Vitamin B12 (Cobalamin) is an essential water-soluble vitamin that serves as a cofactor for two critical enzymatic reactions: methionine synthase (involved in the methylation cycle and homocysteine regulation) and methylmalonyl-CoA mutase (involved in branched-chain amino acid and fatty acid catabolism). B12 is essential for maintaining myelin sheath integrity, neurological function, and DNA synthesis. Research at high parenteral doses explores its role in neuroprotection, fatigue, cognitive support, and recovery from deficiency states. It is a cornerstone component of many longevity and vitality-focused peptide protocols.