On Friday, the U.S. Food and Drug Administration announced that starting in late August, manufacturers in the $22 billon-a-year industry must conduct tests to show that their products contain all the ingredients on the label -- nothing more and nothing less.
Companies must also keep records of consumer complaints.
"This will help consumers be more confident that the dietary supplements they take are labeled accurately and free of contamination," said Vasilios Frankos, director of the FDA's Division of Dietary Supplements Programs.
The long-awaited regulations come after years of complaints by consumer advocates that the lightly regulated industry is badly in need of more federal oversight.
Unlike pharmaceuticals and over-the-counter medications, dietary supplements such as weight-loss pills and sports-nutrition formulas are considered food supplements and do not fall under the stricter safety guidelines for drugs.
Studies have found that some dietary supplements do not contain all of the ingredients listed on their labels and that ingredients are often in significantly higher or lower dosages than advertised.
What is more, a number of supplements have been pulled from the market in recent years because they were found to be contaminated with pesticides, metals or other unknown and potentially dangerous ingredients.
Last year, an FDA analysis found instances in which supplements sold to treat erectile dysfunction contained undeclared ingredients that are supposed to be available only by prescription.
Paul Bolar, vice president of regulatory affairs for Pharmavite, the manufacturer of Nature Made vitamins, said the industry welcomed the new regulations because they would help make manufacturing and safety practices more uniform across the board.
"We think this will help consumer confidence in our industry, which is badly needed right now," Bolar said.
The new federal rules go into effect August 24. Companies with 500 or more employees must implement the changes within a year; those with fewer than 20 workers have three years to comply.
FDA officials said that penalties for companies that violate the new rules would vary depending on the severity of the violation.
Companies with minor violations will be given time to make corrections, but bigger problems could lead to products being seized by regulators.
Janell Mayo Duncan, senior counsel for Consumers Union, a New York-based advocacy group, welcomed the new rules but said much more needed to be done to ensure the safety of dietary supplements.
"This is a small, small step in the right direction," she said.
From the July 2, 2007, Prepared Foods e-Flash