About Lactase Persistence

What is lactase persistence?

Lactase persistence is a genetic trait that affects the body's ability to digest dairy products.

Lactose (with an "o") is a sugar found in human, cow and goat milk. Lactase (with an "a") is an enzyme that helps digest lactose. The body makes more lactase during early childhood when babies generally drink lots of milk containing lactose. After this time, the amount of lactase begins to decline and is at very low levels by age 10.

https://www.mayoclinic.org//-/media/kcms/gbs/patient-consumer/images/2017/12/04/14/31/lactasepersistence-main-1240x720.jpg People with low levels of lactase are lactase non-persistent. They have difficulty digesting dairy products, also known as lactose intolerance, beyond childhood. Symptoms of lactose intolerance can include bloating and abdominal pain, nausea, gas and diarrhea. https://www.mayoclinic.org//-/media/kcms/gbs/patient-consumer/images/2017/12/04/14/31/lactasepersistence-main2-1240x720.jpg However, people with lactase persistence can easily digest milk products throughout their lifetime. Lactase persistence is a good thing if you consume dairy products.

What gene is associated with lactase persistence?

Lactase persistence is an inherited trait caused by variants in the MCM6 gene located on chromosome 2. https://www.mayoclinic.org//-/media/kcms/gbs/patient-consumer/images/2017/12/04/14/31/lactase-chromosomes.png

What role do genetic factors play in the likelihood of lactase persistence?

Lactase persistence is passed down from parents to children in an autosomal dominant pattern. Click here to learn about autosomal dominant inheritance.

Lactase activity is controlled by genes. The LCT gene directs cells to make the enzyme lactase. But another gene, MCM6, controls or turns off the LCT gene late in childhood when milk is no longer the main source of nourishment. One or more variants of MCM6 cause the LCT gene to stay on and to continue to produce lactase into adulthood.

What role do non-genetic (environmental) factors play in lactase persistence?

Some people who have health problems such as celiac or Crohn's disease also have symptoms of lactose intolerance for reasons other than genetic variants in MCM6. This is called secondary lactose intolerance.

For more information about secondary lactose intolerance

How does ethnicity affect lactase persistence?

The likelihood that you have lactase persistence depends on your ethnicity.

Percent of United States population with lactase persistence - 61-67%

The percentage of people worldwide who have lactase persistence varies widely depending on whether or not dairy products were historically important in their diet:

Africa
Uganda- 6-20%
Sudan- 47-63%

Asia
India- 36-42%
China- 14-18%

Europe
Ireland- 92-100%
Hungary- 59-64%
Greece- 61-68%
Italy- 26-29%

Middle East
Iran- 2-12%
Saudi Arabia- 69-75%

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Additional lactase persistence resources

Mayoclinic.org: Lactose intolerance Genetics Home Reference: Lactase persistence