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Blood Type Diet

The Blood Type Diet, popularized by the best-selling book Eat Right For Your Type by Peter D’Adamo, ND, is based on the theory that people with different blood types respond differently to specific foods. Dr. D’Adamo’s ideas are rooted in evolutionary history, and, specifically, the observation that different blood types (Type O, Type A, Type B, and Type AB) emerged as the environmental conditions and eating styles of our ancestors changed. Between 50,000 BC and 25,000 BC, all humans shared the same blood type—Type O. These early humans were skilled hunters, and thrived on a meat-based diet. The Type A blood type emerged between 25,000 BC and 15,000 BC, a necessary adaptation to a more agrarian lifestyle. Climatic changes in the western Himalayan mountains led to the appearance of Type B, and the blending of Type A and Type B blood types in modern civilization resulted in the appearance of the Type AB blood type.

Dr. D’Adamo believes that our ancestors’ successful adaptation to environmental changes hinged on the relationship between diet and blood type. As a result, he believes that the key to optimal health is to eat as our ancestors with the same blood type ate. For example, D’Adamo recommends that people with Type O blood eat a diet rich in meat and people with Type A blood follow a grain-based, low-fat, vegetarian diet.

In the Blood Type Diet, foods are divided into 16 categories: meats and poultry; seafood; dairy and eggs; oils and fats; nuts and seeds; beans and legumes; cereals; breads and muffins; grains and pasta; vegetables; fruit; juices and fluids; spices; condiments; herbal teas; and miscellaneous beverages. Foods in these categories are then labeled as “highly beneficial,” “neutral,” or “avoid” according to each of the four blood types.

Why do people follow this diet?

Many people follow this diet to improve their overall level of health. Although weight management is not the focus of the diet, Dr. D’Adamo believes that weight loss is a natural consequence of following a diet tailored to your blood type.

What do the advocates say?

Dr. D’Adamo has spent years researching the physiological effects of substances called lectins. Lectins are proteins found in many commonly eaten foods, particularly the seeds of leguminous plants; they can be absorbed intact from the digestive tract into the bloodstream. According to Dr. D’Adamo, certain lectins are incompatible with certain blood types. This incompatibility allegedly causes the lectin to attract and clump red blood cells, a process known as agglutination. Dr. D’Adamo blames lectin-caused agglutination as the origin of many common health complaints.

Dr. D’Adamo has tested most common foods for blood-type reactions. He organized the results of this testing into food lists that allow people to avoid eating foods containing lectins that are incompatible with their blood type.

What do the critics say?

Some physicians and nutritionists argue that Dr. D’Adamo’s theory about lectins lacks solid scientific support. These critics point out that the research that has been done on lectins has been performed mostly in test tubes. Therefore, it is not yet known what, if any, physiological effects lectins have in humans. Furthermore, many food lectins are destroyed by cooking and/or digestive enzymes, so many critics argue that the number of lectins absorbed intact through the digestive system is minimal. Other critics point out that Dr. D’Adamo’s emphasis on the ABO blood-typing system is somewhat arbitrary. In a book review, Alan Gaby, MD, points out that the ABO system is only one of many different blood-typing methods, and to date, more than 30 unique markers have been identified on the surface of red blood cells. Consequently, if Dr. D’Adamo had based his diet on a different marker, his diet recommendations may have been very different.

Most critics believe the diet is associated with no real health hazards. However, critics caution that people with Type O blood may increase their risk of heart disease by adhering to Dr. D’Adamo’s Type O diet recommendations.

Although most critics concede that the Blood Type Diet produces weight loss in some people, they argue that this diet is merely a calorie-restricted diet. As with any other low calorie diet, weight loss is likely to occur.