乌鸦传媒

Patients who think they're taking a botanical extract from the bark of a west African evergreen tree may actually be getting a pharmaceutical-grade product -- as well as the side effects that come with it, researchers said.

In an analysis of nearly 50 of the most popular brands of yohimbe supplements, about 40% didn't contain other alkaloids that would be commonly found in yohimbe extract, suggesting a highly processed form of the active ingredient yohimbine, according to , of the Cambridge Health Alliance in Massachusetts, and colleagues.

"If you have yohimbine that's highly refined to higher-than-prescription doses, you're selling a drug," Cohen told 乌鸦传媒. "You shouldn't be able to make a pharmaceutical drug -- even if it is found in a plant -- and put it in supplements and sell it over-the-counter."

Cohen, who is earning a reputation as a critic of the way the U.S. handles its $36 billion supplement industry, and his colleagues sold at seven of the top retailers in the U.S. in a special edition of the journal .

He said the findings add to the mounting evidence that the Dietary Supplement and Health Education Act (DSHEA) is too lax and offers little consumer protection.

"Manufacturers are given free rein to do anything they want in terms of processing their product," Cohen said. "What consumers think is a simple botanical extract is closer to a pharmaceutical ingredient. The law allows this mischief."

, associate dean of public health at Johns Hopkins and a former FDA official, who wasn't involved in the study, said the findings "reflect a serious problem in the market for dietary supplements," with many products being spiked with pharmaceutical ingredients.

"There's a growing awareness, even inside industry, that more needs to be done to assure safety," Sharfstein said.

Extract from the bark of the evergreen tree common to west Africa has long been used as an aphrodisiac or to enhance sexual performance. Its main active ingredient is yohimbine, one of many alkaloids in the plant, but only 1% of yohimbe bark is active yohimbine, Cohen said, which is why supplement makers are tempted to concentrate the product.

Prescription yohimbine was available in the U.S. for many years, but its popularity has fallen off -- possibly due to the widespread uptake of PDE5 inhibitors like sildenafil (Viagra), he said. It hasn't been part of the Physicians' Desk Reference since 2005.

Studies of pharmaceutical-grade yohimbine have shown some efficacy in sexual dysfunction, but at the cost of side effects such as panic attacks, hypertension, and headaches. The NIH Office of Dietary Supplements says studies have shown "" and that the supplement "can be dangerous," causing cardiac failure and death at doses of 200 mg or higher.

Such findings have led some countries, including the U.K., the Netherlands, Canada, and Australia, to ban yohimbe supplements.

But yohimbe supplements are widely available in the U.S., with some 550 products on the market -- and they're popular, too, ranking in the 30 top-selling botanical ingredients, Cohen said.

He became interested in yohimbe after seeing unusual symptoms in patients. When one came in flushed and with chest discomfort, Cohen suspected supplements spiked with Viagra-like drugs, which can cause flushing.

However, when Cohen had the patient's supplements analyzed, there was no rogue Viagra, just "a lot of yohimbine," he said.

So he and his colleagues decided to take a closer look, and sampled 49 brands of supplements that claimed to contain yohimbe or yohimbine that were sold in seven popular stores: GNC, Vitamin Shoppe, Walgreens, Walmart, CVS, Rite Aid, and Whole Foods.

They sent the products to the University of Mississippi's National Center for Natural Products Research for analysis via ultra high-performance liquid chromatography coupled to photodiode and quadrupole time-of-flight mass spectrometry detectors.

And they didn't only look for yohimbine: they checked for two of the other alkaloids that commonly occur in the plant as well: rauwolscine and corynathine. If the supplement did indeed contain only botanical extract, those compounds should be present.

They found that the actual dose of yohimbine in each product ranged all the way from 0 to 12 mg -- although the dosing tended to skew toward higher concentrations than labeled, Cohen said -- and that latter figure is higher than the 5 mg or 10 mg doses that prescription yohimbine was available in.

More than a third (39%) of the supplements didn't contain the two other alkaloids, suggesting that the yohimbine was either synthetic, or heavily processed.

"They should have been there if this were simple extract from a tree," Cohen said.

Some of the brands specifically put the pharmaceutical-grade name "yohimbine hydrochloride," or "yohimbine HCL," on their labels. Among all 16 brands that did so, none of them contained the two other alkaloids. On the other hand, 88% of the brands that didn't put this more technical name on the label had at least one of the two other alkaloids.

When it came to labeling active ingredients and adverse events, only 22% of products actually listed the quantity of yohimbine on the label. Even when they did, there was a good chance of mislabeling, with doses often running far higher than what was stated, Cohen said.

Although the majority of producers put information about side effects on their labels, about one in five still did not. And overall, only two brands accurately labeled both the quantity of yohimbine and adverse effects. (These, however, did not contain the other two alkaloids, suggesting they were highly processed.)

The researchers acknowledged that their study was limited because they only analyzed one sample from each brand of supplement, but Cohen said this kind of practice wouldn't be unusual in a system that doesn't require companies to report how much active ingredient is in the product or what its side effects might be.

Cohen has been aggressively taking on the supplement industry, and Science recently dubbed him ""

Last spring, his study that found a in several over-the-counter products made headlines and subsequently led to the . As is the case with yohimbine, BMPEA is not allowed on the market in several countries but is not banned in the U.S.

Although some say reforming DSHEA and beefing up regulation of supplements -- particularly if it should fall squarely on the shoulders of the overtaxed FDA -- is futile, Cohen doesn't seem deterred. He lists several steps that could go a long way, including requirements to list all ingredients and adverse effects on product labels, mandatory registration of all products with the FDA, and standardizing supplement recipes so there's less variation in composition.

Even the simple step of cutting the "structure function claims" that are allowed to appear on supplement labeling could have a huge impact, he said. These are the claims that the product "supports" or "boosts" all types of health from sexual health to immune function.

"If you couldn't sell a product that 'improves sex life' and you just had to sell 'yohimbe, ...'" Cohen said, "you don't have perverse incentives to try to create something from a botanical extract that looks more like a pharmaceutical."

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