Although lactose intolerance in adults is a common disorder and occurs in approximately 65 percent of the world's population, congenital lactose intolerance is extremely rare. It is more prevalent in the Finnish population, where it affects 1 in 60,000 newborns. Due to a genetic disorder, babies with congenital lactose intolerance are unable to digest the carbohydrate present in milk from the time they are born. In contrast to congenital lactose intolerance, people with primary lactose intolerance lose the ability to digest milk as they age.
Lactose Digestion
Because carbohydrates can only be absorbed in their simplest form, lactose, a disaccharide in milk, needs to be broken into its monosaccharide units. Digestion of lactose requires the action of lactase, an enzyme produced in the small intestine. Lactase splits lactose into its building block units of galactose and glucose, which are then absorbed in the small intestine. In children with congenital lactose intolerance, the intestinal cells cannot produce lactase, so they are unable to digest breast milk or infant formula containing lactose.
Cause of Congenital Lactose Intolerance
Congenital lactose intolerance or congenital lactase deficiency is an autosomal recessive disorder, and is only prevalent if an infant inherits defective genes from both parents. Due to mutations in the lactase gene, newborn babies with congenital lactose intolerance are unable to produce the enzyme lactase, and therefore, are unable to digest lactose in their mother's milk or in infant formula. Undigested lactose passes on into the colon, where the intestinal bacteria break it down. The resulting gastrointestinal disorder, characterized by watery diarrhea, can be severe if not diagnosed and treated immediately.
Symptoms and Treatment
Symptoms of congenital lactose intolerance in the first few days of life are frequent bouts of diarrhea after the infant feeds on mother's milk or lactose-containing formula. The baby's life is at risk because of the danger of dehydration, acidosis and weight loss. The only treatment is replacing lactose-containing milk with infant formula that is free of lactose. Since this is a lifelong condition, children with this genetic disorder cannot drink regular milk or eat products that contain milk.
Cause of Primary and Secondary Lactose Intolerance
Your body adapts to decreased milk intake by decreasing the amount of lactase produced by the intestinal cells. According to the International Foundation for Functional Gastrointestinal Disorders, this natural response to the varied diet you consume starts between the ages of 3 to 5 years, and is the main cause of primary lactose intolerance in adults. On the other hand, secondary lactose intolerance occurs due to surgery of the small intestine or an illness of the gastrointestinal tract, which may decrease lactase production and make you lactose intolerant.
References
- National Institutes of Health: Genetics Home Reference: Lactose Intolerance
- International Foundation for Functional Gastrointestinal Disorders: Lactose Intolerance: Definition, Symptoms and Treatment
- MayoClinic.com; Lactose Intolerance; February 2010
- National Digestive Diseases Information Clearinghouse (NDDIC); Lactose Intolerance; June 2009
