Recent findings confirm what the New Jersey Poison Control Center has known for some time: There's much more than meets the eye when it comes to dietary supplements, and consumers must be cautious when ingesting a substance they can simply grab off the pharmacy or supermarket shelves.

"Even what you read on the bottle of a dietary supplement just may not be the truth," said Dr. Diane Calello, medical director of the Rutgers-based Poison Control Center. "This is an ongoing problem."

In an analysis of U.S. Food and Drug Administration data, published in the Journal of the American Medical Association, it was found that nearly 800 dietary supplements sold over the counter from 2007 through 2016 contained unapproved pharmaceutical ingredients, including prescription medicines.

The flagged supplements are essentially unapproved drugs, the study authors wrote. In 97 percent of the cases, the unapproved ingredients wee not listed on the product's label.

The FDA does not assess the safety of supplements prior to them hitting the market, the study noted, but the agency is tasked with spotting and removing adulterated supplements from the marketplace.

The study analyzed the FDA's "tainted products" database. Sexual enhancement supplements were found to the be most adulterated, followed by weight-loss products and supplements for muscle building.

"We know that people who take dietary supplements do sometimes have a bad health event as a result," Calello said. "And we do get calls about this."

These calls typically don't come directly from a consumer, she said, but nurses and doctors would call the Center to get information on a supplement that a patient presenting with kidney problems or high blood pressure, for example, is currently taking.

"Many times we do find that the supplement, which may not have a labeled ingredient that's bad for a patient, contains an unlabeled ingredient that's bad for the patient," she said.

If thinking about taking a supplement for any number of reasons, Calello said, talk to your doctor to determine the best and safest option.