For some people, nothing is more enjoyable than dipping into a heaping bowl of ice cream. For others, a couple of scoops of ice cream can bring on abdominal cramps, bloating, nausea, vomiting, gas and watery diarrhea within 30 minutes to two hours. The culprit is insufficient production of lactase, the enzyme needed to digest milk sugar (lactose) into its component simple sugars, galactose and glucose.
The condition, known as lactose intolerance, can occur as a rare congenital deficiency. It also can develop secondarily to a bout with the flu or other gastrointestinal disease that damages the lining of the intestine.
Most commonly, however, it occurs as a gradual decline in lactase production with increasing age. The condition has a genetic basis and begins in some ethnic populations as early as age two to three. Because low intestinal lactase in adults is not an abnormal state for at least 75 percent of adults worldwide, lactase nonpersistence has become the recommended term for this type of lactose intolerance. People with lactase production in adulthood are referred to as lactase-persistent individuals. Lactase persistence is more commonly seen in people of Scandinavian, British and Western European descent and nonpersistence in African, Asian, Native American and Mediterranean populations.
Because lactose is found only in milk products, one might conclude that people with lactase nonpersistence must completely avoid milk. This is seldom necessary. Most can enjoy low-lactose dairy products and many can enjoy foods containing some lactose. The degree of tolerance depends on the kind of milk or dairy products that are consumed, the amount that is consumed and other foods that are eaten at the same time.
Many lactase non-persistent people can drink at least one cup of milk without physical discomfort, especially if it is consumed with food. Consuming milk products in smaller amounts in recipes or with meals also reduces the likelihood and/or severity of symptoms. Also, higher-fat milk products, such whole or chocolate milk, are sometimes better tolerated than lower-fat milks because their slower transit rate through the intestine allows more time for the lactose to be broken down.
Aged cheese and yogurt containing live cultures often are well tolerated in moderate amounts by lactase nonpersistent persons. Special low-lactose dairy products, such as LactAid milk, low-lactose cottage cheese and low-lactose ice cream are available. One can also purchase enzymes, such as Dairy Ease, to chew before a meal containing dairy products or to add in liquid or tablet form to milk and other dairy products to pretreat lactose.
Milk and dairy products are not the only products a person with lactose intolerance needs to avoid. Cake mixes, confections, breakfast drinks, hot dogs, bread and a whole host of other processed foods may contain lactose. Terms on labels that indicate the presence of lactose include milk solids, whey, milk byproducts and, of course, lactose. Casein is a milk protein, therefore it does not need to be avoided by people with lactase nonpersistence.
Even some prescription and over-the-counter drugs may contain small amounts of lactose as part of the tablet’s coating, so check the label to be sure. In cases with extreme sensitivity, all products with lactose must be avoided. In other cases, moderation may be all that is needed.
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by Pat Kendall, Ph.D., R.D., Food Science and Human Nutrition Specialist, Colorado State University, Cooperative Extension