Galactose is a simple sugar that is a component of lactose, the sugar found in milk and dairy products. Upon ingestion, lactose is broken down into glucose and galactose by the enzyme lactase. In individuals with galactosemia, the enzyme galactose-1-phosphate uridyltransferase (GALT) is deficient or absent, leading to an accumulation of galactose-1-phosphate and other toxic metabolites in the body.
