What is Lactose Intolerance?
Lactose intolerance is caused by the body's inability to digest milk sugar, or lactose. In order to break lactose down into simple sugars, or monosaccharides, the body must produce the enzyme called lactase, which is produced in the small intestine. Without lactase, the lactose from milk products is unabsorbed and ferments in the intestine. This causes the symptoms of gas, cramps, and diarrhea that many people experience after eating or drinking dairy products.
Lactose intolerance is a condition that normally develops over time. After about 2 years of age, the body begins to produce less of the enzyme lactase. The reasons for this are not understood. Rarely an infant will be born lactose intolerant (LI), which can cause vomiting and 'failure to thrive.' Symptoms of lactose intolerance can appear years after childhood.
Who gets LI, and why?
Experts estimate that as many as 50 million American adults are lactose intolerant (LI). LI is the world's most common disorder, primarily affecting people of Chinese, Korean, Japanese, Jewish, and African descent. People of northern European and some Middle Eastern (Bedouins, Saudis, Yemenis) descents have little incidence of LI. Geographical regions seem to play a role in the incidence of LI. Descendents of people from northern Europe, for example, have been dependent on milk products as a food source in their geographic region for a few thousand years. Those with higher percentages of LI adults have not been dependent on milk products in the geographic regions of their ancestors.
What are the symptoms of LI?
Symptoms of LI can include gas, diarrhea, bloating, cramps, nausea, and very bad breath. These symptoms can begin anywhere from 30 minutes to 2 hours after digesting lactose, and can last for up to 3 days after. The severity of symptoms varies from person to person and is dependent upon the amount of lactose that can be tolerated.
What does LI have to do with Inflammatory Bowel Disease?
Given that LI is the world's most common disorder, it follows that many people with Inflammatory Bowel Disease (IBD) also suffer from LI. The symptoms of gas, bloating, and diarrhea caused by IBD are compounded by the same symptoms caused by LI.
How is LI diagnosed?
There are three tests most commonly used to diagnose LI, the lactose intolerance test, the hydrogen breath test, and the stool acidity test.
The lactose intolerance test. This test is appropriate for both older children and adults. Patients will fast for several hours before the test begins. Blood is drawn to measure the current blood glucose level. Next the patient will drink a liquid that contains up to 50 grams of lactose. For the next two hours more blood samples are taken to measure blood glucose levels. If the lactose is being broken down by the enzyme lactase, the blood glucose level will rise. If the blood glucose level does not rise, that means that the lactose is not being broken down into simple sugars, and the patient is lactose intolerant.
The hydrogen breath test. This test is very similar to the lactose intolerance test, and might be done on children as young as 6 months as well as adults. After fasting for several hours, the patient will exhale into a mouthpiece connected to a foil bag that looks like a balloon. This bag is to be used as a comparison for the second part of the test. Next the patient will drink a liquid that can contain up to 50 grams of lactose. More breath samples will be taken at various intervals for up to 6 hours.
Normally, there is no hydrogen present in a person's breath. When a lactose intolerant person ingests lactose, it stays in their intestines and ferments, ultimately producing hydrogen gas. Therefore, if hydrogen is present in the breath samples taken after drinking the lactose, the diagnosis of lactose intolerance can be made.
The stool acidity test. This test is normally done on small children, as it is non-invasive, and presents no problems, such as dehydration caused by diarrhea, from ingesting large amounts of lactose. A stool sample is collected and tested for lactic acid, glucose, and other short-chain fatty acids that may be present when lactose remains undigested by the body.
