For years, the fitness supplement industry has taken advantage of its lack of government oversight by offering products that not only tout unrealistic results, but often, don’t even contain the ingredients listed on the bottle. Now a new study conducted by the FDA has revealed that hundreds of supplements sold in stores actually contain unlisted and unapproved pharmaceutical drugs that could lead to a wide variety of negative health effects for consumers.

The U.S. Food and Drug Administration (FDA) is under no legal obligation to test the veracity of claims made by supplement manufacturers, nor do they even test supplements for safety unless faced with overwhelming evidence suggesting a threat exists. As a result, companies offering products like “weight loss” stickers and “testosterone boosting” pills that are often filled with little more than corn flour have flooded the market. It’s not just the ludicrous seeming supplements that aim to fool the customers, however, with protein powders and similarly basic supplements often found to contain unlisted ingredients once subjected to an independent third party analysis.

However, the revelation that many of these supplements also contain trace amounts of unrelated pharmaceutical drugs is a significant development; moving the actions of supplement manufacturers out of the realm of snake-oil salesmen and into a far more egregious class of criminal enterprise. With more than 20,000 supplement-related visits to the Emergency Room in the United States per year, it stands to reason that the lack of federal oversight into the supplement market may be harming the American people far more than these products claim to help them.

“The agency’s failure to aggressively use all available tools to remove pharmaceutically adulterated supplements from commerce leaves consumers’ health at risk,” Harvard’s Dr. Pieter Cohen wrote in a response to the FDA’s study published in the medical journal JAMA. The study identified 746 brands of supplements that were, as Cohen puts it, “adulterated with pharmaceutical agents — but more disturbingly, only about half of those supplements identified were pulled off the shelves as a result. Cohen explains:

Most supplements adulterated with drugs were marketed as weight loss, sexual enhancement, or sports supplements—the same categories that epidemiologists have found to be responsible for a disproportionate number of the estimated 23,000 emergency department visits attributed to dietary supplements each year in the United States.

More than 20 percent of those 750 identified supplements including more than one unregulated drug, and in some cases, as many as six different pharmaceuticals were found in a single product.

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“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,” another group of medical professionals explained in a peer reviewed analysis of the FDA’s findings.

The most common drugs found in these supplements were prescription anti-depressants, erectile dysfunction medications, and even the weight loss drug sibutramine — which was withdrawn from the market by Abbott Laboratories in 2010 after clinical trials showed its use led to a higher risk of stroke and myocardial infarction.

Currently, the federal government has no plans to begin meddling with the $35 billion per year supplement industry in the United States, meaning their announcement that many of these supplements contain illegal prescription drugs was perhaps meant more as an advisory than anything else. For those who frequently use supplements as a part of your fitness regimen, experts suggest seeking third party lab analysis of the supplements you choose to ingest. Two prominent examples of independent labs that rate supplements are Labdoor and ConsumerLab.