Should We Take a Multivitamin?
About one in three Americans take a multivitamin. Is that helpful, harmful, or just a harmless 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 that women who took a multivitamin appeared to be paying to live shorter lives. But this was just an observational studyóresearchers didnít split women up into two groups and put half on multivitamins to see who lived longer. All they did was follow a large population of women over time, and found that those that happened to be taking multivitamins were more likely to die. But maybe they were taking multivitamins because they were sick. The researchers didnít find any evidence of that, but ideally weíd have a randomized, double-blind, placebo controlled trial, where thousands were followed for over a decade, with half given a multivitamin and half a placebo. Thatís what we got the following year in 2012. The Harvard Physiciansí Study II. And after a decade, the researchers found 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.
The researchers 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 whoíve never had cancer before. Still, thatís pretty exciting. It is just one study, though. Ideally weíd have maybe 20 of these placebo-controlled trials and then compile all the results together. Thatís what we got in 2013óa meta-analysis of randomized controlled trials that analyzed twenty-one trials and more than 90,000 individuals. The analysis found 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. After the Iowa Womenís Health Study came out we were worried multivitamins could be harming millions of people, but instead they donít appear to have much effect either way. The accompanying editorial asked whether meta-analyses trump observational studies. The Iowa Womenís Health Study followed tens of thousands of women for nearly 20 years. What if we put all the studies together, the big observational studies along with the experimental trials? And thatís what we got in December 2013. The review for the U.S. Preventive Services Task Force found that multivitamins appear to offer no consistent evidence of benefit for heart disease, cancer, or living longer.
But arenít vitamins and minerals good for us? One explanation for this result could be that our bodies are so complex that the effects of supplementing with only one or two components is generally ineffective or actually does harm. Maybe we should get our nutrients in the way nature intended.
The accompanying editorial to the December 2013 review concluded that enough is enough. We should stop wasting our money on vitamin and mineral supplements. Americans spend billions on vitamin and mineral supplements. A better investment in health would be eating more fruits and vegetables. Imagine if instead we spent those billions on healthy food?
With the exception of vitamins D and B12 (Vitamin Supplements Worth Taking), we should strive to get our nutrients from produce, not pills.
Michael Greger, M.D.
PS: If you havenít yet, you can subscribe to my free videos here and watch my live year-in-review presentations†Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.