Q. Is there any scientific proof behind the blood type diet?

A. Many health experts -- rightly so -- emphasize the importance of customizing health guidelines to the individual. And naturopath Peter J. D'Adamo, N.D., takes an interesting spin on this idea in his book, "Eat Right 4 Your Type" (Putnam, 1996), in which he claims that diet, exercise and stress reduction should all be based on the four basic blood types: O, A, B, and AB. He purports that lectins, a group of proteins found in foods, can create negative reactions with your blood, thus promoting health problems.

The solution to the problem? People should avoid foods that are incompatible with their blood types, says D'Adamo. People with type O blood should follow an intense physical exercise program with a diet focusing on animal proteins. Those with blood type A are better suited to an organic, vegetarian diet and a calming exercise such as yoga. If you're a type B, D'Adamo urges moderate physical exercise and eliminating problematic foods such as corn, wheat and chicken. People with blood type AB should follow a combination program of type A and B, with a focus on foods like seafood and yogurt. By following this program, D'Adamo reports that you will feel better, lose weight and improve your health.

There's no doubt that the blood type diet is intriguing; D'Adamo mines the fields of anthropology and genetics to create a fascinating backdrop for each blood type diet. He traces people with blood type A all the way back to their roots in Africa as game meat supplies dwindled; type B he connects with Himalayan ancestry. While D'Adamo's blood type diet is an interesting theory, many health experts find a few holes in it.

One problem is the lack of science behind the idea that people with different blood types should eat differently. There is evidence that blood types carry a higher risk of certain conditions (for example, blood type O is linked with higher risk of stomach cancer.) D'Adamo claims that about 75 percent of people following the blood type diet for at least a month report health improvements, but this is self-reported data.

We are not aware of any clinical trials that evaluate the efficacy of the blood type diets on weight loss or health. Many of the recommendations make sense (i.e., include exercise and stress reduction), but some of the dietary guidelines can be restrictive and do not account for food preferences. For example, you're out of luck if you are a vegetarian with type O blood. The American Dietetic Association puts the blood type diet on their fad diet list. Let's wait for the science to catch up with the emerging research on personalized eating strategies.

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