If you take a multivitamin, it’s probably because you want to do everything you can to protect your health. But there is still limited evidence that a daily cocktail of essential vitamins and minerals actually delivers what you expect. Most studies find no benefit from multivitamins in protecting the brain or heart.
So, is it worth taking a multivitamin as part of a healthy lifestyle? Start with asking yourself why you would consider taking a multivitamin. If you suspect your diet is nutritionally lax, focus your efforts there instead.
What we know about multivitamins so far
Despite all the research on vitamins and health, we have only a handful of rigorous scientific studies on the benefits of a “true” multivitamin: a pill that provides essential vitamins and minerals at the relatively low levels that the body normally requires.
The Physicians’ Health Study II was the first large-scale randomized clinical trial to test a commonly taken multivitamin like the ones most people take, containing the daily requirements of 31 vitamins and minerals essential for good health.
More than 14,000 male physicians took either a multivitamin or a placebo pill for more than a decade. The results were mixed, with modest reductions in cancer and cataracts, but no protective effect against cardiovascular disease or declining mental function. This study also was limited by its focus on men.
The COSMOS trial enrolled more than 20,000 older adults (women 65 and older, men 60 and older) to study the effects of two supplements: cocoa extract and a multivitamin. Some participants received one supplement, some received both, and some received only placebos. They were followed for more than three years.
The main COSMOS trial found that multivitamins did not protect against cardiovascular disease or cancer. Three sub-studies focused on cognition (thinking) and memory. They tested participants’ cognition through telephone-based testing (COSMOS-Mind), online testing (COSMOS-Web), and in-person testing (COSMOS-Clinic).
COSMOS-Mind included about 2,200 people. It found an association between taking a daily multivitamin and improved cognition, which was equivalent to about three years less of cognitive aging.
COSMOS-Web included about 3,500 participants. This study also found a cognitive benefit to taking a multivitamin, though it was smaller than the benefit seen in COSMOS-Mind.
COSMOS-Clinic included about 500 participants. This study showed a trend toward improved cognition with multivitamin use, but the results were not conclusive.
A recent analysis of data from more than 390,000 participants from three studies – the National Institutes of Health–AARP Diet and Health Study; the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial; and the Agricultural Health Study – found that taking a daily multivitamin did not decrease the risk of mortality. This study included mostly white participants and did not study other health outcomes.
Guidelines and steps to take
The latest guidelines from the US Preventive Services Task Force – an independent, volunteer panel of national experts – state there is no evidence to support or discourage the use of multivitamins to prevent cardiovascular disease or cancer. The guideline does not address other conditions or overall mortality.
The optimists say that despite no clear evidence of health benefit, multivitamin supplementation is low-risk, low-cost, and may help to fill potential gaps in people’s diets.
For now, you can take certain steps:
Ask your doctor if you really need to take a multivitamin. Could you have a vitamin deficiency?
Assess your diet. Do you eat as healthy as you could? Is anything lacking?
For expert nutrition advice, visit a dietitian.
Do not take high doses of specific vitamins, especially A and E. Overdoing it on these may actually be harmful.
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