New research suggests that low vitamin D levels are associated with lower brain volumes and an increased risk of dementia and potentially stroke.
Genetic research from the University of South Australia (UniSA) has found a direct link between dementia and a lack of vitamin D.
The studyPosted in The American Journal of Clinical Nutritioninvestigated the association between vitamin D, neuroimaging characteristics, and risk of dementia and stroke, concluding that:
- low vitamin D levels were associated with lower brain volumes and increased risk of dementia and stroke
- genetic analyzes supported a causal effect of vitamin D deficiency and dementia
- in some populations, up to 17% of dementia cases could be prevented by increasing normal vitamin D levels (50 nmol/L).
Supported by the National Health and Medical Research Council, the genetic study analyzed data from 294,514 participants from the UK Biobank, examining the impact of low levels of vitamin D (25 nmol/L) and the risk of dementia and diabetes. ‘stroke.
Lead researcher and director of UniSA’s Australian Center for Precision Health, Professor Elina Hyppönen, says the findings are important for the prevention of dementia and for appreciating the need to abolish vitamin D deficiency.
“Vitamin D is a hormone precursor that is increasingly recognized for its widespread effects, including on brain health, but so far it has been very difficult to examine what would happen if we could prevent vitamin D deficiency,” she said.
“Our study is the first to examine the effect of very low levels of vitamin D on the risk of dementia and stroke, using robust genetic analyzes among a large population.
“In some settings, where vitamin D deficiency is relatively common, our findings have important implications for dementia risk. Indeed, in this UK population, we observed that up to 17% of dementia cases could have been prevented by raising vitamin D levels to within a normal range.
Nonlinear Mendelian (MR) randomization – a method of using measured variation in genes to examine the causal effect of modifiable exposure on disease – was used to test the underlying causality of neuroimaging findings , dementia and stroke.
Although the MRI results suggested no clear association with stroke, they did confirm a causal relationship with dementia risk, which the researchers said offers an “important opportunity for prevention”.
Similarly, the finding that the greatest effects on dementia risk were seen in people with the lowest vitamin D levels (
For Professor Hyppönen, the results are significant given the high prevalence of dementia around the world.
“Dementia is a progressive and debilitating disease that can devastate individuals and families,” she said.
“If we are able to change this reality by ensuring that none of us are seriously deficient in vitamin D, that would also have other benefits and we could change the health and well-being of thousands of people. .”
“Most of us are probably fine, but for anyone who, for whatever reason, is not getting enough vitamin D from sunlight, dietary changes may not be enough and supplementation may be necessary.”
Researchers think it’s “biologically plausible” that vitamin D may have a protective effect on brain health, suggesting three possible mechanisms
“First, the presence of vitamin D receptors in the hypothalamus suggested a neurosteroid function for active vitamin D, promoting neuronal growth and maturation,” they wrote.
“Second, there may be vascular mechanisms, as active vitamin D has been associated with reduced thrombosis and regulation of the renin-angiotensin system.
“Third, full concentrations of active vitamin D may act neuroprotectively by suppressing excessive inflammatory neurovascular damage caused by pro-inflammatory cytokines and attenuation of amyloid proteins, commonly seen in Alzheimer’s disease.”
Limitations of the study cited by the research team include an inability to rule out residual confounding influences in their observational analyses, while the UK biobank was labeled “vulnerable to healthy volunteer bias” because the reference population was mostly less deprived, had an intermediate to high education, and had a normal to overweight BMI (50).
Meanwhile, as the MR analyzes were limited to participants of White British ancestry, these results may not be generalizable to other populations.
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