How are B12 and longevity related?

The relationship between vitamin B12 and longevity is not clearly established in the scientific literature. B12 is crucial for DNA synthesis, methylation, and energy metabolism—processes linked to aging. Deficiency can lead to cognitive decline, anemia, and neuropathy, impairing healthspan. However, no robust randomized trials show that B12 supplementation at adequate levels extends lifespan. Evidence is mostly observational, associating low B12 status with higher mortality or accelerated aging. Direct-to-consumer DNA tests for B12-related genes (e.g., MTHFR, FUT2) have small effect sizes and do not replace blood testing. For longevity, B12 is one factor among many; a balanced diet with B12-rich foods or supplementation for confirmed deficiency is prudent, but not a proven anti-aging intervention. Safety note: very high doses (e.g., >1000 µg/day) are generally harmless but unnecessary. Evidence grade: unclear.