Genetic research has found a direct link between dementia, one of the major causes of disability and dependency among older people, and a lack of vitamin D. The researchers believe their findings could significantly help to prevent dementia while raising awareness of the need to abolish vitamin D deficiency.
Currently, about 50 million people around the world suffer from dementia and this number is expected to increase almost three times by 2050. It’s an incurable neurogenerative disease of unknown cause. Alzheimer's disease is the most common type of dementia, with a median age of diagnosis of 80 years old.
Researchers have long been exploring relevant preventive interventions to delay the development of dementia. Several relevant risk factors have been identified (including smoking, hypertension, cardiovascular disease, overweight, and vitamin D deficiency), but there was relativelly little evidence regarding them.
It’s been suggested vitamin D could play a role in the progression of dementia due to its role in neurotrophy, neurotransmission, and neuroplasticity. However, the conclusions of studies have been contradictory. Organisms obtain vitamin D either by exposure to sunlight or through food intake, from oily fish, red meat, liver, and egg yolks.
Researchers at the University of South Australia investigated the link between vitamin D, neuroimaging features, and the risk of dementia and stroke. They went through data from almost 295,000 participants from the UK Biobank, measuring variation in genes through nonlinear mendelian randomization (MR).
“Vitamin D is a hormone precursor that is increasingly recognized for widespread effects, including on brain health, but until now it has been very difficult to examine what would happen if we were able to prevent vitamin D deficiency,” Elina Hyppönen, one of the study authors, said in a statement.
The study confirmed that low levels of vitamin D are associated with lower brain volumes and a higher risk of dementia and stroke. The analysis also suggests a causal effect between vitamin D deficiency and dementia, and that in some populations up to 17% of the dementia cases could be prevented by getting vitamin D levels back to normal (with the caveat that the study has been carried out on participants in Britain).
“Our study is the first to examine the effect of very low levels of vitamin D on the risks of dementia and stroke, using robust genetic analyses among a large population,” Hyppönen said. “In some contexts, where vitamin D deficiency is relatively common, our findings have important implications for dementia risks.”
The researchers also said the findings are very significant considering the high prevalence of dementia around the world and the expected trends. For anyone not getting enough vitamin D from the sun, modifications to the diet might not always be enough, Hyppönen said, suggesting the use of supplementation when needed.
The study was published in the American Journal of Clinical Nutrition.