Dietary Supplements: When Will They Ever Learn?

When we wrote about problems with dietary supplements in 2002, we concluded by saying that physicians should tell their patients that we really don’t know what’s in them. An article that recently appeared in JAMA Network Open1 tells us what’s in some of them, and it’s not good.

The data in the new report comes from the FDA’s Tainted Supplements database, which relies on postmarketing surveillance and is undoubtedly incomplete. A total of 776 dietary supplements, produced by 146 different companies, were identified as containing unlisted pharmaceutical ingredients. Most of these products were marketed for sexual enhancement, weight loss or muscle building, and most commonly contained sildenafil (Viagra, and generics), sibutramine (Meridia; removed from the US market in 2010), and anabolic steroids. Other unlisted ingredients included diclofenac, furosemide, phenytoin, ephedrine, and dexamethasone, all in unknown concentrations. The potential for toxicity, overdose, and drug interactions is clear.

Given how unlikely it is that the US Congress will ever require premarketing FDA approval of dietary supplements,2 the obligation to protect our patients from these unproven, potentially dangerous products falls on us. Some supplement manufacturers voluntarily submit their products to USP or other independent institutions for verification. USP, for instance, will allow its seal to be displayed on the labels of products it verifies are made using Good Manufacturing Practices and contain the labeled ingredients in the correct doses without unlabeled additives or harmful levels of contaminants. A USP seal does not indicate that a product has any medical benefit, but it’s a good indication that what’s on the label is what’s in the container.

  1. J Tucker et al. Unapproved pharmaceutical ingredients included in dietary supplements associated with US Food and Drug Administration warnings. JAMA Network Open 2018; 1:e183337.
  2. M Incze and MH Katz. Regulating the dietary supplement industry. JAMA Intern Med 2018 October 22 (epub).

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