Instant coffee sold online for two years was found to contain an ingredient chemically similar to Viagra.
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On the back of virtually any bottle of supplements, beneath the bold lettering claiming to list the ingredients, are two words that strike fear into the heart of Pieter Cohen, a Harvard Medical School assistant professor
: "proprietary blend."

Under the protective umbrella of these words, Cohen said, a supplement maker does not have to list the details of what's in the product.

That is what most likely happened with a type of instant coffee — sold by the Texas-based vendor Bestherbs Coffee LLC — that the Food and Drug Administration recently found to contain an ingredient chemically similar to Viagra.

"Proprietary blend" is essentially a loophole that "allows companies to put in ingredients without telling us the amounts," Cohen said during a panel discussion
organized by the Harvard T.H. Chan School of Public Health. "And those tend to be the higher-risk product."

The coffee, sold under the name New of Kopi Jantan Tradisional Natural Herbs Coffee, was available online for nearly two years, between 2014 and 2016. But last week, the FDA announced that the company was voluntarily recalling the product
after testing revealed it contained undeclared ingredients. Desmethyl carbodenafil, in particular, raised alarms, since it's chemically similar to sildenafil, the active ingredient in the popular erectile-dysfunction drug viagra online.

Bestherbs' packaging merely says the instant coffee has "natural herbs."

The FDA has recently overseen the recall of two other similar coffee products: Stiff Bull Herbal Coffee and Caverlo Natural Herbal Coffee. The vendor of each claimed its coffee included an ingredient called tongkat ali, or "longjack," that's derived from the root of a Malaysian tree.

The ingredient is increasingly being used in supplements claiming to have "male enhancement" properties. While some limited evidence
suggests that taking a specific tongkat ali supplement can improve the quality and concentration of sperm in infertile men, there is little evidence to support its use
for erectile dysfunction, athletic performance, or low testosterone.

The ingredient can also have dangerous side effects, which is why it's important for people to know what they are consuming.