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Millions of people take a multivitamin each day. Some believe it’s a sort of insurance in case their diet is missing some essential nutrient. Others believe it will ward off disease by boosting immunity, improving brain health or regulating metabolism.

It’s easy to see where these ideas come from: Ads tout wide-ranging health benefits, even though most offer little or no evidence to back up the claims.

But research on the health benefits of multivitamins has been mixed at best. Last year, for example, the U.S. Preventive Services Task Force, a leading authority on preventive healthcare, reviewed 90 of the best available studies on supplements and vitamins, and concluded the products didn’t protect healthy adults lacking nutritional deficits against cardiovascular disease, cancer or death from all causes. [See “Not everyone needs a daily multivitamin,” published in the May 2023 Beacon.]

Might research on different doses, supplement combinations, or populations prompt a different conclusion? Well, yes — in fact, that may have already happened, according to a new study that focused on memory and brain function.

Multivitamins and brain function

Our current options for improving brain health are limited. For example, regular exercise, optimal weight and a heart-healthy diet can improve cardiovascular health and lower the chances of certain types of dementia, such as dementia due to strokes.

Beyond such common-sense measures, no available medicines, supplements or treatments reliably improve brain function over the long term, despite ads claiming otherwise. That’s why researchers continue to explore whether certain foods or supplements could prove effective.

In a recent study published in Alzheimer’s and Dementia, more than 2,200 volunteers ages 65 and older were randomly assigned to receive cocoa or a placebo, a multivitamin or a placebo, or both cocoa and a multivitamin for three years. (The multivitamin chosen for this study was Centrum Silver, which contains 27 vitamins, minerals and other nutrients in various amounts.)

When cognition tests were analyzed at the end of the trial, those receiving cocoa did not demonstrate any improvement. But those on a multivitamin had improved scores on tests of:

• overall brain function (especially in people with cardiovascular disease)
• memory
• executive function (tasks such as planning ahead or remembering instructions).

Based on these findings, the researchers estimated that three years of multivitamin use could slow age-related decline in brain function by as much as 60%.

Notably, study participants were mostly white (89%), had an average age of 73, and more than half were female (60%). They were followed for only three years. However, it was a randomized, double-blind trial, which is considered the most powerful study design.

Should you take a multivitamin?

This study alone isn’t enough to suggest routine use of multivitamins for people of all ages. It may turn out that the benefits seen in this study were due to deficiencies in certain nutrients among some of the study participants. We don’t know if this is true because it wasn’t part of the study.

Or we might learn that the benefits reported here are too small to make much difference in real life, or wane over time, or have no effect on preventing common types of dementia.

And it’s hard to ignore an earlier randomized, placebo-controlled trial that was actually larger and longer-term: It found no improvement in brain function among male physicians ages 65 and older taking multivitamins.

But it does mean that more study is warranted. We need to understand who is most likely to benefit from multivitamin use, what dose is optimal, and what parts of the multivitamin are most important. We also need larger trials that last longer and include a diverse group of participants.

And certainly, there’s a difference between improving cognitive function and preventing dementia. We still need to know if conditions like Alzheimer’s disease can be prevented by multivitamins or other supplements.

The bottom line

Claims that certain supplements can improve brain health are everywhere you look. But sound scientific evidence backing up those claims is much rarer.

That’s one reason this new study is important: If confirmed, it means that a safe, widely available and inexpensive vitamin supplement could improve quality of life for many millions of aging people. Studies like this one should help science catch up and sort out which claims are valid.

Robert H. Shmerling, M.D., is a senior faculty editor and an editorial advisory board member for Harvard Health Publishing.

© 2023 Harvard University. Distributed by Tribune Content Agency LLC.