Vitamin B₁₂, folate, and Alzheimer's disease

Abstract

Vitamin B₁₂ and folate have been suspected to be involved in the etiopathogenesis of dementia and Alzheimer's disease (AD) for years, as a deficiency of either vitamin may produce severe neurological consequences, including confusion and memory loss. This review briefly summarizes the major studies published in the literature concerning vitamin B₁₂, folate, and AD. Using a number of study designs and exposure assessments, findings from studies conducted from different countries suggest that vitamin B₁₂ deficiency/low level is more often found in AD patients than nondemented persons. The results of folate in relation to AD have been inconsistent. Generally, population-based studies indicate that folate deficiency/low level is not only related to AD but also all types of dementia. Results from studies on the combination of the two vitamins suggest that vitamin B₁₂ and folate may be equally important in the etiology of AD. The null findings from some of the studies may have resulted from the differences in study design, population, control selections, as well as methods of exposure assessment and cut-offs chosen. It may be premature to reach any conclusions at the moment based on the limited studies available, especially the lack of prospective studies and randomized clinical trials. Studies conducted up to the present suggest that deficiency / low level of vitamin B₁₂ and folate may be of etiological importance for AD. Drug Dev. Res. 56:111–122, 2002. © 2002 Wiley-Liss, Inc.