An editorial in the latest issue of the Annals of Internal Medicine, which published the three studies, put it plainly: "Most [vitamin] supplements do not prevent chronic disease or death, their use is not justified, and they should be avoided. This message is especially true for the general population with no clear evidence of micronutrient deficiencies, who represent most supplement users in the United States and other countries."
That's the thing: There is plenty of evidence that vitamins are beneficial, but only to people who have documented nutrient deficiencies. People in the Western world have access to a diverse array of vitamin-rich foods — from fresh produce to enriched bread, milk, and orange juice — which have made widespread deficiencies mostly a thing of the past. Specific populations, like some young women who are low in iodine and some Mexican-Americans who are more likely to have low iron levels, are the slim exception to the rule.
For the rest of us, most vitamins do zero good. Some supplements can even cause harm: Vitamin E consumption has been linked to an increased risk of prostate cancer, and beta-carotene has been linked to both heart disease and cancer, especially in smokers.
Yet we as a nation continue to spend $28 billion on vitamin supplements each year. NPR's Nancy Shute asked Steven Salzberg, a professor of medicine at Johns Hopkins University, why we keep buying them, despite well-published evidence of their inefficacy. "It seems reasonable that if a little bit of something is good for you, then more should be better for you," he tells NPR. "It's not true. Supplementation with extra vitamins or micronutrients doesn't really benefit you if you don't have a deficiency."
This runs counter to the many, many marketing dollars that supplement manufacturers spend in order to tell you otherwise. A Wall Street Journal article about the 2012 uptick in vitamin sales notes that "supplements appeal because they can tap into the desire for health remedies and claim high prices, without the hassle of tough U.S. regulatory oversight."
But, aren't vitamins just nature's medicine? After all, vitamin C prevents the common cold, right?
Nope. Extensive research has shown that vitamin C has almost no effect on the common cold, except under highly specific circumstances. How did this common un-wisdom get spread in the first place? A July article from The Atlantic points to Nobel prize-winning chemist Linus Pauling, who was a major advocate for vitamin C's supposed benefits. "Although study after study showed that he was wrong, Pauling refused to believe it, continuing to promote vitamin C in speeches, popular articles, and books," writes Paul Offit. "When he occasionally appeared before the media with obvious cold symptoms, he said he was suffering from allergies."
That was over 40 years ago. Today, we have more reason than ever to take our supplements with a grain of salt. If you think you really need a vitamin, talk to your doctor. They'll know better. (NPR)