Do you really need all those pills? Some researchers say dietary supplements help only those who need them, and don't make healthy people healthier.

“Don’t forget to take your vitamins?”

That healthful reminder from mom may soon become a thing of the past. While dietary supplements remain popular in the US, a continuous stream of studies are casting increasing doubt that the widely-accepted benefits are real. Researchers and regulators are taking notice, and some are beginning to deliver a different message.

Two studies published earlier this month are the most recent examples. One takes aim at vitamin E, the other at multivitamin supplements for women.

The Selenium and Vitamin E Cancer Prevention Trial (SELECT) put to test the common “wisdom” that vitamin E lowers men’s risk for prostate cancer. A total of 35,533 men in the US, Canada, and Puerto Rico, received one of four treatments: vitamin E, selenium (an essential mineral thought to lower the risk of cancer when taken with vitamin E), both together, or a placebo. They found that taking vitamin E actually increased the risk for prostate cancer. Taken together with selenium, however, seemed to mitigate the increased risk that comes with taking vitamin E.

Bottom line, though, is that taking vitamin E or selenium – or both – did not reduce risk of prostate cancer.

The Iowa Women’s Health Study assessed the health affects of vitamins and minerals in over 38,000 older women. With a maximum follow up of about 20 years, the study showed that taking common vitamins and mineral supplements was actually associated with an increase in mortality rate, compared to women who did not take supplements.

We have to keep in mind, though, that studying the effects of vitamins and supplements is tricky. People don’t just eat them one at a time. The subjects in the SELECT trial took their vitamin E along with their normal diet. Other vitamins and minerals can interact with vitamin E in complex ways that researchers are far from understanding. So studies that try to parse out the effects of a single supplement have to be taken, pardon me for saying, with a grain of salt.

But while any single trial is not conclusive, a pattern emerges when one takes a broader view, according to Marion Nestle, New York University professor of nutrition, food studies, and public health. “The better the quality of research, the less benefit [supplements] show,” he told the Wall Street Journal. “It’s fair to say from the research that supplements don’t make healthy people healthier.”

There's nothing like the real thing.

Others agree. The Office of Dietary Supplements, part of the National Institutes of Health, says that while vitamin C has long been a popular remedy for the common cold, research shows that, for most people, vitamin C does not reduce the risk for getting a cold. On the other hand, taking too much vitamin C can cause diarrhea, nausea, and stomach cramps. And while taking vitamin B-6 and B-12 is commonly thought to reduce risk for cardiovascular disease, the data is not conclusive. In a 2006 statement, the American Heart Association said “evidence is inadequate to recommend...B vitamin supplements as a means to reduce cardiovascular disease risk.” There’s no disputing that calcium is important for bone health, but efforts to show it reduces the risk of cancer and heart disease have fallen short. And taking calcium supplements can increase risk for kidney stones.

Early studies suggested beta-carotene decreased risk for lung cancer. But two large studies published in 1994 and 1996 showed that smokers taking beta-carotene supplements were actually more likely to develop lung cancer than smokers who didn’t take the supplement. A follow up to the studies was performed in 2004. It concluded that beta-carotene was harmful to those at risk for lung cancer, even though the subjects hadn’t taken the supplement for years.

But that doesn’t mean all of us should stop taking our vitamins. For those with specific deficiencies or the malnourished, supplements are a necessary part of the diet. It’s recommended, for example, that pregnant women take folic acid. Folic acid is important for the kind of rapid cell growth that occurs during pregnancy. Taking it helps reduce the risk of birth defects.

Large studies that evaluate supplements, such as SELECT, are rare. In fact, many supplements remain untested, not only for their effectiveness, but for their safety as well. The FDA has a separate set of regulations for supplements than they do for drugs or “conventional” foods. According to these regulations, the “manufacturer is responsible for ensuring that a dietary supplement or ingredient is safe before it is marketed.” The FDA is responsible, however, for taking action if a supplement has adverse effects once people start taking them.

Sounds arse-backwards if you ask me. But no one’s asking me, and the fact is the supplement industry is big business. According to a National Health and Nutrition Examination Survey report published earlier this year, in 2006 about half of Americans were popping at least one supplement a month. In 2010 the supplement industry raked in $28 billion in sales, a 4.4 percent increase from 2009. Despite the growing number of studies that show a given supplement doesn’t work, people continue to take them.

Joseph Fortunato, chief executive of supplement retail giant GNC Corp., is quite okay with that. The Wall Street Journal quotes Fortunato from a company conference call transcript: “The thing you do with [reports of studies] is just ride them out, and literally we see no impact on our business.”

That may soon change if the National Center for Complementary and Alternative Medicine (part of the NIH) and other health institutes have their way. The growing body of data that consistently fails to show benefits has prompted them to push for more studies that explore how nutrients work – a body of knowledge that is surprisingly lacking.

So what do we do with all this uncertainty? If you’re considering taking a dietary supplement, get informed. Read up and talk to your doctor. But as professor Nestle says, it might be a waste of money for people without specific deficits. The best way to get the vitamins and minerals you need? The old fashioned way: a balanced diet.

[image credits: Johns Hopkins Bloomberg School of Public Health and Dietary Supplements For Health And Fitness]
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Peter Murray was born in Boston in 1973. He earned a PhD in neuroscience at the University of Maryland, Baltimore studying gene expression in the neocortex. Following his dissertation work he spent three years as a post-doctoral fellow at the same university studying brain mechanisms of pain and motor control. He completed a collection of short stories in 2010 and has been writing for Singularity Hub since March 2011.