Vitamin D supplementation appears to reduce dementia incidence

Researchers at the University of Calgary in Canada and the University of Exeter in the United Kingdom explored the relationship between vitamin D supplementation and dementia in more than 12,000 participants and found that people who reported taking vitamin D supplements may have a lower risk of developing dementia.

“We know that vitamin D has some effects in the brain that could have implications for reducing dementia; however, so far, research has yielded conflicting results. Our findings give key insights into groups who might be specifically targeted in future studies of vitamin D supplementation,” says principal investigator Professor Zahinoor Ismail, University of Calgary, University of Exeter.

Prospective cohort study

The study in question was a prospective cohort study involving more than 12,000 people in the National Alzheimer’s Coordinating Centre (NACC) database (in the US) who were dementia-free at the outset. Participants were assigned to two groups – those with or without exposure to vitamin D supplementation – and followed to find out how many went on to develop dementia.

Three types of vitamin D supplements were considered: Calcium with Vitamin D, cholecalciferol and ergocalciferol.

Key points

The exposure groups were markedly different at the outset. The vitamin D-exposed group was more educated, had more females, and fewer black participants. In the non-exposed group mild cognitive impairment (MCI) and depression were more common.

Exposure to vitamin D supplementation was associated with a 40% lower dementia incidence than no exposure irrespective of the vitamin D product that was taken.

Of the 2,696 participants who progressed to dementia over 10 years, 2,017 (74.8%) had no exposure to vitamin D throughout all visits prior to dementia diagnosis, and 679 (25.2%) had baseline exposure to vitamin D.

There was no information about vitamin D levels for the participants or about the doses of vitamin D taken. Furthermore, there was no information on exposure to sunlight.

The results suggest that early supplementation of vitamin D, before the onset of cognitive decline may be particularly beneficial i.e. vitamin D may have a role in preventing disease rather that in treating it.

“The link with vitamin D in this study suggests that taking vitamin D supplements may be beneficial in preventing or delaying dementia, but we now need clinical trials to confirm whether this is really the case”, says Dr.Byron Creese, associate professor at the University of Exeter, and co-author.

Next steps

The findings of this study, are now being tested in the VitaMIND study run through PROTECT, an online study based at the University of Exeter. Participants in the treatment group of this randomised, controlled trial are taking vitamin D 4000 IU, once daily.

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Principal investigator Zahinoor Ismail. Riley Brandt, University of Calgary