Vitamin D insufficiency is common in the United States; the elderly and African-Americans are at particularly high risk of deficiency. This review, written for a broad scientific readership, presents a critical overview of scientific evidence relevant to a possible causal relationship between vitamin D deficiency and adverse cognitive or behavioural effects. Topics discussed are 1) biological functions of vitamin D relevant to cognition and behaviour; 2) studies in humans and rodents that directly examine effects of vitamin D inadequacy on cognition or behaviour; and 3) immunomodulatory activity of vitamin D relative to the proinflammatory cytokine theory of cognitive/behavioural dysfunction. We conclude there is ample biological evidence to suggest an important role for vitamin D in brain development and function. However, direct effects of vitamin D inadequacy on cognition/behaviour in human or rodent systems appear to be subtle, and in our opinion, the current experimental evidence base does not yet fully satisfy causal criteria. Possible explanations for the apparent inconsistency between results of biological and cognitive/behavioural experiments, as well as suggested areas for further research are discussed. Despite residual uncertainty, recommendations for vitamin D supplementation of at-risk groups, including nursing infants, the elderly, and African-Americans appear warranted to ensure adequacy.
McCann JC, Ames BN. Is there convincing biological or behavioural evidence linking vitamin D deficiency to brain dysfunction? FASEB J. 2008 Apr;22(4):982-1001. Epub 2007 Dec 4. View Abstract View Full paper