"This is the most important study done on dietary supplements since DSHEA was passed," said Dr. Pieter Cohen, an assistant professor at Harvard Medical School who studies supplement safety.
was referring to the Dietary Supplement Health and Education Act, a 1994 law that defined supplements as food rather than drugs.
, who wasn't involved in the study, agreed.
"It's well known that doctors don't ask people about their supplement use," Cohen
"And it's well known that patients don't bring it up."
The U.S. Food and Drug Administration
has limited authority over dietary supplements.
It can take action if a product on the market is found to be unsafe, for example.
But that system, Cohen
said, relies on doctors and consumers to submit reports of harm from supplements.
Also, supplement labels don't have to carry information about side effects.
Nor is there any guarantee that the product contains the ingredients listed on the label -- and only those ingredients, Cohen
In a study published this year, he
colleagues found that nearly a dozen supplements marketed for weight loss were "spiked" with an amphetamine-like substance called BMPEA.
was "not surprised at all" that supplements marketed for weight loss and energy were commonly tied to ER visits in this study.
For now, Cohen
suggested that consumers avoid such combination supplements.
"If you want echinacea, buy echinacea," he
said, referring to the herb that many people believe fights colds.
To find information on the science behind a product, Cohen
recommended the U.S. National Institutes of Health website on dietary supplements.
The U.S. National Center for Complementary and Integrative Health
talks about using supplements wisely.
SOURCES: Andrew Geller, M.D., medical officer, U.S. Centers for Disease Control and Prevention, Atlanta; Pieter Cohen, M.D., assistant professor, medicine, Harvard Medical School, Boston, and internist, Cambridge Health Alliance, Cambridge, Mass.; Oct. 15, 2015, New England Journal of Medicine