Myths vs facts: LCT and sleep

The claim that the LCT gene (lactase persistence) directly affects sleep is a myth. LCT determines whether lactose can be digested in adulthood – not sleep quality. A common myth is that dairy products promote sleep due to tryptophan, but this effect is independent of LCT genotype. In fact, individuals with lactose intolerance (LCT non-persistence) may experience digestive discomfort from dairy before bed, which can disrupt sleep. The evidence for a direct LCT-sleep link is weak; no robust studies show a causal relationship. For sleep issues, focus on general sleep hygiene rather than LCT genotype. Bottom line: LCT is a marker for lactose digestion, not sleep. Evidence is unclear due to lack of specific studies.