Lactose intolerance is the body's inability to properly digest lactose, a type of sugar that is present in milk, cheese, and other dairy-based items. This is due to a deficiency in lactase, a digestive enzyme present in the small intestine. Some people are affected with lactose intolerance from birth, while others develop the condition later in life. This acquired intolerance may be due to the quality and quantity of the enzyme breaking down, or it may be a secondary response to another digestive problem such as Crohn's disease, ulcerative colitis, or celiac disease. Lactose intolerance varies in intensity, but it can cause bloating, gas, stomach cramps, and diarrhea within two hours of eating or drinking dairy products. A common digestive issue, it has been estimated that 65 percent of the world's population has some form of lactose intolerance.
Testing for lactose intolerance often starts with the patient ingesting dairy products in a clinical setting so the physician can observe the results. Determining if the intolerance is due to enzyme deficiency or an underlying condition, as mentioned above, is also essential. One of the most reliable tests involves measuring the level of hydrogen in a person's breath after drinking a lactose solution. Hydrogen is a byproduct of the bacteria in the digestive system if lactose cannot be processed efficiently.
Blood tests are another way that doctors can determine lactose intolerance. Over a period of hours and several draws, the sugar in the blood—glucose—will rise slowly in patients who are lactose intolerant. The easiest and most accurate test for infants is a stool acidity test; those whose bodies cannot process lactose will have a low pH level in their stools due to the presence of acid.
People who are diagnosed with lactose intolerance often find that avoiding foods with dairy products is the easiest way to manage their condition. Lactase replacement medication is also available over-the-counter; these supplements can be taken just before consuming a meal with dairy products to temporarily colonize the digestive system with lactase enzymes.