Final answer:
Lactose intolerance is caused by insufficient lactase enzyme production, leading to undigested lactose that produces gas, bloating, and diarrhea after fermentation by bacteria in the large intestine. Treatments include a lactose-free diet or enzyme supplements.
Step-by-step explanation:
The underlying cause of problems a lactose intolerant person experiences when they consume lactose is the insufficient production of lactase, an enzyme that digests lactose. Without adequate lactase, lactose remains undigested and passes into the large intestine, where bacteria ferment it, leading to the production of gas and other symptoms like bloating, diarrhea, and abdominal cramps. The symptoms are a direct result of this fermentation process and the inability to break down lactose.
Lactose intolerance typically develops in adulthood, though it can appear in children as well. It's more common in some populations, such as those of Asian descent. Treatments include avoiding lactose-containing foods, using lactose-free dairy products, or taking lactase enzyme supplements.
In more severe cases, a genetic disorder called galactosemia can occur, which is caused by the absence of an enzyme that converts galactose to glucose, leading to symptoms like diarrhea and vomiting when lactose is consumed.