Lactose intolerance is the inability to digest lactose, the main sugar contained in milk products.
KEYWORDS
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Galactose
Glucose
Lactase
Metabolism
Erin's Story
Erin's favorite food had been ice cream since her first birthday. On her thirteenth birthday, the rocky road sundae with hot fudge went down without a hitch, but an hour later she felt awful. She had cramps and diarrhea * , and, even more embarrassing, gas. Erin's friend, whose mother had the same reaction to milk products, explained that she probably was becoming lactose intolerant, meaning that she could not digest all of the natural sugar in the ice cream.
What Is Lactose Intolerance?
Lactose intolerance refers to the inability of the small intestine to break down the sugar lactose (LAK-tos) because of a lack of or too little of the enzyme * lactase (LAK-tays). Lactose is a complex sugar found in milk products. Normally, when lactose reaches the small intestine, it is broken down into the simple sugars glucose (GLOO-kose) and galactose (ga-LAK-toz) by a protein, or enzyme, called lactase. Simple sugars can be absorbed easily through the wall of the small intestine into the blood-stream, but larger, more complex sugars like lactose cannot. If someone is lactose intolerant, that person's intestine does not make enough lactase, or the lactase it does make does not work properly.
If lactose is not broken down, it absorbs water, so that the water cannot pass through the intestinal wall into the bloodstream. This extra fluid remaining in the bowel causes diarrhea. Also, bacteria (microorganisms) in the digestive tract convert lactose to lactic (LAK-tik) acid in a process called fermentation (fur-men-TAY-shun). Fermentation causes bowel movements to be acidic and burn, and it also causes gas, bloating, and cramps. Lactose intolerance is not dangerous, but it is uncomfortable.
* diarrhea (dy-a-RE-a) is abnormally frequent and watery bowel movements.
* enzyme (EN-zim) is a natural sub-stance that speeds up a specific chemical reaction in the body.
Who Becomes Lactose Intolerant?
Doctors estimate that 30 to 50 million people in the United States are lactose intolerant. Up to 75 percent of people of African, Mexican, and Native American ancestry develop lactose intolerance, as do 90 percent of people of Asian ancestry. People of other ancestry are affected less by the problem.
Many people develop lactose intolerance as they get older, because the ability to make lactase decreases with aging. Digestive diseases and injuries to the small intestine also can cause lactose intolerance. Occasionally, children are born without the ability to make lactase.
How Is Lactose Intolerance Diagnosed?
Doctors use three tests to diagnose lactose intolerance. After a person eats or drinks something containing lactose, the doctor can:
Test for a low level of glucose in the bloodstream, which would show that lactose was not broken down properly and absorbed (lactose intolerance test)
Test for a lot of hydrogen in exhaled breath, a sign that bacteria are fermenting lactose (hydrogen breath test)
Test for acidic bowel movements, also a sign that fermentation is occurring (stool acidity test); usually used to test infants and small children
Living with Lactose Intolerance
Symptoms vary from person to person and depend on the amount of lactose eaten. Trial and error helps people learn what not to eat or how much they can eat without becoming ill. Avoiding milk products should eliminate symptoms of lactose intolerance, but people on such a diet must get calcium and vitamin D from other sources. Nonprescription products containing lactase are available that can be taken along with milk products and help the body break down lactose.
Nondairy Sources of
Lactose
Milk, cheese, butter, and ice cream are obvious sources of lactose, but did you know that lactose often is added to the following items?
Baked goods, including bread, and mixes for baked goods
Instant breakfast drinks, potatoes, and soups
Lunch meats
Margarine
Nonfat dry milk powder
Powdered coffee creamer
Many prescription drugs
Processed breakfast cereal
Salad dressing
Many snack foods
Whey
Whipped toppings
Lactose intolerance usually can be managed by following simple strategies:
Drink milk in small servings: 1 cup or less per serving.
Eat cheeses that are low in lactose, such as cheddar.
Only drink milk with meals or other foods.
Eat active-culture yogurts, which contain less lactose than other dairy products.
Use low-lactose or lactose-free milk.
Take lactase enzyme tablets before consuming dairy products, or add lactase enzyme drops to regular milk.
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