Metals naturally accumulate in certain herbs and come from the soil they are grown in. Many supplement ingredients come from Europe, India and China.
"We don't know how much of the ingredients are imported – whether they're coming from across town or across the world," Mister of the trade association conceded.
But even manufacturers get duped, said Jana Hildreth of the Analytical Research Collective, a group of scientists advocating better supplement testing.
"Companies started going to China and demanding lower prices," and unscrupulous suppliers sometimes spiked products with cheap ingredients that can trick lab tests, she said. An example: a buckwheat derivative, rutin, in place of pricier ginkgo.
In ConsumerLab.com testing last November, four out of seven supplements contained less ginkgo than claimed on their labels, and one failed to break apart properly to release its ingredients. Seven out of nine failed in tests in 2003, as did six out of 13 in 2005.
"It is now believed that ginkgo is among the most adulterated herbs," the company reports.
Tests by California scientists of two dozen ginseng supplements, reported in a nutrition journal in 2001, found that many differed from their labels. The concentrations of some ginseng compounds varied by up to 200-fold from product to product.
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.
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.