Half of us take some kind of nutritional supplement daily. And sales of these over-the-counter pills are on the rise in the United States, raking in $25 billion annually for the supplement industry.

Among the most popular supplements are multivitamins, which we’re told (and apparently believe) we must take daily to make up for the "lost" nutrients we're not getting in the foods we eat.

But is there any truth to that widely held prescription for health? Does the typical American really need vitamin and mineral supplements?  

No, argues science writer Emily Anthes in an article published last week in the online publication Slate. Not only have recent studies raised serious doubts about the health benefits, if any, of supplemental vitamins and minerals, they also suggest that popping them daily could pose some real medical risks.

Writes Anthes:

[R]esearch on a wide variety of patient populations and medical conditions has failed to find much evidence that multivitamins … prevent major chronic diseases in healthy people. The most recent knock came this spring, when a study of more than 160,000 post-menopausal women, published in the Archives of Internal Medicine, found that the all-in-one pills did not prevent cancer, heart attacks, or strokes and did not reduce overall mortality.

Individual vitamins and minerals haven’t fared much better under scientific scrutiny. ... In 2006, the National Institutes of Health convened an independent panel of experts to evaluate the evidence that vitamins could prevent chronic disease. The scientists ultimately issued a report stating that studies “do not provide strong evidence for beneficial health-related effects of supplements taken singly, in pairs, or in combinations.”

The news on antioxidants, the darlings of the vitamin menagerie, is even more troubling. These compounds, which include vitamins A, C, and E, selenium, beta carotene, and folate, fight free radicals, unstable compounds thought to damage cells and contribute to aging. But not only do antioxidant supplements fail to protect against heart disease, stroke, and cancer; they actually increase the risk of death, according to a 2007 analysis of research on more than 232,000 people, published in the Journal of the American Medical Association, as well as other studies.

Once, when illnesses like scurvy and rickets were common, “placing your bets on a multi might have been reasonable,” Anthes notes. “But today, of course, actual deficiencies are much less common. Our salt, milk, flour, juice, cereal, and more are all fortified with extra nutrients, and a 2009 study published in the Archives of Pediatrics and Adolescent Medicine suggest that most of the kids who end up taking vitamins in the United States today don’t actually need them.”

If vitamins are useful for anything, it’s “probably for tapping into our old friend the placebo effect,” says Anthes. In fact, almost 40 percent of doctors confess that they prescribe vitamins simply because of the pills’ positive effects on their patients’ expectations about getting well. (When people are told that a pill they’re taking is Vitamin C, for example, they report fewer coughs, sneezes and other symptoms of the common cold, even though the pill is actually a placebo.)

There is some “good news for supplements,” acknowledges Anthes, “but it’s extremely limited.” (One of these good-news stories is the benefit that women and their unborn children receive from folic acid supplements taken during pregnancy.)

“But encouraging us to get a complete suite of vitamins [through our diet] is not the same as suggesting that we get them by popping a pill,” says Anthes.

For every study that turns up disconcerting vitamin side effects, there seem to be two more than conclude that we simply don’t know enough yet about supplements to make evidence-based recommendations. Until we do, we should stop treating supplements like health candy and more like prescription meds, to be used only when there’s a demonstrated need. Doctors should create individualized regimes, tailored to a particular patient’s deficiencies. As for the rest of us, we can put the pills back on the shelf and save our cash.