American Medical Association is against chelation therapy, saying that it is still experimental. However, compared to heart bypass surgery costing $30,000, chelation therapy, at one tenth this cost, seems a bargain.

A. The problem with chelation therapy is not that it's experimental, it's that there's no good scientific evidence that it works.

The idea behind chelation therapy is that the chemical EDTA binds to calcium and other minerals in the blood, which are then eliminated by the kidneys. It is useful only for a very specific problem -- poisoning with lead or other heavy metals.

An estimated 1,000 practitioners in the United States promote EDTA as a treatment for atherosclerosis -- hardening of the arteries. Some also claim that it improves memory, dissolves kidney stones, helps arthritis and fights aging.

Those claims are unproven. Furthermore, the theory behind EDTA treatments doesn't stand up very well. EDTA has never been shown to remove calcium from plaques in arteries. Even if it did, that wouldn't get rid of the plaque itself. Also, any calcium lost from the body is quickly replaced with calcium from the bones. In short, EDTA therapy alone doesn't seem to have any beneficial effects.

Many programs that offer chelation therapy include special diets, exercise and individual support. It's conceivable that these activities, combined with attention and encouragement, improve one's emotional and perhaps physical well-being.

Mainstream medicine's objection to chelation therapy is based on scientific evidence, not economic considerations. But if you want to look at it from a cost perspective, consider this: What's the point of paying several thousand dollars on an ineffective treatment for a life-threatening condition? It doesn't add up.

Follow-Up: Aspirin

Q. For the second time in a few weeks, I've seen you talk about aspirin as a "blood thinner." What exactly does this mean? I've been taking 8 or 10 aspirin tablets a day for the past five years for arthritis. Approximately every two months during this time, I've donated blood to the Red Cross, which they've never rejected as being too thin.

A. Strictly speaking, aspirin isn't a blood thinner like the medicines that can actually keep your blood from clotting. Those medicines, such as heparin (by injection) or Coumadin (by mouth) are powerful anticoagulants used to treat or prevent blood clots in the legs, lung or other parts of the body. Too much of this type of blood thinner can lead to serious bleeding problems, much like those suffered by people with hemophilia.

Aspirin works differently, by decreasing the "stickiness" of platelets. Platelets are what stops bleeding from tiny cuts -- they clump together, plugging up small breaks in blood vessels. Platelets seem to play a role in blocking arteries already narrowed by deposits of plaque. Aspirin, by stopping platelets from sticking to plaque deposits and each other, "thins" the blood in a loose sense and helps prevent two serious complications of blocked arteries: heart attacks and stroke.

Taking aspirin doesn't disqualify you from donating blood. However, people who donate platelets at plasmapheresis centers should stop aspirin at least 72 hours before donating.

It's also a good idea to stop aspirin for two weeks before any scheduled surgery and during pregnancy, especially the last three months.

Jay Siwek, a family physician from Georgetown University, practices at the Fort Lincoln Family Medicine Center and Providence Hospital in Northeast Washington.

Send questions to Consultation, Health Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Questions cannot be answered individually.