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Studies show little benefit in supplements

By Jane Brody
Nov. 23, 2016 at 9:14 p.m.

A woman walks past a GNC store on Feb. 3, 2015, in New York.

NEW YORK — Americans spend more than $30 billion a year on dietary supplements — vitamins, minerals and herbal products, among others — many of which are unnecessary or of doubtful benefit to those taking them. That comes to about $100 a year for every man, woman and child for substances that often are of questionable value.

The passage of the Dietary Supplement Health and Education Act of 1994 opened the floodgates to an industry that can bring these products to market without submitting any evidence to the Food and Drug Administration that they are safe and effective in people. The law allows the products to be promoted as "supporting" the health of various parts of the body if no claim is made that they can prevent, treat or cure any ailment. The wording appears not to stop many people from assuming that "support" translates to a proven benefit.

After 1994, sales of a very wide range of supplements skyrocketed, and because the law allowed it, many continued to be sold even after high-quality research showed they were no better than a placebo at supporting health. The government can halt sales of an individual product only after it is on the market and shown to be mislabeled or dangerous.

The latest study, published in October in JAMA, found that overall use of dietary supplements by adults in this country has remained stable from 1999 through 2012, although some supplements have fallen out of favor while the use of others has increased.

The study, directed by Elizabeth D. Kantor, an epidemiologist at Memorial Sloan Kettering Cancer Center in New York, revealed that 52 percent of adults used one or more supplements in 2012. If anything was surprising about the findings, it was that the number of supplement users was not even higher given the products' robust promotion in paid advertisements and testimonials on the internet.

The findings were derived from in-home interviews with 37,958 adults in the National Health and Nutrition Examination Survey. The survey is conducted every two years among a nationally representative sample of Americans living at home.

In an accompanying editorial titled "The Supplement Paradox: Negligible Benefits, Robust Consumption" accompanying the new report, Dr. Pieter A. Cohen, of Cambridge Health Alliance and Somerville Hospital Primary Care in Massachusetts, pointed out that "supplements are essential to treat vitamin and mineral deficiencies" and that certain combinations of nutrients can help some medical conditions, like age-related macular degeneration. He added, however, "for the majority of adults, supplements likely provide little, if any, benefit."

Among the changes found in the new study: multivitamin/mineral use declined to 31 percent from 37 percent, "and the rates of vitamin C, vitamin E and selenium use decreased, perhaps in response to research findings showing no benefit," Cohen wrote. Sometimes people do act sensibly when faced with solid evidence.

However, he added, "other products continued to be used at the same rate despite major studies demonstrating no benefit over placebo." Thus, the use of glucosamine-chondroitin to relieve arthritic pain remained unaffected by the negative results in 2006 of the Glucosamine/Chondroitin Arthritis Intervention Trial and several follow-up analyses.

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