Tekkadan/USDT 🌐 on Nostr: In humans, lactase is encoded by a single genetic locus on chromosome 2. It is ...

In humans, lactase is encoded by a single genetic locus on chromosome 2. It is expressed exclusively by mammalian small intestine enterocytes and in very low levels in the colon during fetal development. Humans are born with high levels of lactase expression. In most of the world's population, lactase transcription is down-regulated after weaning, resulting in diminished lactase expression in the small intestine, which causes the common symptoms of adult-type hypolactasia, or lactose intolerance. The LCT gene provides the instructions for making lactase. Lactose intolerance in infants (congenital lactase deficiency) is caused by mutations in the LCT gene. Mutations are believed to interfere with the function of lactase, causing affected infants to have a severely impaired ability to digest lactose in breast milk or formula.

Some population segments exhibit lactase persistence resulting from a mutation that is postulated to have occurred 5,000–10,000 years ago, coinciding with the rise of cattle domestication. This mutation has allowed almost half of the world's population to metabolize lactose without symptoms.

Lactase is added to milk, thereby hydrolyzing the lactose in the milk, leaving it slightly sweet but digestible by everyone. Without lactase, lactose-intolerant people pass the lactose undigested to the colon where bacteria break it down, creating carbon dioxide which leads to bloating and flatulence.