Evidence Level
Vitamin B12 deficiency is more prevalent than previously recognized, with Wolffenbuttel et al. (2019) documenting that 6% of those under 60 and up to 20% of those over 60 are deficient across multiple population studies. The consequences of deficiency are well-established: megaloblastic anemia, neurological damage, and elevated homocysteine. A 2018 meta-analysis by Martí-Carvajal et al. confirmed that B-vitamin supplementation (including B12) significantly reduces homocysteine levels, though the impact on cardiovascular event reduction requires further study. For cognitive outcomes, Moore et al. (2012) found consistent associations between low B12 status and accelerated cognitive decline, and the VITACOG trial demonstrated that B-vitamin supplementation slowed brain atrophy by 30% in elderly subjects with elevated homocysteine.