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."
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.
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
Dr. Paul Offit
, author of "Do You Believe in Magic? Vitamins, Supplements, and All Things Natural: A Look Behind the Curtain," has another theory.
"I think people hope that either they won't do any harm, or maybe, just maybe, they will make a positive improvement in their life," Offit said last year.
As a doctor who has helped lead the successful effort to restrict the use of supplements at the Children's Hospital of Philadelphia, he said that since vitamins often "come in the shape of cartoons, they taste like candy," many Americans wonder, "how bad can they be?"
"The problem is, these can be very powerful, and we don't always know what is in them," Sarah Erush
said last year. She is the pharmacy clinical manager and residency director at the Children's Hospital who went to the hospital board to argue for the restrictions.
A 2013 editorial in Annals of Internal Medicine
agreed, concluding, "most supplements don't prevent chronic disease or death, this use is not justified and they should be avoided. Enough is enough."
Yet Americans' faith may be stemming from something else altogether: a desire to be proactive about their health.
"Americans see how limited their doctor's help is," Daniel Fabricant
said last year. The former head of the FDA's division of dietary supplement programs now represents the Natural Products Association. "These products are attractive because they give Americans a chance to take control of their own health. None of us eat enough of a nutritious diet to keep us all healthy. Most of us can't get that perfect body without help. This is an easy way to fill in the gaps."
The association did not respond to a request for comment in relation to the current study.
More research will be done to see whether the current trends continue.