ASK THE DOCTOR: Lactose troubles can be treated
By Dr. JIM MITTERANDO
The Patriot Ledger

Q. I have problems with cramping and diarrhea when I eat dairy products. Is lactose intolerance a food allergy?

A. Lactose intolerance is the diminished ability to digest a sugar called lactose that is present in milk and dairy products. Normally when you eat something containing lactose, the small intestine produces an enzyme called lactase. Lactase breaks down lactose into simpler sugars that can be absorbed into the bloodstream. People with lactose intolerance do not produce as much lactase enzyme. This causes undigested lactose to remain in the digestive tract causing gas, stomach cramps, and diarrhea.

Not a food allergy

Milk allergy and lactose intolerance are frequently confused but they are not the same thing. A food allergy is a reaction of the immune system to proteins in food that can cause rashes, dry skin or anaphylaxis (a life-threatening reaction that results in wheezing and low blood pressure).

Food intolerance is the inability to digest a particular food; it is not life-threatening but rather a nuisance. Milk allergy tends to occur during infancy whereas lactose intolerance tends to occur later in life and affects older children and adults. Allergy-causing foods need to be completely avoided whereas people with food intolerance can control their symptoms by the limiting the amount of the food consumed.

Some people who believe they are lactose intolerant actually do not have impaired lactose digestion but may have other problems such as irritable bowel syndrome (where the digestive tract is overly sensitive to things such as stress or low-fiber foods).

Evaluation for lactose intolerance

The best way to determine if dairy products are causing your symptoms is to try an ‘‘elimination diet'' that excludes dairy foods for one to two weeks. During this time keep a log of how often you have symptoms. Then reintroduce the food and see if the symptoms recur. If they recur, you can try various amounts of dairy to see what you can tolerate. If the symptoms continue then you should see your doctor. Testing for lactose intolerance is rarely done since it mostly diagnosed and treated by dietary changes. Testing may rarely be needed in severe or unclear situations.

Intolerance varies

Lactase deficiency and lactose intolerance aren't the same. In fact, some people without much of the milk-digesting enzyme are not bothered by lactose.

People differ in the amounts and types of foods they can handle. For example, one person may have symptoms after drinking a small glass of milk, while another can drink one glass but not two.

Lactose intolerance can be a collection of symptoms produced not only by how much lactase is available for digestion but also by the way the digestive system responds and adapts to the undigested milk sugar. A person with a naturally sensitive gut might feel the effects of undigested lactose more. There may be an overlap between lactose intolerance and conditions like irritable bowel syndrome.

Intolerance may also vary with the bacteria living in your colon. If you avoid milk and dairy foods, your colon may lose the bacteria best suited to processing undigested lactose.

Finally, there may be a psychological component. Some people develop strong aversions to dairy food after experiencing mild intolerance symptoms. In experiments, researchers have shown some people who believe they are lactose intolerant can, in fact, digest it without symptoms if they're not told the food contains lactose.

Editor's note: In two weeks, Dr. Mitterando will write about treating lactose intolerance.

Dr. Jim Mitterando is a family doctor at Cohasset Family Practice and a staff member at South Shore Hospital in Weymouth.

Readers should send questions to: Ask the Doctor, The Patriot Ledger, P.O. Box 699159, Quincy, MA 02269-9159, or by E-mail to his attention at features@ledger.com.

Questions of general interest will be answered in this column. The information in this column is not intended to diagnose individual conditions, and individual replies are not possible. Readers should see their own doctors about specific problems.

Copyright 2004 The Patriot Ledger
Transmitted Tuesday, September 14, 2004