For years, scientists have conducted studies that found vitamin D deficiency is associated with a substantially increased risk of all-cause dementia and Alzheimer’s disease.

The associations were strong but these studies didn’t find a direct causal link between vitamin D deficiency and the onset of dementia.

The research so far has fallen short in persuading doctors and health authorities to routinely prescribe vitamin D as a protection.

“It’s too early to recommend increasing your daily dose of vitamin D in hopes of preventing dementia or Alzheimer’s disease,” the Mayo Clinic advises.

But this may soon change – because a world-firststudy from the University of South Australia (UniSA) “shows a direct link between dementia and a lack of vitamin D”.

It also found that nearly one in five cases might be prevented with a vitamin D intervention.

The main findings

Using neuro-imaging and a tool that measures gene variation, the study found:

Low levels of vitamin D were associated with lower brain volumes and an increased risk of dementia and stroke

Genetic analyses supported a causal effect of vitamin D deficiency and dementia

In some populations as much as 17 per cent (nearly one in five) of dementia cases might be prevented by increasing everyone to normal levels of vitamin D (50 nmol/L).

According to an explainer from the University of South Australia, the genetic study analysed 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 stroke.