Lactose is milk sugar and is present in whole and skim milk and in all other dairy products. Like most sugars, lactose is broken down by enzymes in the intestinal tract so it can be absorbed as an energy source. The enzyme that breaks down lactose is called lactase. When the intestine does not contain lactase, lactose intolerance can develop. It is a troublesome and annoying problem, but it is never a serious one.

As would be expected, infants and small children have the enzyme lactase so they can digest mothers’ milk. However, during childhood, lactase begins to disappear in many people, the condition is very common.

When undigested lactose reaches the colon (large intestine), it is broken apart by bacteria. Lactic acid and other acidic chemicals result from this break down. It is these products that create the symptoms of lactose intolerance. Symptoms include nausea, abdominal cramps and rumbling, bloating, rectal gas (flatus), and diarrhea. They usually occur 30 minutes to two hours after ingesting lactose-containing foods. The severity of symptoms usually depends on the amount of lactose ingested and how much of the enzyme, lactase, remains in the intestinal tract.

To diagnose Lactose Intolerance, the physician first reviews the patient’s medical history. Sometimes that is enough to determine the problem. However, to make a definitive diagnosis, one of several tests may be needed:

• Lactose Tolerance Test – A test dose of lactose is ingested and blood sugar determinations are made over several hours. If lactase is present to break down the lactose load, then the blood sugar rises. If no lactase is present, the sugar level will not change.
• Hydrogen Breath Test – When lactose is broken down by the colon’s bacteria, hydrogen is released, which then passes out through the lungs. The amount of hydrogen released after a lactose meal can indicate a problem.
• Stool Acidity Test – When lactose breaks down to lactic and other acids in the colon, the resulting acidity can be detected by a simple measurement of stool acidity.
• The At-Home Do-It-Yourself Test – Since lactose intolerance is not a serious disorder, some people may want to test themselves at home. First, avoid milk and lactose-containing foods for several days. Then on a free morning, such as a Saturday, drink two large glasses of skim or low-fat milk (14-16 oz.). Finally, wait. If symptoms develop within four hours, the diagnosis of lactose intolerance is fairly certain.

Therapy depends on how many symptoms the patient can or is willing to tolerate. If your lactose intolerance is mild, then avoiding milk and large amounts of milk products may be enough. For those who are very sensitive to small amounts of lactose, there are two options. First, all foods should be carefully checked for lactose. Grocery items such as bread, baked goods, cereals, instant potatoes, soups, margarine, lunch meat, salad dressings, pancakes, biscuits, cookies, and candy can contain hidden lactose. Even prescription and over-the-counter drugs may contain lactose. The patient must become a label reader looking for and avoiding “milk” and “lactose”.

The second option for severe lactose intolerance is buying milk to which lactase, the enzyme, has been added or adding lactase drops or tablets to milk. A pharmacist or food store manager can provide advice for you. There are over-the-counter lactase tablets that can be taken with meals to replace the enzyme the body no longer has. Finally, there are now a variety of lactose-free products available in the specialty section of food stores.