If, after drinking a glass of milk, a bowl of cereal or a scoop of ice cream, you suffer stomach upset, bloat, gas or diarrhea, you may be unable to properly digest a sugar called lactose, which is present in milk products. Lactose intolerance is characterized by a deficiency in the enzyme lactase, which is needed to digest milk sugar. A common condition, it affects 50 million people in the United States, according to the 2011 edition of "Current Medical Diagnosis and Treatment." It affects members of some ethnic groups more than others, suggesting that there is a hereditary component.
Lactase Deficiency
Most people are born with a perfect ability to digest mother's milk. But over time, many develop low levels of the enzyme lactase, which is required to break down lactose, or milk sugar, into the simple sugars glucose and fructose. As a result, lactose remains in the digestive tract, serving as food for bacteria. Bacteria of the lactobacilli species, or lactose fermenters, break down lactose into hydrogen and methane. This gives rise to gas, which can be foul smelling.
Genetic Basis
Primary lactase deficiency generally occurs around age 2. At this time, your body begins to produce less of the enzyme. Primary lactase deficiency may have a genetic basis, according the National Digestive Diseases Information Clearinghouse. In other words, if you are lactose intolerant, you likely inherited this gene from one of your parents. Primary lactose intolerance is different from the secondary form, which results from injury to the small intestine, as may occur in severe diarrhea, in conditions such as Crohn's disease or in chemotherapy.
By Population
Supporting the theory that lactose intolerance is hereditary, members of some ethnic groups tend to be more intolerant than members of other groups. In fact, as many as 90 percent of Asian-Americans are lactose intolerant, as are 70 percent of African-Americans. Ninety-five percent of Native Americans are deficient in lactase, while 50 percent of Mexican Americans have difficulty tolerating milk sugar, according to "Current Medical Diagnosis and Treatment." In contrast, less than 25 percent of white adults are lactose intolerant.
Treatment
The first step in treating lactose intolerance is to eliminate milk products from your diet. This usually relieves symptoms. If you find it difficult to say no to milk, try drinking less at a time, as people with low lactase levels can drink up to 4 oz. of milk without symptoms. Yogurt, cheeses and lactose-free and lactase-treated milk products are other options, as they contain lower levels of the offending sugar.
References
- "Current Medical Diagnosis and Treatment"; Stephen J. McPhee; 2011
- PubMed Health: Lactose Intolerance
- National Digestive Diseases Information Clearing House: Lactose Intolerance
- MayoClinic.com: Lactose Intolerance
- "Biochemistry"; Pamela C. Champe, Ph.D.; 2005
