“Some non-vitamin supplements are marketed heavily in the absence of reliable evidence of efficacy or safety and may interact with prescription drugs. Moreover, some people may delay beginning proven therapies because they are relying on supplements. And some of these products are costly,” says Dr. David Eisenberg, adjunct associate professor at the Harvard T.H. Chan School of Public Health.
The supplements used in government-funded clinical studies are analyzed for purity and standardized for dose. Supplement manufacturers are required to perform such analyses and to supply the results to the FDA. Yet, according to a report aired in January 2016 by PBS’s investigative series Frontline, few of the thousands of supplement manufacturers do so, and the FDA lacks the staff and resources to analyze supplements or to compel manufacturers to comply.
As a result, the contents of a supplement capsule may not be what’s described on the label. Canadian researchers who analyzed a random sample of 44 products from 12 manufacturers reported in 2013 that 60% of the products contained substances not listed on the labels, some of which were potentially harmful contaminants. And a 2015 investigation by the New York attorney general determined that only 21% of random samples of popular house-brands supplements purchased from GNC, Target, Walgreens, and Walmart contained the ingredients in the concentrations listed on the labels. Some contained no trace of the advertised active ingredient, and others consisted primarily of “fillers,” including wheat and soy, which may trigger allergic reactions in some people. Other investigations have uncovered supplements adulterated with steroid hormones.
When it comes to dietary supplements, the ancient warning “buyer beware!” is more relevant than ever.