Many popular dietary supplements contain ingredients that may cause cancer, heart problems, liver or kidney damage, but U.S. stores sell them anyway and Americans spend millions on them, according to Consumer Reports.
The consumer magazine published a report on Tuesday highlighting the U.S. Food and Drug Administration's lack of power to regulate such supplements, and said the agency rarely uses what little power it does have.
The report from the influential group urged Congress to speed up small moves toward giving the agency more clout, especially in regulating supplements.
Despite the "natural" labels carried by many of the supplements, many are contaminated.
Yet Americans flock to take them, according to the magazine, citing the Nutrition Business Journal as saying the market was worth $26.7 billion in 2009.
"Of the more than 54,000 dietary supplement products in the Natural Medicines Comprehensive Database, only about a third have some level of safety and effectiveness that is supported by scientific evidence," the report reads.
In addition, the FDA has not inspected any supplement factories in China, even though the agency set up field offices there starting in 2008, Consumer Reports said.
The organization pointed to 12 supplement ingredients in particular that it said could be dangerous: aconite, bitter orange, chaparral, colloidal silver, coltsfoot, comfrey, country mallow, germanium, greater celandine, kava, lobelia, and yohimbe.
Potential dangers include liver and kidney damage, heart rhythm disorders and unhealthy blood pressure levels, it said.
The group is critical of the 1994 Dietary Supplement Health and Education Act or DSHEA, which it describes as industry friendly and which prevents the FDA from regulating supplements in the same way as it regulates prescription medications.
The Federal Trade Commission regulates the marketing of herbal supplements, whose makers are not allowed to claim they treat medical conditions.
The FDA has banned only one supplement ingredient — ephedrine alkaloids — although it has persuaded many companies to pull their products off the market.
"Supplements are marketed with very seductive and sometimes overblown sales pitches for increasing your performance in the bedroom, slimming down, or boosting your athletic prowess," said Nancy Metcalf, senior program editor for the magazine.
"And consumers are easily lulled into believing that supplements can do no harm because they're 'natural'," Metcalf said in a statement.
"However, some natural ingredients can be hazardous, and on top of that the FDA has repeatedly found hazardous ingredients, including synthetic prescription drugs, in supplements."
In May, the Government Accountability Office found that sellers of ginseng, Echinacea and other herbal and dietary supplements often tell consumers the pills can cure cancer or replace prescription medications.
Experts at the Institute of Medicine said earlier this year the FDA needs to use the same strict standards to regulate supplements as it uses for drugs, and the GAO said the FDA should ask Congress for more power to regulate supplements.