Lactose Intolerance: Overview


What is lactose intolerance? 

The Digestive Health Institute tests for lactose intolerance
Lactose intolerance is the inability to fully digest lactose, which is the main type of sugar that is found in milk and dairy products.

What causes lactose intolerance? 

As people get older, we gradually lose the ability to digest lactose. Lactose cannot be absorbed by the intestines and used in the body unless it is digested. Lactase is the enzyme in our intestinal wall which digests lactose into two smaller sugar particles that are then easily absorbed. 

As we age, lactase production decreases and in some individuals, this leads to lactose intolerance. When lactose is not digested and travels through the intestinal tract, it can lead to the development of symptoms like diarrhea. Undigested lactose is consumed by the bacteria that live normally in our large intestine leading to gas production. 

Who gets lactose intolerance?

Lactose intolerance is extremely rare in infants and young children, who are born with sufficient lactase to digest milk sugar. In older children, adolescents, and adults, however, lactose intolerance is a common problem. The frequency of lactose intolerance varies by race and ethnicity, with the lowest occurrence in European Americans and higher occurrence in African Americans, Hispanic Americans, Asian Americans and Native Americans.

Helpful resources

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