Lactose intolerance is the inability to digest significant amounts of lactose, the primary sugar in milk. This inability results from a shortage of the enzyme lactase, which is normally produced by the cells that line the small intestine. Lactase breaks down lactose into glucose and galactose (which changes then into glucose in liver). If this process occurs normally, the glucose enters the bloodstream and raises the blood glucose level.
As many as 75 percent of all adults worldwide and between 30 and 50 million Americans are lactose intolerant meaning they are deficient in the enzyme lactase. Symptoms of lactose intolerance include nausea, bloating, abdominal pain or cramps, abundant gas, and diarrhea. These symptoms usually begin anywhere from 30 minutes to 2 hours after eating a food that contains lactose. Symptoms of lactose intolerance can be uncomfortable enough to temporarily interfere with daily activities, however, they do not harm the digestive system or progress to any other disorder.
There are degrees of intolerance for lactose. Studies have shown that many true lactose intolerants can consume moderate amounts of milk and dairy products without symptoms, particularly if milk is part of a meal. Lactose intolerance cannot be cured. The purpose of the lactose intolerance diet is to bring the symptoms of bloating, gas, abdominal discomfort, and diarrhea under control so that the individual is comfortable, and the symptoms do not disrupt his or her daily activities.
Lactose intolerance is treated by eliminating lactose from the diet beyond the level where it produces symptoms. Although milk and foods made from milk are the only natural sources of lactose, lactose is often added to processed foods, such as bread, cereal, and salad dressing. The greatest risk to this diet is that the individual will not get enough calcium. A dietitian can help the lactose intolerant person develop a meal plan that will meet their dietary need for calcium and/or recommend a calcium supplement.
Many people with lactose intolerance may be able to tolerate yogurt with active cultures, which is very high in calcium, even though it is fairly high in lactose. Evidence shows that the bacterial cultures used in making yogurt produce some of the lactase enzyme required for proper digestion. Lactose-intolerant individuals should also be able to tolerate cheese, as most of the lactose is removed, along with the whey, when the cheese is made.
People with lactose intolerance who do not drink milk can still get the calcium from dark-green, leafy vegetables (broccoli, turnip or collard greens, kale). Certain fish with soft, edible bones, such as herring, salmon, or sardines, are also good calcium sources. Lactose-reduced milk is available at many supermarkets and there are plenty of non-dairy milk alternatives on the market.