Fall in Canada may be pretty, but daylight, a natural source of vitamin D, is on the wane. We know light deficiency can alter our moods (hello again, seasonal affective disorder), but now researchers say they’ve found a link between vitamin D deficiency and dementia risk. In a study published in the August issue of the American Journal of Clinical Nutrition, the authors reported that 33,000 U.K. participants aged 37 to 73, who had a genetically higher level of vitamin D – blood concentrations of over 50 nanomoles per litre (nmol/l), an amount considered sufficient to maintain healthy bones – had a decreased dementia risk, “with the odds of dementia decreasing with higher … concentrations.” In this group, the researchers observed that up to 17 per cent of dementia cases might have been avoided by boosting vitamin D levels to a normal range. But modifications to diet may not be enough, and supplementation may be needed. According to a 2013 report from Statistics Canada, 34 per cent of the population took a supplement containing vitamin D; 85 per cent of those pill poppers were above the 50 nmol/l cutoff compared with 59 per cent of nonsupplement users. For those under 70, Health Canada’s recommended dietary allowance (RDA) for vitamin D is 600 IU (15 micrograms), while the RDA increases to 800 IU (20 mcg) for people over the age of 70. If you’re not already taking the sunshine vitamin, ask your doctor to check your levels to see if supplements are right for you.