digestive disorders
Lactose Intolerance
Causes of Lactose Intolerance
Lactaselevels are high in infants, permitting them to digest milk. However, in most ethnic groups (80% of Black people and Hispanic people, more than 90% of Asian people),lactaselevels decrease after weaning. These decreased levels mean that older children and adults in these ethnic groups are unable to digest much lactose. However, 80 to 85% of White people of Northwest European descent producelactasethroughout life and are thus able to digest milk and milk products as adults. Therefore, because of the ethnic composition of the United States' population, it is likely that between 30 million and 50 million people in the United States are lactose intolerant. It is interesting that this "intolerance" is really the normal state for more than 75% of the world’s population. Temporary lactose intolerance can develop when a disorder, such as an intestinal infection (see Overview of Gastroenteritis ), damages the lining of the small intestine. Once people recover from these disorders, they are able to digest lactose again. Intolerances to other sugars can also occur but are relatively rare. For example, a lack of the enzyme sucrase prevents the sugar sucrose from being broken down and absorbed into the bloodstream, and a lack of the enzymes maltase and isomaltase prevents the sugar maltose from being broken down and absorbed into the bloodstream. 