F.Birchman / MSNBC.com
By
msnbc.com contributor
updated 3/2/2006 4:56:58 PM ET 2006-03-02T21:56:58

If you’ve ever suspected those cure-all claims for dietary supplements were too good to be true, you’re in some pretty good company.

Two recent studies appearing in the highly-respected New England Journal of Medicine punctured the promises of some of the most popular pills found on drug-store shelves.

Turns out calcium isn't much help for preventing broken bones as we grow older. And glucosamine and chondroitin sulfate, top-sellers for the aches and pains of osteoarthritis, hardly make a difference.

Vitamins C and E fared even poorer as preventives against prostate cancer in a study last week in the Journal of the National Cancer Institute. It found no reduction of risk whatsoever, except perhaps in some smokers.

"People have been seeing supplements as all they needed to do to avoid disease,’" says Dr. Meir Stampfer, professor of nutrition and epidemiology at the Harvard School of Public Health. "These studies provide a wake-up call to say, no, you need to do more than that.’’

Could the $5 billion dietary supplement industry finally be losing its luster?

Andrew Vickers, Ph.D., a research methodologist in the Integrative Medicine Service at Memorial Sloan-Kettering Cancer Center in New York City, say the recent spate of studies -- including one last year that showed echinacea didn't fight the common cold after all -- doesn't signal a downward plummet. Instead, it's a more accurate reflection of the more limited benefits many supplements offer.

"Small trials, which many supplements have gone through, often show a great deal of benefit,’’ says Vickers. "It’s only when you greatly increase the size of the population studied that you are able to see a more accurate picture, which is what we’re seeing now.’’ 

For example, just over 36,000 women, ages 50 to 79, were enrolled in the calcium study, a large number for a clinical trial. Half the participants were given placebos, the others received 1,000 mg of calcium and 400 iu of vitamin D, just slightly less than the National Osteoporosis Foundation's guidelines of 1,200 mg of calcium and 400-800 iu of vitamin D for women over 50. 

'If it works for me...'
Clear benefit was seen only for women over 60; hip fractures in that group were reduced by 21 percent. But overall, women in the supplement group did not have fewer fractures than women who took the placebo.

And in the 30,000-strong osteoarthritis study, patients with mild joint pain saw no improvement by using glucosamine and chondroitin, though there was some relief for people with more severe pain.

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Even industry members think the studies may lead to a recalibration of an over-hyped industry. "Marketers tended to go overboard with their claims -- so instead of suggesting support for a particular area of health, many implied curative effects,’’ says Shawn Talbott, editor of an industry Web site, SupplementWatch. "When supplements are actually studied for those curative effects ... they do not always fare so well,’’ Talbott says

Rather than push consumers away, experts hope the studies will relegate supplements to a complementary role, amid a host of other healthy efforts.

The National Osteoporosis Foundation posted a notice on its Web site saying the latest findings would not change the group’s calcium and vitamin D recommendations but reminded women that bone health also requires other steps such as weight-bearing exercise. 

Dr. Mary Jo DiMilia, an integrative medicine physician at Mount Sinai Medical Center, says none of her patients have asked about foregoing calcium, and she’s not giving up the glucosamine she’s relied on to relieve arthritis pain for the last two years. "If it works for me,’’ asks DiMilia, "why should it matter that the study didn’t find benefit for all patients?"

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