Preventing dementia: Are vitamin and mineral supplements worth the money?

The Bottom Line

  • Globally, approximately 50 million people have dementia, making prevention a top priority.  
  • Research shows that there is currently not enough good evidence to support the use of vitamin and mineral supplements for the prevention of cognitive decline in people with or without cognitive impairment. 
  • There are other promising strategies, such as physical and cognitive exercise, which may improve cognitive function

The number of people with dementia is rising dramatically (1;2). Take for example Canada. One in four Canadians aged 85 and over have been diagnosed with the condition, with the number of people diagnosed more than doubling every five years (1). Worldwide, about 50 million people suffer from dementia, costing more than $948 billion annually (2;3). Based on these stats, it’s no surprise that preventing dementia is top-of-mind for people, informal caregivers, health care providers, and policymakers alike.

Dementia—which is most commonly caused by Alzheimer’s disease (4-6)—is a decline in cognitive ability (4). It affects things like memory, understanding, language, and problem solving skills. Dementia gets worse over time and can significantly impact quality of life and a person’s ability to carry out everyday activities (4).

Before a person has dementia, they might experience Mild Cognitive Impairment, also known as MCI (4). In a person who has MCI, cognitive changes go beyond what is expected with aging, but daily functioning is not severely affected (4). For example, when MCI is present, changes in memory, judgement, and thinking can lead to increasing forgetfulness, greater impulsivity, and getting sidetracked when speaking or reading (7). However, these changes are not severe enough to interrupt one’s ability to complete daily routine activities (4).

It is now known that the changes that lead to dementia or MCI begin long before symptoms appear (4;8), which provides an opportunity to prevent the onset of the disease. One popular idea is that vitamins or minerals (or both) can ward off cognitive decline. Vitamins and minerals are needed to keep the body running smoothly (4;9), and can be found naturally in the foods we eat or purchased as over-the-counter supplements (4;10).

Over-the-counter supplements are a booming business, with consumers spending billions of dollars on them every year. But, when it comes to dementia prevention, are they worth the money?

What the research tells us

One systematic review compared people taking vitamins or minerals—specifically vitamins A, B, C, D, and E, beta-carotene, calcium, zinc, copper, folic acid, selenium, and multivitamins—to people who did not. This review found no evidence that taking vitamins or minerals prevented dementia or cognitive decline among middle-aged or older adults with no signs of existing cognitive decline. Although some studies in the review found that vitamin C and beta-carotene may lead to better overall cognition when taken over the long-term (for 5 to 18 years), because these studies were of low-quality, it’s not clear if the results are trustworthy (4).

Another systematic review looked at over-the-counter supplements—specifically vitamins B, C, D, E, beta-carotene, omega-3 fatty acids, gingko biloba soy, folate, calcium, and multivitamins—and found similar results, that currently there is not enough evidence to support the use of over-the-counter supplements to prevent cognitive decline. This was found for both adults with normal cognition, as well as those with MCI. It’s also worth mentioning that two of the studies in this review showed that folic acid and vitamin B12 might improve memory when taken for two years, but again, the studies were of low-quality (9).

So, where does this leave us?

While the current research shows that vitamins and minerals may not prevent cognitive decline or dementia, hope is not lost. Research has revealed that exercise—for both your body and your brain—may help improve cognitive function.

Get the latest content first. Sign up for free weekly email alerts.
Author Details


  1. Canadian Institute for Health Information. Dementia in Canada: Summary. [Internet] 2019. [cited August 2019]. Available from
  2. World Health Organization. Dementia. [Internet] 2019. [cited August 2019]. Available from
  3. Xu J, Zhang Y, Qiu C, et al. Global and regional economic costs of dementia: A systematic review. Lancet. 2017; 390(4):S47. doi: 
  4. Rutjes AW, Denton DA, Di Nision M, et al. Vitamin and mineral supplementation for maintaining cognitive function in cognitively healthy people in mid and late life. Cochrane Database Syst Rev. 2018; 12:CD011906. doi: 10.1002/14651858.CD011906.pub2. 
  5. Jellinger KA. Clinicopathological analysis of dementia disorders in the elderly - An update. J Alzheimers Dis. 2006; 9(3 Suppl):61-70. 
  6. World Health Organization and Alzheimer’s Disease International. Dementia: A public health priority. [Internet] 2012. [cited August 2019]. Available from:
  7. Mayo Clinic. Mild cognitive impairment (MCI). [Internet] 2019. [cited August 2019]. Available from
  8. Sperling RA, Aisen PS, Beckett LA, et al. Toward defining the preclinical stages of Alzheimer’s disease: Recommendations from the National Institute on Aging and the Alzheimer’s Association workgroup. Alzheimers Dement. 2011; 7(3):280-292. doi: 10.1016/j.jalz.2011.03.003. 
  9. Butler M, Melson VA, Davila H, et al. Over-the-counter supplement interventions to prevent cognitive decline, mild cognitive impairment, and clinical Alzheimer-type dementia: A systematic review. Ann Intern Med. 2018; 168:52-62. doi: 10.7326/M17-1530.
  10. Kennedy DO, Haskell CF. Vitamins and cognition: What is the evidence? Drugs. 2011; 71(15):1957-1971. doi: 10.2165/11594130-000000000-00000.

DISCLAIMER: These summaries are provided for informational purposes only. They are not a substitute for advice from your own health care professional. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the McMaster Optimal Aging Portal (

Many of our Blog Posts were written before the COVID-19 pandemic and thus do not necessarily reflect the latest public health recommendations. While the content of new and old blogs identify activities that support optimal aging, it is important to defer to the most current public health recommendations. Some of the activities suggested within these blogs may need to be modified or avoided altogether to comply with changing public health recommendations. To view the latest updates from the Public Health Agency of Canada, please visit their website.