Tests Show Many Supplements Have Quality Problems

In ConsumerLab.com tests, six out of nine chondroitin supplements failed testing in April 2007. One had only 8 percent of what it claimed to contain, and one "maximum strength" product had none.

Vitamins and minerals had problems, too. A "high potency" iron supplement contained less than half the amount claimed. Of 23 top-selling vitamin C pills, one provided less than half the amount promised; the suggested dosages of some others were beyond recommended safe levels. Of 10 vitamin A supplements, one provided twice its stated amount, raising concern about toxic side effects.

Last year, nearly 200 people were sickened by supplements containing up to 200 times the amount of selenium stated on the label. Symptoms included hair loss, discolored and painful fingernails, muscle cramps, joint pain, diarrhea and fatigue.

Hidden Prescription Drugs
The FDA has repeatedly warned about herbal pills found to contain versions of Viagra and similar drugs to help men get an erection. These can pose a heart hazard, especially when taken with certain medications.

In December, the FDA expanded warnings about dozens of brands of weight loss pills. Though the labels did not say so, some contained sibutramine, a controlled substance that poses heart risks; rimonabant, a drug not approved in the United States; a seizure medicine, and a diuretic.

Red yeast rice, a traditional Chinese medicine, has compounds that may block cholesterol in a way similar to statin drugs. Some red yeast rice products have been found to contain lovastatin, the active ingredient in the drug Mevacor. Problems can occur at high doses or with other medicines.

Other Risks
Even "safe" supplements can be harmful. Beta-carotene takers still had increased rates of lung cancer six years after one study was stopped. These supplements "appear to increase rates of the disease, particularly among smokers," the National Cancer Institute warns.

In another study, men taking vitamin E were slightly more likely to get prostate cancer, and those taking selenium were a little more likely to develop diabetes. The results could have been due to chance, but federal officials were taking no chances and stopped the study last October.

Other studies suggest that high doses of vitamin C may help shield cancer cells from treatments designed to kill the cancer.