lactose and tolerant

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 secondary LI is generally caused by a nutritional problem or a sickness that results in a person\'s inability to digest lactose. At birth, virtually all humans have lactase enzymes, and thus the ability to digest lactose. As people age, some of them lose lactase enzymes. The age when people start to lose lactase and the amount finally retained differ greatly, so people are affected by LI in varying degrees. Some people have virtually no tolerance to dairy products at all, while others are affected only mildly. People with zero tolerance levels normally must completely avoid milk products. Most lactose intolerant people, however, can tolerate differing amounts of lactose in their diets, depending on their lactase deficiency.

The three predominant methods of determining if a person is lactose intolerant are known as the lactose challenge test, the blood sugar test and the hydrogen breath test (Englert and Guillory 904). In all three of these tests the patient is given a known quantity of lactose (normally the amount found in one quart of milk), called a lactose load. In the lactose challenge test the effects of the lactose load such as cramping, gas and diarrhea are then carefully monitored. If a person has these LI symptoms, he or she is presumed to be lactose intolerant. In the blood sugar test, blood sugar levels are monitored through blood samples after the consumption of the lactose load. If the sugar level does not rise to a prescribed level, the patient is determined to be lactose intolerant because if the lactose had been digested the blood sugar level would have risen. In the hydrogen breath test the hydrogen level of the breath is monitored after ingestion of the lactose load. Higher than normal hydrogen levels will appear in the breath if the lactose is not digested because undigested lactose is fermented in the colon. Fermentation releases hydrogen which is absorbed into the blood and ultimately exhaled through the lungs. Once a person is determined to be lactose intolerant, the level of LI can be determined through careful evaluation of lactose intake in various foods. By finding the threshold of lactose susceptibility, lactose intolerant people can tailor their diets to match that threshold. These people can then consume milk products up to their threshold with little or no lactose related problems.

Although dairy products are the predominant source of lactose in our diet, there are many other non-dairy sources. Lactose is a