The MCM6 gene controls the Lactase producing gene (LCT). Lactase is necessary to digest the sugar Lactose found in milk. Individuals whose body cannot produce Lactase are described as Lactose Intolerant (unable to digest Lactose in milk).
Specific versions of this gene are known to either increase or decrease likelihood for lactose intolerance. People with the TT variant of the gene can produce Lactase throughout their lifetime whereas people with the CC variant stop producing Lactase beyond late childhood.
Lactase breaks down lactose, a naturally occurring sugar found in dairy products. The level of lactase expressed in the small intestine gradually declines in infants after they are weaned, with the result that most individuals lose the ability to digest lactose in adulthood. When lactose is digested well, it is broken down into two sugar molecules, glucose and galactose. When it is not digested well, it results in the undigested lactose being acted upon by gut bacteria that ferment the lactose, producing gas, and leading to abdominal bloating and cramps. These are some of the symptoms associated with lactose intolerance.
A study conducted by The Sanjay Gandhi Post Graduate Institute of Medical Sciences showed that the CC variant was found in 86.8% of South Indians and 67.5% of North Indians. This correlated with the lactose intolerance test conducted, which was found to be abnormal for 88% of the South Indian volunteers and 66% of the North Indian volunteers.
[Advantage] More Likely to be Lactose Tolerant
[Limitation] More Likely to be Lactose Intolerant