Healthy vitamin D levels reduce the risk of dementia

There is a direct link between low vitamin D levels and the development of various forms of dementia. Researchers at the University of South Australia analysed data from nearly 300,000 adults and found that in Western countries, 17 percent of dementia cases could be prevented if no one's vitamin D level fell below 50 nanomoles/L.

Most Dutch doctors consider a vitamin D level of 50 nanomoles/L to be the minimum that healthy people should have, but more and more endocrinologists believe that this guideline is too modest. The international Endocrine Society, for example, believes that this minimum value should be 75 nanomoles/L.

While the debate about the optimal amount of vitamin D is far from over, it is already clear that large groups of people are not getting enough vitamin D. One in three Dutch people have vitamin D levels below 30 nanomoles during the winter months. You can read more about this, and about ways to normalise low vitamin D levels, here.

The study published by the Australians in the American Journal of Clinical Nutrition is a scientific achievement for several reasons. To begin with, the researchers had access to data from a large number of study participants, which had also been collected by well-trained healthcare professionals and scientists. This was done in England, as part of a project called UK Biobank.

The study participants were aged 37-73 when the study began. The researchers were able to follow them for 10-14 years. The researchers knew the vitamin D levels in the subjects' blood and their lifestyle. The Australians therefore also knew how much the participants exercised and how often they were exposed to the sun. In addition, the Australians knew a number of important genes of the study participants that influenced the functioning of vitamin D in the body.

Thanks to the large amount and quality of the data, as well as new statistical methods, the Australians were able to filter out not only the effect of lifestyle, but also the effect of genes. This had never been done before.

‘Vitamin D is a hormone that is increasingly recognised as influencing many, many aspects of our health,’ said research leader Elina Hyppönen in a press release. "This also applies to the health of our brains. Until now, it has been particularly difficult to estimate what would happen if we could eliminate vitamin D deficiency on a large scale. Our research is the first of its kind."

The Australians found that adequate vitamin D levels not only had a positive effect on dementia, but also reduced the risk of stroke by raising vitamin D levels from too low to healthy.

Navale (2022), Vitamin D and brain health: an observational and Mendelian randomization study. 

University of South Australia (2022), Vitamin D deficiency leads to dementia (Press Release).