Vitamin D intake from food may prevent or improve cognitive function

In this large population-based study recently published in Neurology, researchers highlight a growing interest in the literature exploring the role of vitamin D as a neurosteroid hormone in the nervous system, and its influence in cognitive function and/or neurodysfunction.   Investigators note current research suggests that vitamin D supplementation may be especially helpful to deficient elderly patients, possibly maintaining or improving global cognitive function.  Because no randomized controlled trials have tested this possibility, the authors of this study suggested that before conducting a supplement drug trial it is important to first assess whether vitamin D from food – and not supplements - could be associated with cognitive performance in the elderly. 

Annweiler C. et al “hypothesized that high dietary intake of vitamin D could protect against cognitive decline.”  They tested their hypothesis among two groups of older women participating in the Epide´miologie de l’Oste´oporose (EPIDOS) cohort.  A total of 5,596 women participated, divided into two groups based on their baseline weekly vitamin D intake from food (inadequate < 35 ug/wk & recommended ≥ 35 ug/wk).  Intake was estimated based on a food frequency questionnaire, and cognitive impairment was scored via a validated mental state questionnaire.  Sun exposure, season, depression, education, age and many other potential confounders were considered in the statistical analysis.  Notably, women were excluded from the study if they consumed vitamin D supplements in the previous 18 months.

Ruling out potential confounders, the central finding of this study was that weekly vitamin D intake from food sources was significantly associated with overall cognitive performance; women with inadequate dietary intakes of vitamin D had a greater prevalence of cognitive impairment.  Among several explanations the authors discuss, one explanation of the observed associations between vitamin D intake and cognitive decline may have to do with the nature of food.  Citing two other studies, they write, “Nutrition indeed integrates complex interactive effects of many dietary constituents. Nutrients are not consumed in isolation but rather as components of an overall diet, which is precisely considered as a modifiable risk factor for cognitive decline.” 

In order to establish causality and accurately determine mechanisms of action Annweiler C. et al encourage prospective nutrition studies and clinical trials “to assess a direct effect of vitamin D intake on cognitive decline.”

Study: Annweiler, C. et al Neurology, 75; 1810-16 (2010)