Evidence check: LCT in the context of Darmgesundheit

The LCT gene encodes lactase, the enzyme that breaks down lactose (milk sugar). Variants in its regulatory region (e.g., rs4988235) determine whether lactase production persists into adulthood (lactase persistence) or declines (lactase non-persistence). In non-persistence, consuming dairy can cause bloating, diarrhea, and abdominal pain – directly affecting gut health. The evidence is human-strong: numerous GWAS, clinical trials, and population genetics studies confirm this link. However, lactose intolerance is just one piece of the puzzle; gut health involves microbiome composition, inflammation, barrier function, and more. A genetic test for LCT can provide useful dietary guidance but should not replace medical evaluation for persistent symptoms. The effect size is substantial for lactose digestion but moderate for overall gut health.