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Food for Your Blood?

Eating by blood type.

WebMD Feature
Reviewed by Craig H. Kliger, MD

July 24, 2000 -- When Michelle Murdock and her husband sit down for dinner together, they never eat the same meal. While she doesn't eat meat, her husband eats it often. She loves peanut butter; he avoids it. She shies away from dairy products, while he consumes all the milk and cheese he wants. Why do their menus vary so widely? It's not because they have different tastes -- rather, they have different blood types. (Hers is type A; his is type B.)

The Murdocks follow the "Eat Right for Your Type" diet, which encourages people to consume certain foods and shun others based on their status of A, B, AB, or O. Michelle, 29, has been on the diet for almost two years and is still enthused. "I lost about 35 pounds the first year I was on it," she says. ''I have since maintained a healthy weight." She says she has the energy of a teenager.

Who'd think a diet would be based on blood type? The theory is the brainchild of Peter J. D'Adamo, ND, a naturopathic physician in Stamford, Conn., who touted the program in his 1996 book, Eat Right for Your Type, which gave the diet its name. Eating this way can not only keep you healthy and help you lose weight, D'Adamo says, but not eating this way can harm you, perhaps setting you up for digestive problems or serious ailments, including cancer. Not everyone agrees with D'Adamo -- the diet is roundly criticized by most mainstream nutritionists and medical doctors for the lack of published evidence showing it works.

But criticism is not enough to deter as many as two million people who follow the diet (the figure comes from D'Adamo and is based on visitors to his web site and his private practice). These blood-type diet fans don't mention feeling deprived because of food restrictions, but talk instead about how good they feel. Many, like the Murdocks, embrace the diet as a new lifestyle.

The Diet's Theory

One reason for these dieters' enthusiasm is that there's no counting of calories or fat grams. Instead, the diet emphasizes eating certain foods, in any quantity you'd like. For instance, Type O's are advised to eat meat but no grains. Type A's should be vegetarians. Type B's can eat the most varied diet, including meat and dairy products. And Type AB's should eat some meat, but lay off cured or smoked meats.

Why are certain foods specified for each blood type? D'Adamo believes that lectins, proteins found in foods, can wreak havoc in the body. If you eat a food containing lectins that are not compatible with your blood type, he says, the lectins can target an organ or system in the body. This can adversely affect blood cells in the area and possibly cause disease, including kidney disease and cancer. However, these negative effects can be avoided by focusing on foods that mesh with your blood type, D'Adamo says.

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