Over 150 of the tested supplements contained more than one unapproved ingredient.
Of the adulterated products, almost 46 percent were for sexual performance, 41 percent were for weight loss and 12 percent were for building muscle. Further, poison control centers evidently received over 1,000 reports of adverse reactions to dietary supplements over a span of three years.
With an estimated 50 percent of Americans consuming some type of supplement, researchers note that the $35 billion industry is a big business.
From 2007 to 2016, the lion's share of FDA warnings - 46 percent - concerned supplements that touted enhanced sexual pleasure, while weight-loss products were cited in 41 percent of the warnings.
The products contained a number of pharmaceuticals, including the active ingredient in Viagra (sildenafil), as well as sibutramine - an appetite suppressant that was taken off the market because of links to strokes and heart attacks.
When the FDA finds a supplement product that contains potentially hazardous ingredients, such as undeclared active pharmaceuticals, the agency said it works to remove it from the market.
One previous study associated dietary supplements with 23,000 emergency department visits and 2,000 hospitalizations each year in the United States.
Dietary supplements aren't regulated like pharmaceutical drugs, so that means they shouldn't contain pharmaceutical drugs.
The FDA has identified the tainted over-the-counter products, but according to new research published Friday in JAMA Network Open, over half the time, the study found, the FDA doesn't enforce recalls of supplements that knowingly include unapproved prescription drug ingredients.
Researchers at the California Department of Public Health combed through a Food and Drug Administration database of contaminated supplements for 2007 to 2016. And nearly all of the muscle-building supps contained synthetic steroids or steroid-like ingredients - the long-term side effects of overuse include liver, kidney, and mental health issues to name just three.
However, less than half of these products were recalled after the FDA learned of their contents, which has left the federal agency facing criticism for failing to pursue companies that are selling the misleading supplements.
Cohen, an associate professor of medicine at Harvard Medical School, believes that "more than FDA action will be required to ensure that all adulterated supplements are effectively and swiftly removed from the market".
"Only 360 of 746 (48%) were recalled, leaving the majority of adulterated supplements, more than 350 products, available for sale", Cohen wrote in an editorial published with the study. Officials with the FDA are cracking down on e-cigarette companies and warning that some products could be removed from the market, The Hill reported. Another would give the FDA tougher enforcement tools so that a product's registration could be withdrawn if found to be adulterated.
"Despite these challenges, the FDA recognizes the seriousness of this problem and continues to act within its resources and authorities to address this problem as best it can", a FDA spokesman said.
Supplements spiked with drugs pose a number of health risk to consumers - the drugs might interact with other medications that a person is taking; or they may be unsafe for people with certain health conditions.