Updated: Oct 14, 2020
Lactose Intolerance is the small intestine’s inability to fully digest lactose, a sugar contained in milk/dairy products. The disorder is a common digestive issue and while typically harmless, its symptoms can be very uncomfortable.
Symptoms often include intestinal bloating and cramps, nausea, flatulence, and diarrhea.
When your body doesn’t have enough of the enzyme lactase, produced in the small intestine, this often results in lactose intolerance. Even low levels of lactase will allow you to digest milk products. But if your levels are too low you become lactose intolerant, leading to symptoms after you eat or drink dairy products.
Lactose, the main sugar found in milk and other dairy products, is broken down by the enzyme lactase, which is produced by the cells in the inner lining of the small intestine. Lactase separates lactose into two parts, glucose and galactose. These simple sugars get absorbed into the bloodstream. Without lactase, lactose cannot be digested or absorbed.
If you're lactase deficient, lactose passes into the colon instead of being broken down and absorbed. In the colon, bacteria interact with undigested lactose, producing the signs and symptoms of lactose intolerance.
Lactase levels are high in infants, allowing them to digest milk. However, in some ethnic groups, lactase levels decrease after weaning. These decreased levels result in older children and adults in these ethnic groups being unable to digest lactose. However, most people of Northwest European descent produce lactase into adulthood and are thus able to digest dairy products for life.
Temporary lactose intolerance can develop when the lining of the small intestine is damaged by a disorder, such as an autoimmune disease or intestinal infection. After recovery from these disorders, most people are able to digest lactose again.