Digestive System Home > Cause of Lactose Intolerance
A shortage of an enzyme called lactase is the main cause of lactose intolerance. There are two categories of lactase deficiency: primary lactase deficiency and secondary lactase deficiency. Either one of these deficiencies can lead to lactose intolerance. Risk factors, such as being Asian American or being born prematurely, can increase a person's chance of having the condition.
Lactose intolerance is caused by a shortage of the enzyme lactase. This is known as a lactase deficiency.
Some causes of lactase deficiency are well known; in other cases, research scientists are not sure why a person develops this condition.
There are two general categories of lactase deficiency:
- Primary lactase deficiency
- Secondary lactase deficiency.
Not all people with the condition have lactose intolerance symptoms.
Primary Lactase Deficiency
In rare cases, a child is born without the ability to make lactase. However, most cases of primary lactase deficiency develop over time. In these cases, for unknown reasons, the body begins to produce less lactase after about the age of two. Most people will not notice symptoms until they are much older.
Secondary Lactase Deficiency
Secondary lactase deficiency occurs when the amount of lactase a person produces is reduced by some injury to the small intestine. This type of deficiency can also be caused by certain digestive diseases. The diseases that can cause secondary lactase deficiency include:
While not a lactose intolerance "cause," certain risk factors can make some people more likely to develop the condition. A risk factor is anything that increases a person's chance of developing a disease. Specific risk factors for lactose intolerance include:
- Ethnicity: African Americans, American Indians, and Asian Americans are more likely to be lactose-intolerant.
- Premature birth: Babies that are born prematurely are more likely to be lactose-intolerant because lactase levels do not increase until the third trimester of a woman's pregnancy.
Not everyone with known risk factors will have lactose intolerance. In addition, many who do get the condition have none of these risk factors.