What is lactose intolerance?

Causes and Symptoms

Lactose is a complex sugar commonly found in dairy products. It is composed of two simple sugars, glucose and galactose. In babies and young children, a gene produces an enzyme called lactase that breaks down lactose into its two component sugars, which are then absorbed into the bloodstream through the intestinal wall. In many people, sometime after early childhood, the lactase gene is “turned off.” It no longer synthesizes lactase, which prevents the digestion and absorption of lactose.

Normal bacterial inhabitants of the intestines synthesize lactase and break down the lactose molecules, producing large quantities of gas as a by-product. This can lead to cramping for the lactose-intolerant individual. The presence of lactose in the large intestine causes excessive amounts of water to move into the intestine, which can lead to diarrhea. Symptoms subside one to two days after the last lactose-containing food has been consumed.

Treatment and Therapy

Lactose intolerance can often be misdiagnosed as a host of gastrointestinal disorders, largely as a result of the commonness of its major symptoms, cramps and diarrhea. Typically, a dietary history must be kept. Patients with lactose intolerance will note an association between their symptoms and the consumption of milk products containing lactose. After elimination of these products from the diet, symptoms should not recur.

There is no cure for lactose intolerance; prevention of symptoms is the general course of action. Avoidance of foods that contain lactose—including milk, ice cream, and cheese—is usually the best recourse. For those who wish to indulge in these products, over-the-counter lactase pills are available; their use usually prevents symptoms of the disorder.

Perspective and Prospects

The vast majority of the world’s population is lactose intolerant, yet this disorder was not recognized until later in the twentieth century. Today, lactase supplements are available to help prevent symptoms for lactose-intolerant people who choose to consume dairy products. Alternatively, more and more dairy products are being manufactured as lactose-free; they can be consumed safely by the lactose-intolerant population.

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