Lactose Intolerance: Another Painful Reason For Growing Up Lactose intolerance (LI) is the inability of some humans to digest the lactose sugar contained in most dairy products and foods made with dairy products. LI has numerous readily apparent physical symptoms such as gas, cramps and diarrhea (Houts 110). More importantly, LI may lead to malnutrition in those people affected because of the loss of milk's important nutrients. Not everyone is affected by LI. In fact, genetic background rather than any other health or cultural factor seems to best predict LI. The inability of humans to digest lactose has enormous health consequences, particularly among the poor populations of the U.S. and the developing third-world countries. LI was first recognized in the 1960s when researchers found black children responding unfavorably to milk in their diets (Harrison 812). Research led to the discovery that lactose, the major sugar in milk and related dairy products, was undigestible in some people because they were missing the enzyme lactase. Lactase breaks down lactose into its component monosaccharide sugars, glucose and galactose. In people missing lactase, lactose passes undigested through the small intestine. In some people, the undigested lactose passes through the remainder of their systems with no ill effects. In others, however, the undigested lactose becomes viscous and ferments in the colon (Englert and Guillory 903). The thickness of the liquid and the fermentation cause painful cramping, gas and sometimes diarrhea. Besides not being able to digest lactose, these people suffer from malabsorption, which causes them to receive little or none of milk's nutrients (Houts 110).1 The two major classes of LI are primary and secondary; both have the same ultimate symptoms and cause the same problems (Englert and Guillory 903, Houts 110). Primary LI is the natural loss of lactose tolerance from birth because of the loss of lactase, while secon...
