Lactose malabsorption is a common condition caused by reduced expression or activity of lactase in the small intestine. Lactose is the sugar found in dairy products such as milk and other dairy foods. Intolerance to lactose typically lead to symptoms such as gas, bloating, diarrhea or cramping when dairy products are digested. These symptoms are a result of the body's lack of lactase, an enzyme normally produced by the small intestine that is needed to digest lactose.
The most frequent cause of lactose malabsorption is lactase non-persistence, a common condition in which lactase expression decreases during infancy. Lactase malabsorption is associated with conditions including small bowel bacterial overgrowth, infectious enteritis (i.e. giardiasis), or mucosal damage due to coeliac disease, inflammatory bowel disease or gastrointestinal syrgery, which cause the absorptive capacity of the small intestine, as well as downregulation of lactase expression in the small intestine.
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