nutrition

Your Daily Multivitamin Is Pointless, at Best

Be it in pill form or gummy, Americans love a vitamin. The industry tops $30 billion a year, with 85 percent growth since 2005 according to some estimates, and recent national statistics show that nearly half of adults in the U.S. take some sort of dietary supplement. 

But is all this vitamin-popping actually making us healthier, or is this just another health fad unsupported by nutrition science? Over at FiveThirtyEight this week, University of Chicago economics professor Emily Oster digs into some of the data, citing some recent studies that suggest, however well-intentioned it is, a daily multivitamin habit may be an exercise in futility. Two large studies — one called the Physicians’ Health Study, from Harvard researchers, and the other called the Women’s Health study, from the National Institutes of Health — found no association between a daily vitamin supplement and improved health.

Oster explains:

When the results of these studies came out, they largely refuted the idea that these supplements offered benefits. Vitamin E appears to have no impact on cancer or heart disease. Results from the Women’s Health Study, released in 2005, showed no relationship between vitamin E supplementation and overall mortality. Later results from the men in the Physicians’ Health Study showed the same: no relationship.

For vitamin D, the randomized trials (nicely summarized here) refuted virtually all of the purported benefits to diabetes, weight loss and cancer. For elderly women, there is some evidence of a small reduction in mortality with supplementation, but well below what was seen in observational data and only marginally statistically significant. … And it’s not just vitamins D and E. The Physicians’ Health Study also looked into vitamin C and a one-a-day multivitamin and found the same results: no impacts on cancer or cardiovascular disease

But what’s more, taking a daily multivitamin can actually backfire on those concerned with health. According to a 2011 paper in Psychological Science, people who believed they’d taken a vitamin were apparently so pleased with themselves for their efforts at health that they reported a greater desire to engage in more potentially harmful activities — like tanning, heavy drinking, or gorging themselves at a buffet — than those who hadn’t taken a vitamin. (In reality, both groups were given placebo pills.)

Psychologists call this idea moral “licensing,” and Wray Hubert at the Association for Psychological Science explains the notion further:

Licensing is the notion that when we do something that we believe is good for us—like popping a vitamin—this action ironically gives us permission to engage in subsequent bad behavior—like munching potato chips—adding up to a net loss. We make these perverse tradeoffs because doing something positive bolsters our “health credentials,” which boosts our sense of invulnerability, which in turn encourages self-indulgence.

It’s the same reason why you feel entitled to a gigantic everything bagel with cream cheese after going for an early morning run (to take an example that may or may not be from my own life). In any case, unless you’ve been explicitly instructed to take vitamins by a health professional — or, you know, if you just dig the taste of gummy vitamins, which is fair enough — you can probably skip them.

Your Daily Multivitamin Is Pointless, at Best