Many people see vitamins as an inexpensive and risk-free way to prevent disease. But just as the Holy Roman Empire was neither holy, nor Roman, nor an empire, vitamins are neither inexpensive nor risk free, and they do not actually prevent disease. In fact, they may make things worse.
Last week, the United States Preventive Services Task Force published its recommendations about whether vitamins, minerals and nutritional supplements should be taken to prevent cardiovascular disease and cancer. Much as it did in 2014 when it last reviewed the evidence, it explicitly recommends against taking beta-carotene or vitamin E, and says there is insufficient evidence to support the use of any other vitamins.
In short, vitamins don’t work. In fact, beta-carotene increases the risk of cancer and vitamin E increases the risk of hemorrhagic strokes.
So why do people keep taking them?
Amazingly, negative vitamin studies don’t seem to dent sales, which amount to billions of dollars globally. When asked, most people say they take vitamins to improve their health, but, paradoxically, when you look at data from the National Health and Nutrition Examination Survey the people who take vitamins are more likely to be in good health to begin with. They smoke less, exercise more and have lower rates of obesity. Also, when you survey people about their vitamin use, you unveil surprisingly contradictory beliefs. Almost 90 percent of people surveyed agree or strongly agree that vitamins can help people meet their nutritional requirements. But 80 percent of them also agree or strongly agree that vitamins shouldn’t be used as a substitute for an unhealthy diet, and 75 percent agree or strongly agree that vitamins are not meant to cure disease.
When you drill down into people’s perceptions, they at once acknowledge that vitamins do not cure disease and yet simultaneously see them as boosting health.
Some people do have valid medical reasons to take vitamins; vitamin deficiencies do happen. But vitamin deficiencies are extremely rare.
That leaves many people taking vitamins for reasons that are not medically justifiable. A survey of Italian students found that those taking supplements were not taking them because they were worried about not getting enough vitamin D, iron or omega-3. The most common reason given was to boost athletic performance, even though there is little evidence to support this idea.
This belief system is incredibly difficult to dislodge. The editorial accompanying the USPSTF recommendations discusses why this may be the case. Rather successful marketing continues to convince the public that vitamin supplementation has value, when it largely does not. Vitamins are seen as natural and people who abhor “Big Pharma” and taking medication happily take a vitamin supplement while being blissfully unaware that prescription drugs and vitamins are often made by the same company. Also, people often prefer to do “something” even when that something is contrary to their self interest. Statistically, a soccer goalie’s best strategy is to stay in the center of the net during a penalty kick. And yet goalies feel compelled to dive one way or the other because in that setting inaction is unacceptable. The term has a name: action bias. It is what compels some of us to honk our car horns in traffic when we know it will have little effect.
Humorous examples aside, the problem with our vitamin fascination is that only one-quarter of people who take vitamins would stop taking them if advised to do so by public health. While it is understandable to want to take your health in hand, there are better, cheaper things you can do. Quit smoking, exercise regularly, eat plenty of fruits and vegetables, avoid junk food, and you will drastically reduce your risk of both cancer and heart disease. Simply take vitamins, and you will not.
Christopher Labos is a Montreal physician and cohost of the Body of Evidence podcast.
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