Experts found unnamed ingredients in common supplements for muscle building and sexual health.

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Whether they want to lose weight or build muscle, many people rely on supplements to give them an edge as they pursue their health goals. However, a recent investigation shows that these common supplements may contain ingredients you wouldn’t expect — and you won’t find them listed on the bottle.

In a report published in JAMA Network Open this month, researchers analyzed the tainted dietary supplements database from the Food and Drug Administration’s Center for Drug Evaluation and Research from 2007 through 2016. They found that 776 dietary supplements, sold over the counter and online, contained unapproved ingredients.

The vast majority of the supplements evaluated by the study were marketed for one of three things: sexual enhancement (about 46 percent), weight loss (41 percent), or muscle building (12 percent). These supplements were found to be adulterated with potentially dangerous substances.

“There’s no guarantee that what’s in the bottle is the same as what the bottle says is in there. Manufacturers are getting ingredients for supplements from all over the place and there are so many points where something that’s not supposed to be there could be added,” said Dr. Arielle Levitan, coauthor of “The Vitamin Solution,” and cofounder of Vous Vitamin.

For example, many weight-loss supplements in the study contained sibutramine, a drug that increases the risk of cardiovascular issues and was removed from the United States in 2010. The majority of muscle building supplements were tainted by unlabeled anabolic steroids, the report said. And sexual potency drugs often contained sildenafil — the active ingredient in Viagra.

While not all of these adulterants are inherently dangerous, they have the potential to cause harm if taken at the wrong dose or in conjunction with other drugs.

“It’s not that all the drugs are bad — they’re great at what they’re supposed to do — but they need to be given in a safe and regulated way that doctors can monitor,” added Levitan.

A 2017 survey commissioned by the Council for Responsible Nutrition found that 76 percent of adults in the United States take dietary supplements — an all-time high. Almost 9 out of 10 respondents said they had confidence in the “safety, quality, and effectiveness” of supplements.

So why do so many supplements fail to live up to the high confidence displayed by consumers? It goes back to a misunderstanding of how these products are regulated, said Dr. Joseph Feuerstein, assistant professor of clinical medicine at Columbia University in New York and director of integrative medicine at Stamford Hospital in Connecticut.

“The majority of people do not understand that there is a significant difference in regulation between pharmaceuticals and supplements. The FDA classifies supplements the same way as food. So, if you eat a carrot or take a vitamin D pill, the FDA does not see a difference, even though you know what’s in a carrot and might not know what’s in the pill,” he said.

According to the FDA, manufacturers do not have to prove their supplements are safe or live up to their marketing claims before they hit store shelves. The agency relies on customer complaints and reports of “serious adverse events,” such as a hospitalization or death, to identify supplements that might be unsafe and potentially issue a recall.

Despite the report on adulterated products, both Feuerstein and Levitan agree that safe supplement use can play a valuable role in patients’ health. In fact, the most popular supplements among adults are not the ones marketed for weight loss, sexual enhancement, or muscle building — they’re vitamins and minerals. These kinds of supplements may be less likely to have hidden ingredients, as manufacturers are not trying to meet claims of effectiveness.

Avoiding supplements that make big claims, such as promising a certain amount of weight loss, can help keep you safe, said Levitan.

“Those claims are a warning sign. Things that sound too good to be true, typically are,” she said.

When you’re scanning the pharmacy shelves for a supplement, look for bottles with the “USP Verified Mark,” said Feuerstein. This seal indicates that the product has been voluntarily evaluated by the United States Pharmacopeia, which checks that the supplement does not contain dangerous levels of contaminants and is made from the ingredients listed on the label.

“The USP Verified Mark shows that you’re at least getting what you’re hoping to get in the product,” he said.

Finally, work with your doctor to determine the right kinds and quantities of supplements for your health needs. “Vitamins and supplements have to be taken in a thoughtful, safe, and medically appropriate way, which is different for each person. Supplements don’t have to be tainted to be dangerous. Even with safe products, you can overdo it,” said Levitan.

An investigation found that hidden additives may be contained in certain supplements, mainly in those for weight loss, muscle building, or sexual health.

Experts say there are steps people can take to protect themselves including looking for the “USP Verified Mark” and working with a doctor to figure out what, if any, supplements they need.