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There can be many reasons why someone may choose to buy a dietary supplement. Some prefer supplements over prescription drugs, believing them to be more “natural” and possibly more gentle than prescription drugs. While there is a lack of good evidence showing most dietary supplements have any meaningful benefit, there is one effective way to make a supplement “work”: Add an active ingredient. Juicing up a supplement with actual prescription drugs isn’t uncommon – it happens routinely, and there is little that the Food and Drug Administration can really do about it. While supplements are often packaged like pharmaceuticals, and may be sold alongside over-the-counter drugs, anything considered a dietary supplement is subject to completely different regulatory standards than is in place for prescription drugs. And that’s created a marketplace where consumers are ill-served and may even be at risk of harming themselves.

Supplements are not drugs (according to regulators)

It’s been covered in depth before, but is worth repeating, that the Dietary Supplement Health and Education Act of 1994 ( DSHEA ) was an amendment to the U.S. Federal Food, Drug and Cosmetic Act that established the American regulatory framework for dietary supplements. It effectively excludes manufacturers of these products from virtually all regulations that are in place for prescription and over-the-counter drugs, and puts the requirement to demonstrate harm on the FDA, rather than the onus on the manufacturer to show a product is safe and effective. The goal was to eliminate barriers to sale, and it worked: Within four years of the DSHEA , supplement sales grew from $4 billion to $12 billion. Today, dietary supplements are a $35 billion industry.

Because there is no pre-market or post-market product testing in place, the FDA relies on other forms of monitoring in an attempt to ensure that supplements are safe. This includes collecting adverse event reports and consumer complaints, inspecting manufacturing facilities, and monitoring imported ingredients. In exceptional circumstances, the FDA can take supplements off the market by issuing a recall.

Despite the perception that supplements are safe, natural, and effective, they continue to cause a significant amount of harm, associated with 23,000 emergency department visits and 2,000 hospitalizations per year. This number may in fact be an underestimate, as assessing causality is challenging, and erroneous perceptions about supplements may mean fewer people even suspect a supplement of causing harm.

The FDA maintains a Tainted Products Marketed as Dietary Supplements database, which was the data set used for a recent study I will be discussing below. Adulterated dietary supplements are particularly problematic for consumers, because it is impossible to safely take a prescription drug if you don’t know you’re taking it at all. And if you have medical conditions, or take other prescription drugs, your risk of harm from adulterated supplements is even greater.

Counting the adulterated supplements

The study was a straightforward analysis of FDA data. Jenna Tucker and colleagues examined adulterated supplements, defined as supplements containing unapproved ingredients (e.g., prescription drugs). The paper is entitled “Unapproved Pharmaceutical Ingredients Included in Dietary Supplements Associated With US Food and Drug Administration Warnings,” published in JAMA Network Open last week. The objective was to summarize trends observed in adulterated supplements associated with an FDA warning, between 2007 and 2016. 776 supplements were in the data set, and the majority of them were products marketed for sexual enhancement (46%), weight loss (41%), and muscle building (12%), with only 2% of products marketed for other purposes. (See table)

While most products had only one unlabelled prescription drug as an adulterant, just over 20% contained two or more. Two products (one marketed for arthritis and one for sexual enhancement) contained six different unlabelled drugs.

Among the warnings, 96% of products were associated with a single warning. Amazingly, 28 products were found to repeatedly contain adulterants, with 19 (67%) of these product being laced with DIFFERENT prescription drugs the second or third time around.

Just under half of the products in this sample were associated with a voluntary recall from the manufacturer. Surprisingly, in 44% of cases, there was a public notification only, and no recall.

Key highlights of the findings

Supplements for sexual enhancement: Among the adulterants, sildanafil, (the active ingredient in Viagra) was the most common, with 81% of the sexual enhancement supplements containing it or a close chemical analogue.

Supplements for weight loss: The most common adulterant in weight loss supplements was the weight loss drug silbutramine (or an analogue) along with the laxative phenolphthalein, both of which have been removed from the US market. Silbutramine was found in 85% of weight loss products in the dataset, and phenolphthalein was in 24% of these products. Some weight loss supplements were also found to contain the prescription drug fluoxetine (Prozac).

Supplements for muscle building: 73 of the 92 supplements had undeclared anabolic steroids (or steroid-like analogues). In what could be described as a form of honesty in supplement advertising, nine products did disclose that the supplement actually contained anabolic steroids. Ten products disclosed that they contained a class of anti-cancer drugs call aromatase inhibitors, which are used to block estrogen.

Other supplements: While marketed for a variety of conditions including pain, cancer, sleep issues, gout and prostate health, half of the products (7 of 14) contained diclofenac (an anti-inflammatory drug) and five contained dexamethasone (a steroid).

What does it mean for me, the consumer?

When supplements are tainted with prescription drugs, they’re no longer dietary supplements – they’re unlabelled drugs. Consumers should be entitled to dietary supplements that at minimum, honestly and accurately describe what’s inside the bottle (meaning not just lacking adulterants, but including the purported active ingredient). This analysis show that unapproved drugs are regularly sold in the United States as dietary supplements, and there are no signs that regulation will change this fact. However, it is possible to greatly reduce your risk of purchasing adulterated supplements. If you stay away from erectile dysfunction supplements, weight loss supplements, and muscle building/bodybuilder supplements, there’s a much better chance that you won’t be getting any prescription drug surprises in your dietary supplement. Until there is better, more effective regulation of dietary supplements, consumers will continue to put their health at risk with each supplement they consume.