Looking to enhance sexual performance, cure erectile dysfunction, lose weight, or improve your athletic ability? Dietary supplements listing the botanical ingredient yohimbe claim to provide a “natural” quick fix for all those and more. The ingredient, extracted from the bark of the African Pausinystalia yohimbe tree, is now found in more than 550 supplements.

But taking dietary supplements with yohimbe is risky, according to a new study published online in the journal Drug Testing and Analysis. Yohimbe has been linked to fatigue, stomach disorders, and even paralysis and death. Yet labels often don't mention those risks, the study found.

Worse, in many cases the products—bought at  CVS, Walgreens, GNC, Rite Aid, Vitamin Shoppe, Walmart, and Whole Foods—contained much more (and sometimes less) of the ingredient than they claimed. Most troubling, the study found that many products contained potentially dangerous levels of a yohimbe-derived drug.

“The law regulating supplements is so weak that it does not even require manufacturers to declare what’s actually in supplements, even when supplements contain the equivalent of powerful, prescription-strength drugs," says Harvard Medical School internist and dietary supplement expert Pieter Cohen, M.D., who conducted the study. "Consumers are exposed to potent drugs without even knowing the dose or safety of what they’re taking,” he says.

A Dangerous Herb

Yohimbe has traditionally been viewed as an aphrodisiac, and before Viagra was approved, a medication derived from the yohimbe tree was often prescribed for erectile dysfunction.

While that drug is now rarely used, yohimbe supplements (supposedly containing just the natural extract) are still popular—despite a long history of risks. Supplements containing it have been linked to more than 130 hospitalizations between 2000 and 2006 in California alone, for example. And in 2013, U.S. Poison Control Centers logged 227 cases related to yohimbe supplements—99 of which required treatment in a health care facility. Concerns about yohimbe have prompted Australia, Canada, the Netherlands, the U.K., and other countries to ban supplements that contain it.

The U.S. Food and Drug Administration, on the other hand, still allows yohimbe  supplements to be sold. And because the FDA doesn’t regulate botanical supplements as rigorously as it does prescription and over-the-counter drugs, it’s hard to know whether those dietary supplements even contain what they claim. “Our study was an attempt to find out,” Cohen says.

What’s Really in the Pills

Cohen and his colleagues from the National Center for Natural Products Research at the University of Mississippi tested 49 supplements that claimed to contain the tree bark extract. One sample didn’t contain any detectable yohimbe, while another exceeded the maximum dosage of the pharmaceutical yohimbe-derived medication that doctors can prescribe by about 21 percent.

He also looked at the labels to see what they claimed. Three quarters of them didn’t list how much yohimbe they contained. Of the 25 percent that did, only three  were labeled accurately. The others ranged from 75 percent less than the listed amount to 50 percent more.

Most worrisome, Cohen found that many of the products likely contained a pharmaceutical grade version of the ingredient. “Incredibly, we found pharmaceutical dosages of yohimbine in more than 40 percent of the products,” Cohen says. “These products contain the equivalent of a drug. People are going to the store to purchase a natural remedy, but it turns out they’re actually buying drugs.”  

“Because of the way supplements are regulated in this country, dangerous products like yohimbe are legally sold to unsuspecting consumers,” says Marvin M. Lipman, M.D., Consumer Reports’ chief medical adviser. “Yohimbe supplements should be taken off the market, and the law for dietary supplements should be changed, so consumers can be confident that the products do what they claim and contain what’s listed on the label,” he says.

Consumer Reports' Take

Be wary of all dietary supplements, especially those marketed for male enhancement, bodybuilding, and weight loss. Research suggests those products frequently contain adulterants—including dangerous prescription or experimental drugs.