Food for Your Blood? (cont.)

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.

D'Adamo also theorizes that a person's ability to digest foods varies depending on blood type. For instance, he claims that Type O's can efficiently digest meats because they tend to have high levels of stomach acid. Type A's, he says, have low stomach acid and store meat as fat.

D'Adamo bases his theories on research he's conducted since the early 1990s on the connections among blood type, food, and disease. He says his research builds on work done by his father, a naturopathic physician who drew on his observations of his patients. Based on those observations, D'Adamo also suggests that type O's should exercise vigorously, B's moderately, and A's gently. AB's, he says, need calming exercise.

Where's the Beef?

While D'Adamo acknowledges that there is no scientific study that demonstrates that his program helps with weight loss or disease prevention, he has posted 52 pages of references on his web site (www.dadamo.com) that he says back up his belief that blood type may be related to disease. But many mainstream nutritionists and medical doctors roundly criticize the program and urge their patients not to follow it. These critics cite the lack of published studies showing that the diet works.

"My initial skepticism of the diet plan was supported by the complete lack of scientific foundation [in D'Adamo's book]," says John McMahon, ND, a naturopathic physician in Wilton, Conn. "I believe he feels he is doing people a favor, but I think he is seriously mistaken."

Adds John Foreyt, PhD, a weight loss researcher at the Baylor College of Medicine in Houston: "I know of no plausible rationale behind the diet."