Normally upon the consumption of lactose, it is hydrolyzed by the intestinal brush-border enzyme, lactase, into absorbable sugars, namely glucose and galactose. Lactase is found in the small intestine and localized to the tips of the villi, a factor of clinical importance when considering the effect of diarrheal illness on the ability to tolerate milk.
Deficiency of lactase due to primary or secondary causes results in clinical symptoms. Lactase nonpersistence results in incomplete digestion of an ingested load of lactose; hence lactose is malabsorbed and reaches the colon. If sufficient lactose enters the colon, the subject may experience symptoms of abdominal pain, bloating, excess flatulence, and diarrhea, a condition known as lactose intolerance
There are 4 main causes of lactase deficiency:
*Primary Lactase Deficiency
It is the most common cause of lactase deficiency, also known as lactose nonpersistence. There is a gradual decline in lactase enzyme activity with increasing age. Most people will not notice symptoms until they are much older.
*Secondary Lactase Deficiency
Secondary Lactase Deficiency occurs when injury to intestinal mucosa due to several infectious, inflammatory or other diseases can cause secondary lactase deficiency. These diseases include celiac disease, inflammatory bowel disease, and Crohn’s disease.
*Congenital Lactase Deficiency
Some people are born with a likelihood of developing primary lactase deficiency because it has been passed to them genetically.
*Developmental Lactase Deficiency
It is seen in premature infants born at 28 to 37 weeks of gestation. The intestine of the infant is underdeveloped resulting in an inability to hydrolyze lactose.
Common symptoms, which range from mild to severe, include nausea, cramps, bloating, gas, and diarrhea. Symptoms begin about 30 minutes to 2 hours after eating or drinking foods containing lactose.
Lactose Intolerance
