Myths vs facts: LCT and Schlaf

The relationship between LCT (lactase persistence) and sleep is often surrounded by myths. A common myth is that dairy products before bed promote sleep due to tryptophan content. In reality, evidence for a direct sleep-enhancing effect of milk is weak and highly individual. Another myth is that lactose intolerance causes sleep disturbances. The fact is: LCT gene variants determine the ability to digest lactose. In lactose intolerant individuals, dairy consumption can lead to bloating, abdominal pain, and diarrhea, which may indirectly disrupt sleep. However, there are no robust studies showing a direct genetic link between LCT variants and sleep quality or duration. Most sleep issues are multifactorial. A DNA test for LCT can inform about lactose tolerance, but not about sleep. The evidence level is mechanistic/practice-based, not strong clinical evidence. Caution is advised against exaggerated claims from direct-to-consumer tests.