If you think you do, then chances are you've fallen victim to one of the biggest scams of modern times. It's not much different than the pitches made by snake oil salesmen over one hundred years ago. There are people making big money by convincing gullible citizens that they have vitamin deficiencies. Some of those people are doctors and many of the enablers are family physicians who don't know the scientific evidence behind vitamin supplements.
"There's a sucker born every minute."
(frequently attributed to P.T. Barnum)The Atlantic has published a nice summary of the current evidence: The Vitamin Myth: Why We Think We Need Supplements. Most of the article is about Linus Pauling and why he was spectacularly wrong about vitamin supplements. Here's the bottom line ...
On October 10, 2011, researchers from the University of Minnesota found that women who took supplemental multivitamins died at rates higher than those who didn't. Two days later, researchers from the Cleveland Clinic found that men who took vitamin E had an increased risk of prostate cancer. "It's been a tough week for vitamins," said Carrie Gann of ABC News.I'm not convinced that moderate amounts of vitamin supplements will actually cause you much harm—the jury's still out on that IMHO. However, it's now abundantly clear that, for the average healthy person, spending money on vitamin supplements is no different that flushing that money down the toilet, which, coincidentally, is where most of the vitamins you take will eventually end up.
These findings weren't new. Seven previous studies had already shown that vitamins increased the risk of cancer and heart disease and shortened lives. Still, in 2012, more than half of all Americans took some form of vitamin supplements.
See also: What Kind of People Take Vitamins?.