 586.
Whman, L. C. and W. C. Boyd. “Human Blood Groups and Anthropology.” Amer Anthropol 37 (1953): 181.
Frazier Roberts, J. A. “Some Associations between Blood Types and Disease.” Brit Med Bull 15 (1959): 129–133.
The Institute for Human Individuality. The official Website of the Blood Type Diet, it contains more information about the diet, forums, email access to Dr. D’Adamo, scientific data, training opportunities for nutritionists and doctors, and a listing of Blood Type Diet practitioners. April 19, 2007, URL: http://www.dadamo.com.
Deborah L. Nurmi, MS.