Your dietary supplement could be tainted by prescription drugs, study finds


Editor’s Note: The following is an overview of the research provided by study author C. Michael White, professor of pharmaceutical practice at the University of Connecticut.

(The Conversation) — Many over-the-counter dietary supplements — especially those used for sexual enhancement and weight loss — are tainted with undisclosed pharmaceutical ingredients. This is the main finding of my review recently published in the Journal of Clinical Pharmacology.

My assessment of the Food and Drug Administration’s Health Fraud Products Database found 1,068 unique dietary supplement products marketed between 2007 and 2021 that contained active ingredients found in prescription drugs or deemed too dangerous for use in humans. Of the contaminated dietary supplements my study identified, 54% were for sexual dysfunction and 35% for weight loss. While many such products are removed from the market once detected by the FDA, other contaminated dietary supplements may end up on the market in their place.

why is it important

Dietary supplements are used by 58% of American adults. And according to recent surveys by the Council for Responsible Nutrition, American consumers have a moderate level of confidence in the quality and safety of dietary supplements. However, my study suggests that this confidence is misplaced, as many dietary supplements contain unlabeled synthetic active ingredients.

So what are these hidden substances and why are they important?

The active ingredient sibutramine, which the FDA recommended removing from the US market in 2010 after research showed it increased the risk of heart attacks and strokes, is hiding in many contaminated weight loss supplements. And phenolphthalein, also commonly found in diet supplements in the FDA database, was removed from over-the-counter laxative products in 1999 when the FDA reclassified it as “not generally recognized as safe and effective.” The FDA warning came after studies showed the ingredient can damage people’s DNA and increase cancer risk.

My study also identified the presence of ingredients approved only for use in prescription drugs. These include sildenafil and tadalafil, which are used in FDA-approved erectile dysfunction drugs like Viagra and Cialis. Such inadvertent uses can be dangerous, as the active ingredients of these drugs carry risks such as loss of vision or priapism, or prolonged erection of the penis. My study also documented frequent cases in which more than one active ingredient found in erectile dysfunction drugs were combined in a way that had never been studied for safety.

Another reason hidden active ingredients are problematic is that they pose a risk of serious drug interactions. When the active ingredients found in erectile dysfunction drugs are used with blood pressure or prostate medications such as nitrates and alpha-1 blockers, life-threatening drops in blood pressure can occur.

Similarly, two of the dietary supplements identified in my study contained flibanserin, the active ingredient in the prescription drug Addyi, used to treat female sexual dysfunction. Flibanserin is generally safe, but can significantly lower blood pressure if used with alcohol.

Pharmacists check for these types of drug interactions before dispensing prescription drugs. However, if undisclosed ingredients are hidden in dietary supplements, it is impossible to prevent adverse drug interactions.

What is not yet known

Manufacturers of dietary supplements do not provide evidence of good manufacturing practices to the FDA before selling them in the United States, and these manufacturers may change their products without notice. The FDA must prove a dietary supplement product is unsafe before it can take action, but this is difficult to enforce when there are more than 29,000 dietary supplement products sold in the United States.

FDA evaluations are laborious and expensive because these evaluations also aim to detect other dietary supplement problems such as the presence of heavy metals or bacterial or fungal contamination. The agency’s evaluation process for these supplements is also deeply underfunded. The FDA alerts consumers to newly detected contaminated dietary supplements through its Health Fraudulent Products Database while attempting to remove these products from the market.

If the product you plan to use is on this list, avoid it. However, if your product is not included in the database, it may simply mean that it has not yet been reviewed.

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