Vitamin D: Good for the Bones and the Brain

It can be tough for Canadians to get enough vitamin D in winter, but new research about its impact on dementia makes it all the more important.


Doctors have encouraged vitamin D supplementation for years, as vitamin D is critical for the maintenance of strong bones. Although vitamin D is found in some foods, the majority of it is produced in our skin through sun exposure — and since Canadians spend more than half the year with limited sun exposure, vitamin D supplements are very important to help maintain good health.

Between the ages of 18 and 70, 600 international units (IU) of vitamin D are recommended daily while 800 IU per day are recommended for adults older than 70. To put this into context, during the summer months your body can produce 1,000 IU from just 10 to 15 minutes in the sun.

However, during the winter months — especially in Canada — the sun does not have enough ultraviolet rays for us to produce vitamin D. From November to March it is therefore difficult for Canadians to make vitamin D from the sun alone, which means we should be relying on vitamin D supplements in the winter to reach the daily recommended amount.

Recently, vitamin D supplementation has been gaining more traction in the research world because it may be beneficial for more than just bone health. For example, a new research study published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring found that vitamin D supplements may even have the potential to prevent dementia.

Dr. Maryam Ghahremani, a postdoctoral fellow from the Department of Psychiatry and Hotchkiss Brain Institute at the University of Calgary, led this research study alongside colleagues from the University of Calgary and the University of Exeter.

Over 12,000 participants were selected from Alzheimer’s Disease Research Centres across the United States. Participants were dementia-free at baseline, meaning participants in per-clinical stages of dementia (i.e., mild cognitive impairment) and cognitively normal older adults were included in the study. All participants were around 71 years old, and they were grouped into either the vitamin D supplement group or the non-supplement group.

The main goal of the study was to test the effect of vitamin D exposure on the incidence of a dementia diagnosis determined by participants’ cognitive statuses at study follow-up visits.

The researchers found that participants who took vitamin D supplements had an 84% chance of five-year dementia-free survival compared to a 68% rate for the non-vitamin D supplement participants. Furthermore, exposure to vitamin D was associated with a 40% lower chance of developing dementia. Of the participants that progressed to dementia 10 years after the baseline visit, 75% of them were in the non-supplement group.

All in all, as the researchers hypothesized, exposure to any type of vitamin D supplement was associated with lower dementia incidence. Yet the evidence was stronger for females compared to males, and for those that were cognitively healthy at the baseline visit compared to those with mild cognitive impairment at baseline.

There seem to be many benefits of taking vitamin D supplements, one of them being preventing a diagnosis of dementia. Thus, adding the “sunshine vitamin” to your daily routine is not only necessary to maintain your bone health but potentially also beneficial to maintain optimal cognitive health.

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Alexandria (Alex) Samson is a PhD student in the Department of Psychology at the University of Toronto. She completed her BSc in Neuroscience from Dalhousie University. Alex is a strong believer in open science and is passionate about making scientific research accessible to all audiences.