Sarcopenia and Vitamin B12: Where Do We Stand?

Background/Objectives: Sarcopenia is an age-related skeletal muscle disorder associated with functional decline, frailty, and reduced quality of life. Vitamin B12 plays an essential role in neuromuscular function, DNA synthesis, and homocysteine metabolism, yet its relationship with sarcopenia remains incompletely understood. This narrative review aimed to summarize the current evidence regarding the association between vitamin B12 status and sarcopenia and to discuss the potential biological mechanisms underlying this relationship. Methods: A literature search was conducted in PubMed, Scopus, and Web of Science to identify relevant studies published up to 4 September 2026. Twenty studies met the eligibility criteria and were included in this narrative review. Evidence regarding muscle mass, muscle strength, physical performance, and the biological mechanisms linking vitamin B12 to sarcopenia was synthesized narratively. Results: The included studies reported heterogeneous findings regarding the association between vitamin B12 status and sarcopenia-related outcomes. Some studies suggested that adequate vitamin B12 status was associated with better muscle mass and physical performance, whereas others found no independent association after adjustment for potential confounding factors. Vitamin B12 deficiency has been linked to neuromuscular dysfunction, hyperhomocysteinemia, and impaired muscle metabolism, providing biological plausibility for a potential association. However, findings regarding muscle strength and the overall association with sarcopenia remained inconsistent across studies, reflecting differences in study populations, diagnostic criteria, and methodological approaches. Conclusions: Current evidence suggests heterogeneous and, in some cases, subgroup-specific associations between vitamin B12-related measures and selected sarcopenia-related outcomes. However, methodological heterogeneity, the predominantly observational nature of the evidence, and potential residual confounding preclude causal inferences and do not allow a reliable determination of which individual components of sarcopenia are most consistently associated with vitamin B12.