GNC, the country's largest retailer of supplements, has agreed to pay $2.25 million in a settlement with the Department of Justice.
It's part of an ongoing federal crackdown on supplements that contain hidden drug ingredients, harmful compounds or that don't truthfully list their ingredients.
The popular store chain has also agreed to better police the products it sells, weeding out pills and potions that contain illegal and unsafe ingredients, and keeping a list of safe-to-sell products.
GNC did not admit to any wrongdoing in the settlement, but the Department of Justice said it would keep open the threat of prosecution if GNC breaks any promises.
"A lengthy investigation conducted by the U.S. Food and Drug Administration (FDA), the U.S. Attorney's Office for the Northern District of Texas and the Consumer Protection Branch of the Department of Justice's Civil Division revealed that GNC's practices related to ensuring the legality of products on its shelves were lacking," the DOJ said in a statement.
"GNC engaged in acts and omissions that allowed a misbranded supplement — OxyElite Pro Advanced Formula, a product of Dallas-based USPlabs LLC (USP Labs) — to be sold at GNC locations nationwide in 2013."
GNC did not know that the capsules contained anything other than what the label said, but also didn't bother to check, the DOJ said.
In 2015, authorities indicted USPLabs for falsely claiming its popular workout and weight loss supplements were made using natural ingredients.
Some of USPLabs' products contained 1,3-dimethylamylamine — or DMAA. It's sometimes called a geranium extract on product labels. Two soldiers died after taking DMAA, which can cause heart attacks. It also caused an outbreak of liver injuries that were severe enough to require liver transplants.
"Companies like GNC need to do more to ensure that they are not selling products containing questionable and untested ingredients," said Benjamin Mizer, head of the Justice Department's Civil Division.
"GNC will maintain and continuously update a list of ingredients that will be prohibited from inclusion in any products that are sold by GNC," the DOJ said.
The company will also spend $500,000 training farmers who supply herbal and botanical products, the Justice Department said.
The multibillion dollar vitamin and supplement industry operates with very little regulation because the 1994 Dietary Supplement Health and Education Act (DSHEA) exempts products from FDA's pre-marketing oversight.
According to the National Center for Health Statistics, more than half of Americans took some sort of dietary supplements in 2003-2006, 40 percent of them multivitamins.