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Cause of Lactose Intolerance

A shortage of an enzyme called lactase is the cause of lactose intolerance. There are two categories of lactase deficiency: primary lactase deficiency and secondary lactase deficiency. Either one of these deficiencies can be the cause of lactose intolerance. Risk factors, such as being a certain ethnicity or being born prematurely, can increase a person's chance of having lactose intolerance.

 

An Introduction to the Cause of Lactose Intolerance

Lactose intolerance is caused by a shortage of the enzyme lactase (lactase deficiency).
 
Some causes of lactase deficiency are well known; in other cases, research scientists are not sure why a person develops this deficiency.
 
There are two general categories of lactase deficiency:
 
  • Primary lactase deficiency
  • Secondary lactase deficiency.
     
Not all people with lactase deficiency have the symptoms commonly associated with lactose intolerance, but those who do are said to have lactose intolerance.
 

Cause of Lactose Intolerance: 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 lactose intolerance symptoms until they are much older.
 

Cause of Lactose Intolerance: 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:
 
(Cause of Lactose Intolerance Continued: Page 2)
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Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD