Americans have been sold on vitamins and supplements. Fully half of us take one or more of them. We buy so many of them that we have created a $30,000,000,000 industry.
Is this yet another instance of our pill popping ways, our sense that we can cure and prevent all ills by throwing something down our throats?
Those who have been touting the health benefits of vitamins appear to have science on their side. By all appearances, however, the science was skewed. New studies, reliably controlled for all extraneous factors, tell a very different story.
Emily Oster reports on research into the effectiveness of Vitamin E and Vitamin D:
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.
The bottom line is that there is simply very little evidence that these supplements matter. The best-case scenario is if you are an elderly woman who is deficient in vitamin D — then a supplement might help a little. Still, in the 2009-2010 NHANES, about 30 percent of the non-elderly-female population took supplements.
And then there is the cult-like following commanded by Vitamin C. And, who doesn’t take a multivitamin?
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. Of course there are exceptions — folic acid is generally a good idea for pregnant women — but the data increasingly suggests that most people simply do not benefit from supplements.
Past studies went wrong because they did not control for factors like education level, wealth and social class:
For example, highly educated people are more likely to take vitamins but less likely to be overweight and have diabetes — and being overweight and having diabetes are associated with a host of health problems. This makes it virtually impossible to separate the impact of vitamins from the impact of these other variables. We know education and race are also very strongly linked to mortality rates. Given this backdrop, it is an almost insurmountable challenge to tease out any small impacts of vitamins.
Fair enough. People who are better educated have healthier lifestyles and are less likely to be overweight. Therefore they are less likely to have diabetes and high blood pressure. And these are the people who are most likely to take vitamins. Ergo: correlation does not necessarily bespeak causation.
But how does it happen that those who are better educated are most easily duped into buying and ingesting substances whose value is dubious at best?
Does their belief in the benefits of vitamins reduce anxiety and thus contribute to better health? Are vitamins and supplements the ultimate placebos?