The Safety of Weight-Loss Supplements 

Only 2 out of 12 supplement companies were found to have weight-loss products that were even accurately labeled.

According to a national survey, one-third of adults who have made serious attempts at weight loss have tried using dietary supplements, for which Americans spend billions of dollars every year. Most people mistakenly thought that over-the-counter appetite suppressants, herbal products, and weight-loss supplements had to be approved for safety by a governmental agency, like the U.S. Food and Drug Administration (FDA), before being sold to the public or at least include some kind of warning on the label about potential side effects. Nearly half even thought they had to demonstrate some sort of effectiveness. None of that is true.

As I discuss in my video Friday Favorites: Are Weight Loss Supplements Safe and Effective?, the “FDA has estimated that dietary supplements cause 50,000 adverse events annually,” most commonly liver and kidney damage. Of course, prescription drugs don’t just have adverse effects; they kill more than 100,000 Americans every year. But, you at least notionally have the opportunity to parse out the risks versus benefits of prescription drugs, thanks to testing and monitoring requirements typically involving thousands of individuals.

When the manufacturer of Metabolife 356, a supplement containing ephedrine, had it tested on 35 people, only minor side effects were found, such as dry mouth, headache, and insomnia. However, once unleashed on a broad population, nearly 15,000 adverse effects were reported, including heart attacks, strokes, seizures, and deaths, before it was pulled from the market.

Given the lack of government oversight, there is no guarantee that what’s on the label is even in the bottle, as you can see in the graph below and at 1:55 in my video. FDA inspectors have found that 70 percent of supplement manufacturers violated so-called Good Manufacturing Practices, which are considered the minimum quality standards. This includes things like basic sanitation and ingredient identification. Not 7 percent in violation, but 70 percent.

DNA testing of herbal supplements across North America found that most could not be authenticated. In a significant percentage of the supplements tested, the main labeled ingredient was missing completely and substituted with something else. For example, a so-called St. John’s wort supplement contained nothing but senna, a laxative that can cause anal blistering. Only 2 out of 12 supplement companies had products that were accurately labeled.

This problem isn’t limited to fly-by-night phonies in some dark corner of the internet either. The New York State Attorney General commissioned DNA testing of 78 bottles of commercial herbal supplements sold by Walgreens, Walmart, Target, and GNC “and found that four out of five…did not contain any of the herbs on their labels.” Instead, the capsules “often contained little more than cheap fillers like powdered rice, asparagus and houseplants…”

What about weight-loss medications? See Are Weight Loss Pills Safe? and Are Weight Loss Pills Effective?. Also, see related posts below.

Take a deep dive into the best way to lose weight with my book How Not to Diet

Key Takeaways

  • A national survey indicates that one-third of adults making serious weight-loss attempts have used dietary supplements, with most falsely believing that these products are approved for safety by agencies like the FDA or include a warning label about side effects, and many think they must demonstrate effectiveness. In reality, none of these assumptions is accurate.

  • The FDA estimates that dietary supplements cause around 50,000 adverse events a year, most commonly liver and kidney damage. While prescription drugs have adverse effects and may even kill users, they undergo testing and monitoring involving thousands of individuals, allowing for better risk-benefit analysis. 

  • Metabolife 356, a supplement containing ephedrine, was found to have only minor side effects when tested on 35 people, but when it was widely used, nearly 15,000 adverse effects were reported, including heart attacks, strokes, seizures, and even deaths, before it was pulled from the market. 

  • Due to the limited government oversight of dietary supplements, there is no guarantee that the ingredients listed on the label are actually present in the product. FDA inspectors found that 70 percent of supplement manufacturers violate Good Manufacturing Practices, which include basic standards like sanitation and ingredient identification. 

  • DNA testing of North American herbal supplements found that most could not be authenticated. The primary labeled ingredient was missing and substituted with something else in 68 percent of the supplements tested, for example. Only 2 of 12 supplement companies had accurately labeled products. 

  • DNA testing commissioned by the New York State Attorney General on commercial herbal supplements from major retailers (Walgreens, Walmart, Target, and GNC) found that four out of five didn’t have any of the listed herbs. Instead, they “often contained” inexpensive fillers, like powdered rice and houseplants.


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