Using weight loss or sports supplements? Exercise caution

The dietary supplement market has boomed to an estimated $46 billion in the US. And it's expected to continue to expand. If you believe the ads, supplements can improve your memory, joint health, heart health, sexual function, and enhance your well-being in many more ways. But let's be clear: many dietary supplements — perhaps most — are completely unproven, and may do little to improve health or fight disease. Worse, as a recent study shows, some can actually harm you.

Why are dietary supplements so popular?

Here are a few reasons:

• They seem safe. Because you don't need a prescription to get them, many people assume they're at least as safe as aspirin or acetaminophen (Tylenol), and less likely than prescription drugs to cause side effects.
• They're promoted as "all natural." Such products may seem much safer than a drug that's synthesized by a pharmaceutical company.
• Testimonials and recommendations. Trusted celebrities and "real people" are endorsing these products and offering up testimonials about how great they are. (It's worth noting that many of these folks are being paid for their advertising work.)
• Recommendations from friends and family. They may make it seem like not taking a supplement is endangering your health.
• Lack of evidence that a supplement works doesn't matter to many people. The argument is often made that lack of evidence doesn't mean something doesn't work; it might just mean the right study hasn't been done yet.
• If a supplement was harmful, wouldn't it be banned? Surely the FDA or another regulating body would know if a supplement was causing harm and make sure it was banned.

These may seem like convincing arguments. But, as a recent study demonstrates, maybe they aren't convincing enough.

The story of deterenol

A 2021 study in the medical journal Clinical Toxicology analyzed supplements intended to encourage weight loss or improve sports performance. The researchers identified 17 brands of supplements available in the US that listed deterenol as an ingredient and purchased these online.

Why deterenol? Despite the fact that it's never been approved for human use in the US, this potentially dangerous stimulant has been found previously in over-the-counter dietary supplements marketed for weight loss or improved sports performance. It can cause agitation, palpitations, and even cardiac arrest.

The FDA banned the use of deterenol in dietary supplements in 2004. The World Anti-Doping Agency has also banned its use due to safety concerns.

In their analysis, the researchers found deterenol in varying doses. They also found eight other prohibited stimulants. Two brands contained a combination of four different banned stimulants.

What's the big deal?

First, anyone using these supplements could unknowingly be taking a major health risk. There's also the possibility of getting disqualified from athletic competition.

And the combinations of ingredients found in these products could interact with each other, or with other medications you take. The study authors note that "…these cocktails of stimulants have never been tested in humans and their safety is unknown."

Unfortunately, this is not an isolated example: supplements to enhance male sexual performance or to lose weight have been recalled because they contained medications that weren't disclosed to users. Of course, the "extra" ingredients might make tainted products more effective than their competitors, which might improve sales. And these examples are likely just the tip of the iceberg: there may be many more tainted supplements out there that we don't know about.

What about the FDA?

The FDA regulates dietary supplements but, as noted on its website, the FDA isn't authorized to review these products for safety and effectiveness before they are sold. FDA actions largely occur after a product is on the market, such as a recall if a product proves to be unsafe, or marketing claims are false or misleading.

Clearly, keeping close track of every dietary supplement on the market is an enormous job, and well beyond what the FDA can do. We simply can't rely solely on the FDA to keep us safe from tainted supplements.

What's a supplement lover to do?

If you're taking a supplement, think about why you're taking it and whether the balance of risks and benefits is clearly in your favor. Check with your doctor. Do some reading about what you're taking, but pick your information sources carefully. Stick with trusted sites such as the CDC, the NIH, or academic medical centers. Look for products that are verified by independent testing companies such as ConsumerLab, NSF International, or US Pharmacopeia (USP).

And consider stopping supplements that haven't been recommended by your doctor, aren't doing what you expected them to do (such as reducing joint pain), or if you aren't sure why you're taking them. Apply a grain of salt (or two) to online anecdotes, "I-have-a-friend" stories, and celebrity testimonials. Better yet, tune them out entirely.

The bottom line

Dietary supplements may be less safe and effective than you thought. Regulation of dietary supplements is far less stringent than prescription medications, and there are too many supplements available from too many sources to police them all well.

While most supplements are probably harmless, many may be doing little or nothing to improve health. The word that keeps coming to mind as I think about dietary supplements is this: beware. Ask yourself if you really know what's in the bottle, and whether you truly need it. In general, it's best to take only what you actually need. That's true for prescription medicines. And it's also true for supplements.

Follow me on Twitter @RobShmerling