More Bad News About Dietary Supplements

Kenneth W. Lin, MD, MPH


November 05, 2018

Editorial Collaboration

Medscape &

Hello, everyone. I'm Dr Kenny Lin, a family physician at Georgetown University Medical Center in Washington, DC, and I blog at Common Sense Family Doctor.

In a survey[1] conducted last year by the Council for Responsible Nutrition, more than three quarters of US adults reported taking over-the-counter dietary supplements. The most popular supplements were multivitamins and minerals, which, though unproven to produce health benefits for most persons,[2] are likely harmless if taken in doses similar to the National Academy of Sciences' dietary reference intakes.[3] However, 39% of supplement users took herbals, 29% sports supplements, and 19% supplements for weight loss. These types of supplements worry me more because they frequently contain unapproved ingredients with a high potential for harm. For example, a recent analysis of US Food and Drug Administration (FDA) warnings issued to manufacturers of 776 supplements from 2007 to 2016 found that they contained prescription drugs such as sildenafil, sibutramine, steroids, and fluoxetine.[4]

It may surprise patients, and some health professionals, that the FDA's legal authority to oversee the supplement industry is far inferior to its power to regulate the pharmaceutical industry. Unlike new prescription drugs, supplements do not need to be submitted to the FDA for review of their efficacy and safety before being marketed and sold. So, in the words of a former FDA official,[5] manufacturers are "essentially using an honor system." Physicians can and should report suspected adverse events from supplements to the MedWatch program so that the FDA can initiate an investigation and enforcement actions, if appropriate.

In addition to voluntary recalls of adulterated supplements, another enforcement action available to the FDA is posting public notices about prohibited hazardous ingredients on its Health Fraud webpage.

Have these notices caused manufacturers to remove these ingredients from products? Unfortunately, a study published in JAMA Internal Medicine[6] suggested that the notices may have little or no effect. Researchers performed chemical analyses of samples of 12 weight loss, sports, and cognitive supplements purchased in 2014 and compared them with the same brands purchased in 2017. In the intervening years, the FDA issued notices regarding four sympathomimetic stimulants. Nonetheless, at least one of the stimulants was detected in nine of the supplements purchased in 2017. Equally concerning, one stimulant, 1,3-dimethylbutylamine, was not found in any of the supplements in 2014 but was detected in four of them in 2017. Although this was a small sample, there is no reason to think that it was unrepresentative.

What should primary care physicians do with this information? First, in addition to asking about prescribed and over-the-counter drugs, be sure to ask your patients if they take any vitamins, herbals, nutritional, sports, or weight-loss supplements. Second, counsel patients without a clear medical indication for a particular supplement that they are wasting their money and exposing themselves to harm from interactions with prescription drugs[7] and risky ingredients, including those already prohibited by the FDA. Third, notify the FDA when you believe that one of your patients has experienced a serious adverse effect from a supplement. Finally, as Dr Melissa Walton-Shirley suggested in a commentary on Medscape, advocate for your state medical society and national specialty organization to demand legislation to give the FDA the authority and resources to ensure the safety and quality of supplements before they go on the market, not only after consumers experience avoidable harm.

This has been Dr Kenny Lin for Medscape Family Medicine. Thank you for listening.

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