Everything you need to know about lactose intolerance

Woman with stomach pain holding a glass of milk

What is Lactose?

Lactose, the sugar found in dairy products, is digested by the lactase enzyme. Lactase is produced in the small intestine and is responsible for breaking down lactose into two smaller and more readily absorbable sugars – glucose and galactose.

Most mammals produce high levels of the lactase enzyme as infants, and then lactase production decreases after weaning. However, due to our reliance on dairy products as a food source, many humans now have lactase persistence, where the lactase enzyme is continually produced throughout adulthood. These lactase persistent individuals can continue to digest lactose throughout their lifetime.

Lactase persistence occurs in more than 75% of Caucasians around the world, and approximately 95% of people of Northern European ancestry. Other ethnicities have a much lower proportion of lactase persistence (e.g. approximately 50% of Mexicans, only 10% of Asians and less than 5% of Native Americans). 

What is Lactose Intolerance?

Lactose intolerance occurs due to decreased production of the lactase enzyme. Undigested lactose builds up in the large intestine, resulting in the growth of gas-producing gut bacteria, which contribute to the symptoms of lactose intolerance, including bloating, flatulence, diarrhea, nausea and abdominal pain. This may be a temporary lactase reduction (e.g. after surgery or short-term illness) or a permanent reduction, due to a lifelong disease (e.g. cystic fibrosis) or due to genetic variation.

Our DNA Lactose Intolerance Test identifies individuals that carry a genetic variation that permanently reduces lactase production.

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Lactose intolerance differs from a dairy allergy, as individuals who are allergic to dairy will have an immune response (an allergic reaction) against milk proteins, whereas lactose intolerance is a digestive disorder.

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