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About 52% of Americans take dietary supplements

Research over the past decade has showed that many don't help health

CNN  — 

The majority of American adults use dietary supplements. That number has remained steady for about the past decade, according to a new study, despite an increase in the number of studies that show that many supplements, with some exceptions, produce mixed results at best or, at worst, have no real health benefits at all.

The study appears in the latest edition of the Journal of the American Medical Association.

Americans spent about $34.9 billion on supplements in 2013 alone, according to National Institutes of Health research. There were an estimated 50,000 supplement products to choose from in the 2012 market.

Among American adults, 52% had taken a dietary supplements in the past 30 days, according to data from 2011-12 surveys. That’s about the same as it has been since 1999-2000. There had been an increase in the number of people taking them in the two decades before.

“In 2007-2010, only 23% of all supplement products were used at the recommendation of a healthcare provider,” the study said.

Though the current numbers haven’t changed, what has changed is the amount of research highlighting how little some supplements help.

The National Institutes of Health has spent $250 million to $300 million to study the health effects of supplements, and “most of the larger NIH-supported clinical trials of DS (dietary supplements) failed to demonstrate a significant benefit compared to control groups.”

Americans’ awareness of that research may be why they’ve stopped using some of the products and been drawn to others, according to the new study.

Fewer Americans are taking multivitamins, for example. That number fell to 31% in 2011-12 from 37% in 1999-2000. Well-publicized studies in that same time period showed that taking multivitamins fails to prevent chronic disease. In fact, in some populations, they could increase mortality risk.

Fewer people are taking vitamins E, C and selenium, perhaps in light of study-based skepticism about antioxidant supplements.

There has, however, been an increase in the number of people using probiotics, lycopene, omega-3 fatty acids and vitamin D.

Recent research has showed that taking vitamin D can reduce fractures and may lower your risk of cancer and cardiovascular problems. Vitamin D consumption saw the biggest increase from 1999-2000 to 2011-12.

Lycopene use also increased among men almost ninefold. Some research, particularly done in the lab and in animals, shows promise for reducing the risk of prostate cancer, but human studies have shown inconsistent results.

The increase in people taking omega-3 fatty acids was mostly driven by a ninefold increase in people taking fish oil. Research shows it may lower a person’s risk for some cancers and cardiovascular disease.

But what about the other vitamins Americans are still taking that don’t show a real health benefit? Part of it may be habit, but an editorial accompanying the latest study, in part, credits the power of advertising and the wide latitude supplement companies have to market their products.

Unlike drugs that require Food and Drug Administration approval to make such claims, supplements don’t go through a rigorous approval process.

Ads do have to carry a warning that says “these statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.” But the editorial concludes that this disclaimer has “minimal effect on consumer understanding of the advertised claim.” Earlier studies suggest that the law, as it stands, has led to much confusion among consumers.