A new study, which researchers call a “world-first,” describes a direct link between the risk of dementia and a lack of vitamin D.
In the study published in the American Journal of Clinical Nutrition, researchers looked at data and brain scans from more than 300,000 participants from the U.K. to assess the connection.
Dementia is a progressive condition that is characterized by a deterioration of mental capacity, memory and speech, among other effects.
Elina Hyppönen, senior investigator of the study and director of UniSA’s Australian Centre for Precision Health, described it in a press release Tuesday as a “debilitating disease that can devastate individuals and families alike.”
Vitamin D is a crucial part of our health, helping the body to adsorb and retain calcium and phosphorus, critical for building bone. It has also been linked to numerous other benefits, such as reducing cancer cell growth and helping to control infections.
Having a deficiency in vitamin D, on the other hand, can come with a whole host of potential issues. And in Canada, vitamin D deficiency is rampant, according to experts. One report from 2010 stated that between 70 and 97 per cent of Canadians have at least an insufficiency of vitamin D, and that many could have “profoundly deficient levels.”
In this new study, researchers wanted to pinpoint whether a deficiency would have a measurable impact on the brain and on the risk of dementia and stroke.
"Vitamin D is a hormone precursor that is increasingly recognised 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,” Hypponen said in the release.
"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.”
The study used data from the UK Biobank, a cohort that ranged from ages 37-73 at the time of initially signing up. Participants were recruited between 2006 and 2010, and in 2014, around 100,000 participants took part in an imaging subsidy that sought to obtain more information using MRIs of the brain, heart and body.
In this new study, researchers looked at data from more than 33,000 participants from this cohort to compare vitamin D concentrations to brain neuroimaging.
They expanded the data to include disease outcomes, looking at data on more than 294,000 participants across the whole study.
The study excluded participants that had a family history of dementia.
The brain neuroimaging allowed them to look at the brain as a whole, as well as the grey matter, white matter and the volume of the hippocampus, a portion of the brain that plays a major role in memory.
Researchers sought to measure whether there was a casual effect of vitamin D concentrations on brain volume, and how this affected the risk of dementia or stroke.
Previous research into this topic has focused on cross-sections of the brain, and has provided support for the idea that vitamin D levels could impact brain structure. In this study, researchers did not find a direct causal link between vitamin D and brain volume itself, but stated that they did find a causal relationship between vitamin D concentration and the risk of dementia.
Researchers found that there was a connection between those who had a genetically higher level of vitamin D and a decreased dementia risk, “with the odds of dementia decreasing with higher […] concentrations,” the study stated.
The connection strengthened up until a certain point of concentration — 50 nmol/L — after which the connection was less drastic. Researchers suggest that this could mean those who have less than 50 nmol/L concentration could benefit from supplements to boost their levels up to that number. Those with less than 30 nmol/L vitamin D levels are considered to be officially vitamin D deficient.
They adjusted for age, sex, ethnicity, lifestyle, sun exposure and illness-related factors, and researchers stated that while lifestyle and sun exposure affected the results somewhat, the link between vitamin D concentration and dementia persisted regardless, with vitamin D deficiency clearly coinciding with higher dementia risk.
“Potential impact fraction suggests 17 per cent of dementia could be prevented by increasing [vitamin D] to 50 nmol/L,” the study stated, clarifying that these numbers are based on the U.K.
“To our knowledge, this is the first study […] to provide causal evidence for a role of [vitamin D concentration] for which dementia risk appears to operate only below the deficiency threshold.”
Researchers pointed out that there are regions of the world where vitamin D deficiency is more common, making it important to communicate to those populations that vitamin D could be connected to dementia.
According to the study, the prevalence of vitamin D deficiency can range from five to 50 per cent depending on the location and the population.
As of 2013, just over two-thirds of Canadians had blood concentrations of vitamin D greater than 50 nmol/L, according to Statistics Canada, and more Canadians had lower vitamin D concentrations in winter than in summer.
"In some contexts, where vitamin D deficiency is relatively common, our findings have important implications for dementia risks. Indeed, in this U.K. population we observed that up to 17 per cent of dementia cases might have been avoided by boosting vitamin D levels to be within a normal range,” Hypponen said.
"Most of us are likely to be ok, but for anyone who for whatever reason may not receive enough vitamin D from the sun, modifications to diet may not be enough, and supplementation may well be needed."
