Dietary supplements include a wide range of products including vitamins, minerals, botanicals and probiotics, protein powders, and fish oils. Over the past two decades, a steady stream of high-quality studies evaluating supplements have been published. Mostly they have showed little to no benefit from supplements, whereas evidence of harm from supplements has been mounting. One might reasonably conclude that based on studies showing no benefit and potential harm from supplements that their use would be declining, however recent studies on the use of supplements show that their use has remained steady from the late 1990s to 2012. A national survey found that 52 percent of the US population used supplements and that number has remained constant over the last 20 to 25 years.
To put the continued use of products that have little to no benefit and may be harmful into perspective, it helps to look at the regulatory changes that have happened. In 1994 Congress passed the Dietary Supplement Health and Education Act (DSHEA). Under this law, all supplements are presumed to be safe until the FDA detects evidence of harm, which usually occurs after consumers have been extensively exposed to the product. This led to a rapid expansion of the supplement market, from 4000 products in 1994 to 55,000 in 2012. By 2012 dietary supplements had grown to be a $32 billion industry.
Examples of published studies showing no benefits of supplements include multivitamins to prevent cancer and heart disease, echinacea to treat the common cold, St. John’s wort for depression and vitamin E for prostate cancer prevention. In addition, in the late 1990s and early 2000s, supplements containing ephedra were linked to heart attacks, seizures, strokes, and sudden deaths (ephedra is now banned in supplements). Other studies showed that smokers taking long-term beta-carotene supplements had increased risk of developing lung cancer. It should be noted however that supplements can be used to treat vitamin and mineral deficiencies and combination products can be useful in delaying progression of age-related macular degeneration. But the use and overuse of products to “improve” or “maintain” health has been proven to be mostly worthless.
So why would people continue to pay for and use products that are either useless or harmful? Many consumers may not be aware of the negative studies or may not have faith in the scientific process. Plus the negative findings may be counterintuitive – people have always been told that vitamins and minerals are good for you. Also DSHEA permits the promotion of supplements using “structure/function claims.” For example claims such as “supplement X preserves heart function” or “supplement Y maintains mental alertness” are permitted without proof of benefit. Such claims must have a disclaimer like “these statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any illness.” But who listens to disclaimers? Ginkgo biloba continues to be sold “to support mental sharpness” despite a large, high-quality study showing no benefit.
If you take any supplements be sure your doctor is aware of their use. Plus always ask your doctor if a supplement may be useful before taking it. Remember that some supplements may interact with prescription medications or may adversely affect your health.
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