Myths vs facts: B12 and sleep

The claim that vitamin B12 directly improves sleep is a common myth, often based on anecdotal reports or animal studies. In reality, the evidence for a sleep-promoting effect of B12 in humans is weak. B12 is essential for nerve myelination and neurotransmitter synthesis (e.g., serotonin, melatonin), but deficiency primarily causes fatigue and neurological symptoms, not specific sleep disorders. Some observational studies link low B12 levels to insomnia or delayed sleep phase, but these are associations, not causal. Supplementation in individuals with normal levels does not provide proven sleep benefits. The evidence is 'human-moderate': there are hints but no robust RCTs to support general use. For sleep issues, focus on sleep hygiene, light exposure, and stress reduction rather than B12 supplements.