Folate and vitamin B12: function and importance in cognitive development

The importance of the B vitamins folate and vitamin B12 for healthy neurological development and function is unquestioned. Folate and vitamin B12 are required for biological methylation and DNA synthesis. Vitamin B12 also participates in the mitochondrial catabolism of odd-chain fatty acids and some amino acids. Inborn errors of their metabolism and severe nutritional deficiencies cause serious neurological and hematological pathology. Poor folate and vitamin B12 status short of clinical deficiency is associated with increased risk of cognitive impairment, depression, Alzheimer's disease and stroke among older adults and increased risk of neural tube defects among children born to mothers with low folate status. Folate supplementation and food fortification are known to reduce incident neural tube defects, and B vitamin supplementation may have cognitive benefit in older adults. Less is known about folate and vitamin B12 requirements for optimal brain development and long-term cognitive health in newborns, children and adolescents. While increasing suboptimal nutritional status has observed benefits, the long-term effects of high folate intake are uncertain. Several observations of unfavorable health indicators in children and adults exposed to high folic acid intake make it imperative to achieve a more precise definition of folate and B12 requirements for brain development and function.