Antioxidant supplements may also prevent any of the health gains that normally come from exercise, such as increased insulin sensitivity.

Makers of dietary supplements cannot legally say that dietary supplements can diagnose, cure, treat, or prevent disease.

Under F.D.A. rules, manufacturers may not claim that their supplements can treat or prevent disease.

There was no support for claims that the supplements prevented colorectal cancer, and plenty of evidence that they actually caused kidney stones.

She's also joined a Rush University Medical Center study to see if an antioxidant supplement can prevent Alzheimer's disease.

The supplements prevent cavities in permanent teeth.

Certain nutritional supplements such as vitamin C and the bioflavonoids can strengthen the tone of blood vessel walls and prevent hemorrhoids in other ways.

Some bodybuilders taking steroids also take antiaromatase supplements to prevent excess testosterone conversion into estrogens, which can cause gynecomastia.

The study, whose results are being reported today, also found no evidence that the supplements prevented colorectal cancer, and it found an increased risk of kidney stones.

If you want to take supplements to prevent cancer, talk to your doctor about what is safe for you to take.