Gene LCT
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Also known as
LAC, LPH, lactase, lactase-phlorizin hydrolaseOverview
LCT (Lactase) encodes the enzyme lactase-phlorizin hydrolase, which breaks down lactose (milk sugar) into glucose and galactose in the small intestine. Without sufficient lactase activity, lactose passes undigested into the colon where bacteria ferment it, causing the symptoms of lactose intolerance including bloating, gas, and diarrhea.In most mammal species and most human populations, lactase activity declines after weaning. However, a variant near the LCT gene (MCM6 rs4988235) allows continued lactase production into adulthood, a trait called lactase persistence. This variant arose independently in several populations with dairying traditions and is very common in Northern Europeans but rare in East Asian and African populations.
Understanding your LCT/MCM6 genetic status definitively predicts adult lactase activity and lactose tolerance. This genetic test is more reliable than breath tests for diagnosing lactose intolerance. Individuals with lactase non-persistence can often tolerate fermented dairy products like yogurt and cheese, which have reduced lactose content.