Evidence check: FUT2 in the context of sleep

The link between FUT2 (secretor status) and sleep is indirect and mechanistic. FUT2 variants such as rs601338 affect intestinal B12 absorption. B12 deficiency can theoretically impair sleep via homocysteine elevation and altered neurotransmitter synthesis (e.g., melatonin, serotonin). However, no direct human studies associate FUT2 genotypes with sleep quality, duration, or disorders. The evidence is purely mechanistic, extrapolated from B12-sleep research. A DNA test for FUT2 alone cannot predict your sleep. If deficiency is suspected, measure serum B12 first. The effect size of FUT2 on B12 is modest; many non-secretors have normal levels. Marketing often overstates genetic prediction. Conclusion: No clinically actionable sleep insight from FUT2 testing.