 About 1 in 3 Americans take some multivitamin. Is that helpful, harmful, or just harmless a waste of money? In 2011, the Iowa Women's Health Study reported that multivitamin use was associated with a higher risk of total mortality, meaning in effect women who took a multivitamin appeared to be paying to live shorter lives. But this was an observational study, meaning they didn't split them up into two groups, put half on a multivitamin and see who lived longer. They just followed a large population of women over time and found that those who happened to be taking multivitamins were more likely to die. But maybe they were taking multivitamins because they were sick? The researchers didn't find any evidence of that, but ideally what we'd have is a randomized double-blind placebo-controlled trial, and thousands of people have followed for over a decade, half given a multivitamin, half a placebo, and see what happens. And that's what we got the following year. In 2012, the Harvard Physician studied, too. And after a decade, no effect on heart attack, stroke, or mortality. The accompanying editorial concluded that multivitamins are a distraction from effective cardiovascular disease prevention. The message needs to remain simple and focused. Heart disease can be largely prevented by healthy lifestyle changes. They did, however, find that for men with a history of cancer, the multivitamin appeared to be protective against getting cancer again, though there was no significant difference in cancer mortality or cancer protection in those who've never had cancer before. Still, though, that's pretty exciting. It is just one study, though. Ideally we'd have like 20 of these placebo-controlled trials and then compile all the results together. And that's what we got in 2013. A meta-analysis of randomized controlled trials, 21 of them, covering more than 90,000 individuals and no influence on mortality either way. Some found more cancer mortality, some found less cancer mortality, but all in all, it was a wash. And that was heralded as good news. I mean, after the Iowa Women's Health Study came out, we were worried multivitamins could be harming millions of people. But instead, they don't appear to have much effect either way. The accompanying editorial asked, should meta-analysis trump observational studies? I mean, Iowa Women's Health Study followed tens of thousands of women for nearly 20 years. Well, what if we put all the studies together, the big observational studies, along with the experimental trials? And that's what we got in December 2013, concluding that multivitamins appear to offer no consistent evidence of benefit for heart disease, cancer, or living longer. Why, though? Aren't multivitamins— I mean, aren't vitamins and minerals good for us? Well, one explanation for this result could be that our bodies are so complex that the effects of supplementing a few components is generally ineffective or actually does harm. Maybe we should get our nutrients in the way nature intended. The accompanying editorial concluded, enough is enough. We should stop wasting our money on vitamin and mineral supplements. Americans spend billions on such supplements. A better investment in health would be eating more fruits and vegetables. Now, imagine if we instead spent those billions on healthy food. This is not the aisle we should be getting our nutrients from. With the money we save on pills, we can buy more of the best multivitamins on Earth.