Multivitamins: Almost Worthless, But Maybe Not Quite


From Emily Oster:

Many medical studies show positive health effects from higher vitamin levels. The only problem? These studies often can’t tease out the effect of the vitamins from the effect of other factors, such as generally healthy living. Studies that attempt to do this typically show no impact from vitamin use — or only a very tiny one on a small subset of people. The truth is that for most people, vitamin supplementation is simply a waste of time.

Every once in a while I vaguely decide that maybe I’d feel better if I took vitamins. So I buy a bottle of multivitamins and take them for a while. What usually happens next is that I come across yet another in the long parade of news pieces and blog posts reminding me that vitamin supplements are useless. And then I stop again.

I am, needless to say, not talking about specific vitamin supplements recommended by my doctor for a specific condition. I’m talking about the routine use of vitamin supplements. And Oster is right: study after study shows that they’re all but worthless.

And yet! There’s also this from a study released a couple of years ago:

Men who took a daily multivitamin had a statistically significant lower rate of cancer than those who took the placebo (17.0 versus 18.3 events per 1000 person-years). Although mortality was lower as well, it wasn’t statistically significant (4.9 versus 5.6 events per 1000 person-year).

This was an extremely large study, well done, with amazing follow-up. You can’t dismiss it easily.

That’s Aaron Carroll, not generally someone who succumbs to faddish nonsense. The study in question isn’t perfect, but as he says, it’s pretty good. And it suggests that, in fact, multivitamins help reduce the incidence of cancer in men, especially those with a baseline history of cancer. And they’re cheap. So if you happen to be male, maybe multivitamins are worth it after all.