The enzyme lactase is responsible for breaking down lactose which is a sugar in milk. The enzyme is located on the folds in the wall of the small intestine. People who are gluten intolerant have an immune response that results in destruction of the folds. They frequently become lactose intolerant. A common finding in lactose intolerance is diarrhoea. Why does this occur? Lactose is a disaccharide that is broken down to the monosaccharides glucose and galactose for absorption. People who have structural changes in the intestine due to gluten intolerance have decreased lactase and therefore decreased ability to digeste lactose. If the undigested lactose remains in the faeces it exerts an osmotic effect that prevents water reabsorption in the intestine. Because increased amounts of water remain in the faeces it is unformed and we know this as diarrhoea.