Diagnosing Lactose Intolerance
If your morning glass of milk regularly gives you gas, chances are you have lactose intolerance, says Sheila Crowe, MD, an associate professor of internal medicine at the Digestive Health Center of Excellence at the University of Virginia in Charlottesville. Shared by as many as 50 million Americans, according to the National Institutes of Health, this diagnosis means you can't digest significant amounts of lactose, the predominant sugar in milk. A shortage of the enzyme lactase in your body is to blame.
While its most prominent symptom is gas, a lactase deficiency may also be marked by diarrhea, nausea, cramps, and bloating, which set in about 30 minutes to two hours after eating or drinking lactose-laden foods. Whether you're uncomfortable or in distress will depend on whether you consumed just a bite or an entire double scoop of Ben & Jerry's -- and how much lactose your system can take.
While digestive diseases may disrupt production of lactase, lactose intolerance generally develops naturally over time. At about two years of age, your body starts to produce less of the enzyme. What's more, certain ethnic and racial populations are more widely affected than others. In fact, as many as 75 percent of all African-Americans and American Indians, and 90 percent of Asian-Americans can't break down the sugar.
A visit to your doctor's office can confirm whether you have a lactase deficiency. Your physician may inquire about your symptoms and request you keep a food journal to record your reactions to certain foods, says Dr. Crowe. Or, he or she may administer one of three easy tests:
- For the lactose intolerance test, blood sugar levels are taken before and after you drink a liquid containing lactose. If you digest the lactose normally, your blood sugar level should rise. If it doesn't, you are deficient in lactase.
- The hydrogen breath test determines the amount of hydrogen in your breath. After drinking a lactose-containing beverage, your breath is analyzed over the next several hours. Normal hydrogen levels are low; high levels indicate lactose intolerance.
- A stool acidity test is used for infants and very young children for whom consuming large amounts of lactose can be dangerous (it can spur dehydrating diarrhea). The test can determine how much acid and glucose are in the stool; their presence will indicate if you have undigested or unabsorbed lactose.