The Role of B Vitamins in Preventing and Treating Cognitive Impairment and Decline

Abstract

Many epidemiologic studies have considered whether markers of B-vitamin status are associated with cognitive function and cognitive decline. This avenue of research was sparked by the homocysteine (Hcy) theory of cardiovascular disease, which was extended to Alzheimer's disease when a link between vascular dementia and Alzheimer's disease was discovered. Hcy could cause cognitive impairment via direct neurotoxicity. However, decreased remethylation of Hcy to methionine might also compromise cognitive function by means other than mere Hcy lowering. Folate and vitamin B-12 participate in Hcy remethylation and largely determine Hcy status. Consequently, much of the relevant research has focused on these 2 B vitamins. The many subtly different hypotheses that investigators have addressed by attempting to link several B-vitamin status indicators to diverse cognition-related outcomes have created a confusing body of conflicting studies that seems to defy summarization. Nevertheless, themes are discernible that aid interpretation, foster hypothesis generation, and inform future study design. For example, despite a shared metabolic pathway, Hcy, vitamin B-12, and folate are differently related to specific cognitive outcomes. Although consistency of findings across studies is often touted as essential to distinguishing causal from coincidental relationships, discrepancies among study findings can be even more informative.

DTI Correlates of Cognition in Conventional MRI of Normal-Appearing Brain in Patients with Clinical Features of Subacute Combined Degeneration and Biochemically Proven Vitamin B12 Deficiency

“…Sensitive neuropsychological tests have shown an association with vitamin deficiency. 33 In the current study, we also observed a decline in visuospatial and performance skills in these patients. Another group has reported cognitive decline in patients between 35 and 50 years of age with vitamin B 12 deficiency, which improved following its supplementation.…”

Interactions between plasma concentrations of folate and markers of vitamin B12status with cognitive performance in elderly people not exposed to folic acid fortification: the Hordaland Health Study

“…It has been suggested that folate and vitamin B 12 are related to different cognitive outcomes, and that there may even also be a difference in outcomes related to indicators of functional vitamin B 12 status (MMA and holoTC II) v. total concentrations of vitamin B 12 in plasma (43) . A major strength of the present study is the use of an extensive cognitive test battery covering global cognition, perceptual speed, visuospatial skills, episodic memory, access to semantic memory and executive function.…”

Alpha-lipoic acid affects the oxidative stress in various brain structures in mice with methionine and choline deficiency

“…Indirect effect of methionine deficiency may be impaired homocysteine status, which may affect cognitive functions via neurotoxicity. 9 In recent studies, it has been shown that methionine and choline deficiency (MCD), both separately and in combination may induce oxidative stress in various tissues and organs such as liver, kidney, and brain. [10][11][12][13] Alpha-lipoic acid (LA) is well know antioxidant, and has ROS scavenging capacity, the capacity to regenerate endogenous antioxidants such as glutathione, and vitamins E and C, and a metal chelating capacity.…”