New research led by University of South Australia scientists supports a causal effect of vitamin D deficiency on brain health, notably for the risk of dementia, but not on stroke risk.
“Vitamin D is a hormone precursor that is increasingly recognized for widespread effects, including on brain health,” said senior author Professor Elina Hyppönen, a researcher with the Australian Centre for Precision Health at the University of South Australia and the South Australian Health and Medical Research Institute, and her colleagues.
“Low 25-hydroxyvitamin D — an indicator of vitamin D status — concentrations are common, and the prevalence of severe vitamin D deficiency ranges from 5% to 50%, depending on location and population characteristics.”
“There are various mechanisms by which active vitamin D may affect the brain, including the regulation of neurotrophic growth factors, influences on inflammation, and thrombosis.”
“With a growing interest in identifying modifiable risk factors for dementia and stroke, vitamin D has become an attractive candidate, as supplementation, diet, and sunlight exposure can maintain adequate serum concentrations.”
In a large-scale prospective study, the authors used information from 33,523 participants of the UK Biobank to examine the association between 25-hydroxyvitamin D concentrations with a range of brain neuroimaging features.
Extending the analyses to 427,690 participants, they also examined the associations with the risks of dementia and stroke using the nonlinear Mendelian randomisation (MR) approach.
Vitamin D deficiency was associated with an increased risk of dementia and stroke, with the strongest associations for those with 25-hydroxyvitamin D concentrations less than 25 nmol/L.
Nonlinear MR analyses confirmed the threshold effect of 25-hydroxyvitamin D on dementia, with the risk predicted to be 54% higher for participants at 25 nmol/L compared with 50 nmol/L.
However, 25-hydroxyvitamin D was not associated with neuroimaging outcomes or the risk of stroke in the MR analyses.
“Our findings are important for the prevention of dementia and appreciating the need to abolish vitamin D deficiency,” Professor Hyppönen said.
“Indeed, in this UK population we observed that up to 17% of dementia cases might have been avoided by boosting vitamin D levels to be within a normal range (50 nmol/L).”
“Larger MR studies are needed to confirm causality for the proposed associations between 25-hydroxyvitamin D concentrations and brain morphometry,” the researchers said.
“Our MR results suggest no clear association with stroke, whereas a causal relation with dementia risk provides an important opportunity for prevention.”
The study was published in the American Journal of Clinical Nutrition.
Shreeya S. Navale et al. Vitamin D and brain health: an observational and Mendelian randomization study. American Journal of Clinical Nutrition, published online April 22, 2022; doi: 10.1093/ajcn/nqac107
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