Q. Does chelation remove toxic metals and improve health?

A. Injected into the blood, EDTA (ethylenediamine-tetraacetic acid), chelates (binds) toxic metals and allows their removal from the body in the urine. It is used for heavy-metal poisoning, and both IV and oral chelation are also claimed to reduce atherosclerosis and other ailments.

On a Web site for chelation products, I found this case: J.T., age 55, came to Dr. D with monthly recurring small strokes. An arteriogram showed high-grade obstructions in both carotid arteries. Since he started oral chelation six years ago, his strokes have stopped.

However, such case reports or testimonials on commercial Web sites are considered the weakest of scientific evidence, even with hundreds of such reports. You can never be sure of their authenticity.

And because they're used to sell a product, you'll never see negative reports, such as the following two from the August 2006 issue of Pediatrics: In August 2005, a physician intravenously gave a 5-year-old boy IV EDTA as treatment for autism. The boy became limp and died of heart damage from low blood calcium due to EDTA. In August 2003, a healthy 53-year-old woman was given IV EDTA for 10 to 15 minutes to remove heavy metals. After 10 minutes, she became unconscious and died from cardiac arrest.

The sad thing is that well-done research has never shown EDTA or oral chelation to prevent or treat autism, heart disease or anything else. The best studies — randomized experimental ones — fail to show that EDTA improves blood flow, exercise level, or cholesterol in patients with blockages in leg or heart vessels.

In Brazil, a randomized study in 1990 showed benefits, but it was conducted on only 10 patients, and the code for who was in which group was broken before the study's completion, further reducing its accuracy. There are reports of EDTA causing blood clots and insulin shock. And EDTA removes important trace metals such as zinc from the body, which may worsen energy, immunity and cancer risk.

Oral chelation packets may include vitamins, Omega-3 fish oils and other supplements along with EDTA. One brand recommends taking daily two packets containing 25,000 units vitamin A, but randomized studies have shown that taking as little as 33,000 units of vitamin A a day increases deaths from lung cancer, strokes and heart attacks. And there's no evidence that adding other vitamins would help.

So save your money and buy walking shoes instead — chelation may actually do more harm than good.

Dr. Landis Lum is a family-practice physician for Kaiser Permanente and an associate clinical professor at the University of Hawai'i's John A. Burns School of Medicine. Send your questions to Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; fax 535-8170; or write islandlife@honoluluadvertiser.com. This column is not intended to provide medical advice.