Lactose intolerance is the body’s inability to breakdown lactose, the predominant sugar in milk. This inability results from a shortage of the enzyme lactase, which is produced by the cells that line the small intestine. Lactase breaks down lactose into simpler sugars that can then be absorbed into the bloodstream. When there is not enough lactase to digest the lactose, the results, although not usually dangerous, may be very distressing. While not all persons deficient in lactase have symptoms, those who do are considered to be lactose intolerant.
Common symptoms include nausea, cramps, bloating, gas, and diarrhea, which begin about 30 minutes to 2 hours after eating or drinking foods containing lactose. The severity of symptoms varies depending on the amount of lactose each individual can tolerate.
Some causes of lactose intolerance are known. For instance, certain digestive diseases and injuries to the small intestine can reduce the amount of enzymes produced. In rare cases, children are born without the ability to produce lactase. For most people, though, lactase deficiency is a condition that develops naturally over time. After about 2 years of age, the body begins to produce less lactase. However, many people may not experience symptoms until they are much older.
Between 40 and 60 million Americans suffer from lactose intolerance. Certain ethnic and racial populations are more widely affected than others. Lactose intolerance affects approximately 75% of all African Americans and American Indians and 90% of Asian Americans. The condition is least common among persons of northern European descent. Researchers have identified a genetic variation associated with lactose intolerance; this discovery may be useful in developing a diagnostic test to identify people with this condition.
The most common tests used to measure the absorption of lactose in the digestive system are the lactose tolerance test, the hydrogen breath test, and the stool acidity test. These tests are performed on an outpatient basis at a hospital, clinic, or doctor's office. The lactose tolerance and hydrogen breath tests are not given to infants and very young children who are suspected of having lactose intolerance. Both these tests require the consumption of lactose which may be dangerous for the very young because they are more prone to dehydration that can result from diarrhea caused by lactose. If a baby or young child is experiencing symptoms of lactose intolerance, many pediatricians simply recommend changing from cow's milk to soy formula and waiting for symptoms to subside.
Fortunately, lactose intolerance is relatively easy to treat. No treatment can improve the body's ability to produce lactase, but symptoms can be controlled through diet. Dietary control of lactose intolerance depends on people learning through trial and error how much lactose they can handle. Young children with lactose intolerance should not eat any foods containing lactose. Some older children and adults may not have to avoid lactose completely, but people differ in the amounts and types of foods they can handle.
BALANCED NUTRITION WITHOUT DAIRY PRODUCTS
Milk and other dairy products are a major source of nutrients in the American diet. The most important of these nutrients is calcium. Calcium is essential for the growth and repair of bones throughout life. In the middle and later years, a shortage of calcium may lead to thin, fragile bones that break easily, a condition called osteoporosis. A concern for both children and adults with lactose intolerance is getting enough calcium in a diet that includes little or no milk.
In planning meals, it is important to make sure that each day's diet includes enough calcium even if the diet does not contain dairy products. Many non-dairy foods are high in calcium. Green vegetables such as broccoli and kale, and fish with soft, edible bones, such as salmon and sardines, are excellent sources of calcium. To help in planning a high-calcium and low-lactose diet, the table that follows (Table 2) lists some common foods that are good sources of dietary calcium and shows how much lactose they contain.
Even though lactose intolerance is widespread, it need not pose a serious threat to good health. People who have trouble digesting lactose can find quality dairy-free alternatives readily available that replace their dairy counterparts. Older women at risk for osteoporosis and growing children who must avoid milk and foods made with milk can meet most of their special dietary needs by eating greens, fish, and other calcium-rich foods that are free of lactose. A carefully chosen diet, with calcium supplements if the doctor or dietitian recommends them, is the key to reducing symptoms and protecting future health.
1. “Lactose Intolerance.” National Digestive Diseases Information Clearinghouse (NDDIC). 28 Feb 2005. National Institutes of Health (NIH).
2. “Lactose Intolerance.” The American Gastroenterological Association. 22 Feb. 2005.