Now, medical experts are calling on the FDA to take more urgent action to remove these tainted supplements from the market.
The presence of unknown drugs in supplements "poses a serious public health risk", the researchers wrote.More than 50 percent of the USA population consumes dietary supplements, and many consumers mistakenly believe the products are carefully regulated and accurately labeled.
"The agency's failure to aggressively use all available tools to remove pharmaceutically adulterated supplements from commerce leaves consumers" health at risk", Dr. Pieter Cohen, a general internist at Cambridge Health Alliance in Somerville, Massachusetts, wrote in a commentary accompanying the study. "The FDA didn't even bother to recall more than half of the potentially hazardous supplements".
In an interview, Daniel Fabricant, president of the Natural Products Association, a supplement industry trade group, said it is unfair to consider sexual enhancement, weight loss and muscle building products in the same category as traditional dietary supplements such as vitamins.
The greatest number of products found to contain hidden ingredients were reported in 2009, when two large recalls together named 99 products.
Some of these contained a cut-rate downgrade of the advertised ingredients, but of much more grave concern, numerous supplements that were marketed as 'natural, ' contained often-experimental versions of pharmaceutical drugs.
The active ingredients in Viagra, Cialis and Levitra - widely found in the sexual enhancement supplements - can interact with nitrates found in medicine prescribed for diabetes, high blood pressure and high cholesterol and can dangerously lower blood pressure, the researchers said. During that period, 776 supplements marketed for muscle building, sexual enhancement, or weight loss were found to contain prescription drugs, such as the stimulant ephedrine, anabolic steroids, and selective serotonin reuptake inhibitors (SSRIs) commonly prescribed to treat anxiety and depression, as well as the active ingredients in erectile dysfunction drugs Viagra and Cialis, to name a few.
Previous research by Cohen and colleagues has found that supplements continue to be sold in stores even after they are recalled.
It should be noted that the findings are limited to drugs for which the FDA tested, a number and variety that is not disclosed in the study. And "all of the ones that are not recalled will remain on the market".
Admittedly, voluntary recalls don't work particularly well, but Dr Cohen says that the FDA rarely reaches into its deeper toolbox to issue mandatory recalls or go to the Justice Department. Or the FDA may have contacted these companies, but they refused to voluntarily recall their products. In all, a total of 146 companies were implicated. "The drug ingredients in these dietary supplements have the potential to cause serious adverse health effects owing to accidental misuse, overuse, or interaction with other medications, underlying health conditions, or other pharmaceuticals within the supplement". Sibutramine, widely found in the weight loss products, can substantially increase blood pressure and pulse rate. Instead, the FDA only gets involved after a supplement has been shown to be harmful, at which point the agency can issue a recall.
A 2015 study found that dietary supplements are tied to 23,000 emergency room visits and 2,000 hospitalizations in the USA each year. If the company refuses to recall the product, the agency should follow up with aggressive actions to make sure the product is not available to consumers. "The FDA has to dedicate appropriate resources to getting the job done", Cohen said. That way, each supplement would have a registration code to identify it, which would allow the FDA to know exactly what supplements are being sold in the country.
"We're completely on the FDA's side here", said Fabricant, who worked at the federal agency regulating supplements earlier this decade.
But in the meantime, there are steps consumers can take to protect themselves from tainted supplements. If people choose to start taking supplements without medical advice, Cohen recommends "single-ingredient" supplements rather than supplements with mixtures of ingredients, and to avoid supplement that promise health benefits like weight loss.