Lactose is a large sugar molecule that is made up of two smaller sugar molecules, glucose and galactose. In order for lactose to be absorbed from the intestine and into the body, it must first be split into glucose and galactose. The glucose and galactose are then absorbed by the cells lining the small intestine.
In the milk of most mammals, lactose is generally the major carbohydrate, so when you have a glass of milk, and it gets through your stomach to the small intestine, that lactose gets chopped into glucose and galactose by an enzyme that’s fittingly called lactase.
If lactase is deficient, nondigested lactose is not absorbed. The nonabsorbed lactose keeps on movin’ down the GI tract and passes into the colon.At this point, the gut flora has a field day, since microbes aren’t as picky and they ferment the lactose into a mix of hydrogen gas, carbon dioxide, and methane. These gases contribute to symptoms of gas and bloating.
Along with those gases, though, short-chain fatty acids are produced like acetate, butyrate, and propionate. We don’t absorb these short-chain fatty acids, which means that they stay in the lumen of the gut.
Both the unabsorbed lactose and products of fermentation raise the osmotic pressure, attracting water into the bowels, so water flows in and this influx of water is what leads to diarrhea.
There are two types of lactase deficiency.
First one is congenital lactase deficiency, caused by a mutation in the gene encoding lactase, which is an autosomal recessive disorder. The disease is rare and presents as explosive diarrhea with watery, frothy stools and abdominal distention upon milk ingestion. Symptoms abate when
exposure to milk and milk products is terminated.
Second one is acquired lactase deficiency is caused by down- regulation of lactase gene expression. Acquired lactase deficiency can develop following enteric viral or bacterial infections and may resolve over time.
Dietary management is the primary form of treatment for lactose intolerance. Patient is advised to reduce or restrict lactose containing food such as milk. Recently commercially available lactase enzymes are also used to reduce symptoms.
