Lactose intolerance is the inability or insufficient ability to digest lactose, a sugar found in milk and milk products. Lactose intolerance is caused by a deficiency of the enzyme lactase, which is produced by the cells lining the small intestine. Lactase breaks down lactose into two simpler forms of sugar called glucose and galactose, which are then absorbed into the bloodstream as glucose.
Lactose intolerance is commonly seen among infants. Studies show that 50% of adult Asian population also show intolerance to lactose. In infants it is often due to a congenital error of metabolism due to the deficiency of the enzyme ?-galactosidase. Lack of lactase also leads to it.
Growth retardation is seen in children. Clinical features seen in others include –
Distention and bloating
Stools with lactose and lactic acid
Retention of undigested disaccharides in the intestines increases the osmotic load of the intra-luminal contents and cause an excess quantity of fluid to be drawn into the intestine in order to dilute the sugar concentration. This leads to an increase in motility of the intestines and causes cramps, bloating and diarrhoea. The undigested sugars are fermented by the bacteria in the colon leading to the formation of lactic acid. The lactic acid is excreted in the stools and this irritates the bowels leading to diarrhoea. The fermentation results in excessive carbon dioxide production leading to bloating of the stomach.