Vitamin B12 Intake and Status and Cognitive Function in Elderly People

Current recommendations on vitamin B-12 intake vary from 1.4 to 3.0 mu g per day and are based on the amount needed for maintenance of hematologic status or on the amount needed to compensate obligatory losses. This systematic review evaluates whether the relation between vitamin B-12 intake and cognitive function should be considered for underpinning vitamin B-12 recommendations in the future. The authors summarized dose-response evidence from randomized controlled trials and prospective cohort studies on the relation of vitamin B-12 intake and status with cognitive function in adults and elderly people. Two randomized controlled trials and 6 cohort studies showed no association or inconsistent associations between vitamin B-12 intake and cognitive function. Random-effects meta-analysis showed that serum/plasma vitamin B-12 (50 pmol/L) was not associated with risk of dementia (4 cohort studies), global cognition z scores (4 cohort studies), or memory z scores (4 cohort studies). Although dose-response evidence on sensitive markers of vitamin B-12 status (methylmalonic acid and holotranscobalamin) was scarce, 4 of 5 cohort studies reported significant associations with risk of dementia, Alzheimer's disease, or global cognition. Current evidence on the relation between vitamin B-12 intake or status and cognitive function is not sufficient for consideration in the development of vitamin B-12 recommendations. Further studies should consider the selection of sensitive markers of vitamin B-12 status.