Is It a Good Idea for Adults to Take a Daily Multivitamin?

Millions of Americans take multivitamins, though the supplements’ popularity appears to be fading.

A study published in the Journal of the American Medical Association in October found that the use of dietary supplements of any kind remained stable between 1999 and 2012 at 52% of adults in the U.S. But only 31% of those surveyed in 2011-12 said they took a multivitamin/multimineral product, down from 37% surveyed in 1999-2000.

That decline may reflect in part the release of several studies in the intervening years that questioned whether multivitamins had any benefit in preventing chronic disease.

But this case is hardly closed. Other studies have shown some benefit to taking multivitamins. And some doctors say that no study has yet been conducted with enough people over a long enough time to provide a definitive answer to the question of how effective multivitamins are, if at all, in preventing disease.

So the debate continues, fueled in part by the fact that Americans in general remain notoriously bad eaters and preventive health care in general doesn’t get the attention many doctors feel it merits.

Meir Stampfer, a professor of medicine at Harvard Medical School and professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health, argues in favor of a multivitamin for most people as a safe, inexpensive way to get nutrition that’s missing from their diets. Eliseo Guallar, a professor of epidemiology and medicine at Johns Hopkins University, says multivitamins are an ineffective solution to Americans’ nutritional problems.

YES: People Should Think of Them as Low-Cost Nutritional Insurance

By Meir Stampfer   Brigham and Women's Hospital

I recommend that most people take a multivitamin for one simple reason: Multivitamins are a safe, inexpensive way for people to be sure that they are getting enough of the many vitamins that contribute to good health. They are low-cost nutritional insurance.

That is not to say that multivitamins are in any way a substitute for a healthy diet, or that they rank in importance with other crucial steps that people should take like avoiding smoking, getting plenty of physical activity, maintaining a healthy weight and drinking only moderate amounts of alcohol.

But, because most American adults don’t get optimal levels of all vitamins, multivitamins do have a role to play in maintaining good health.

They can be particularly helpful in combating vitamin deficiencies that can’t be solved by a better diet.

For instance, some vitamin D comes from the diet, but most is made by exposing skin to sunlight. Most Americans have inadequate levels of vitamin D, and this can lead to a wide range of health effects, including reduced bone and muscle strength and greater risk of various cancers.

Another example is B-12 deficiency. Many older individuals don’t get enough of this vitamin despite adequate levels in their diets, because they lack the stomach acid needed to liberate B-12 from food sources. Multivitamins solve that problem because acid isn’t needed to absorb B-12 from supplements. Vitamin B-12 deficiency can contribute to nervous-system disorders including irreversible neuropathy, a condition typified by pain, numbness and weakness in the hands and feet.

Certainly people can take vitamin D or B-12 individually, rather than a multivitamin. But while these are the two most important deficiencies, many people also aren’t getting enough of other vitamins as well, such as B-6 or vitamin A. So it is simpler to take a multivitamin than to take several pills.

And it is better to take a preventive approach than to wait for a deficiency to show up in physical symptoms. The symptoms of B-12 deficiency, in particular, can be subtle and hard to detect until irreversible damage has been done.

What does the research on the health effects of multivitamins show? Such studies are hard to conduct, mainly because it is difficult to tease out the specific impact of the multivitamins from other factors. Most trials have been too small or too short to provide meaningful information.

When you look only at long-term studies, the weight of the evidence points to some small benefit. The most persuasive data comes from the Physicians Health Study II, a 14-year trial among 14,641 physicians. It found a statistically significant 8% reduction in cancer risk.

That is not a big benefit, but given the low cost, safety and ease of taking multivitamins, it seems like a good bargain. Also, physicians tend to be better nourished than others, so one can speculate that the benefits might be bigger in the general population.

It is true, as some critics point out, that not all the mechanisms of exactly how the nutrients in multivitamins contribute to better health have been worked out, but this shouldn’t be a reason not to take multivitamins. Exactly how cigarette smoke causes lung cancer isn't known with certainty, but it still makes sense to advise quitting.

The main downside of taking multivitamins is that it can convey the false impression that by doing so you don’t need to be as concerned about the more important steps you should be taking for your health. But that doesn’t appear to be a widespread problem: Studies have shown that multivitamin users tend to be more health-conscious than others, not less, and have better diets and more health care.

And it’s possible that multivitamin use could help by allowing people to forget about altering their diet to be sure of getting any particular vitamin, and focus instead on the broader aspects of their diet, such as eating the right types of fat and plenty of whole grains, fruits and vegetables.

As long as it’s understood that multivitamins are just a small part of a healthy lifestyle, not a substitute for one, they will have a positive impact on people’s health.