Milk is an excellent source of bone-building calcium and other important nutrients — but for some folks, it's also a source of gastrointestinal misery. As many as 70 million Americans are believed to suffer from lactose intolerance, a condition that renders them unable to properly digest the sugar in milk and other dairy products.
The primary sugar in milk is lactose — a large, bulky molecule comprised of two simpler sugars, glucose and galactose. Before lactose can be absorbed through the walls of the intestine and converted into energy to be used by the body, it must first be cleaved into its smaller constituents.
Splitting the milk sugar lactose is a relatively simple digestive process, but it requires a specific enzyme, known as lactase, which is produced by the cells lining the small intestine. Most healthy, full-term infants make plenty of the enzyme, and as a result, they're able to thrive on a steady diet of milk or milk-based formula.
After the age of two, however, lactase production typically begins to decline. Individuals who don't make enough lactase to break down the sugar in the milk and dairy products they consume are considered to be lactose intolerant.
Lactase production is a genetically programmed process, and to a large degree, the development of lactose intolerance is influenced by a person's heritage. While the condition is less common among people of Northern European decent, approximately 80 percent of Asian Americans, African Americans and Native Americans are believed to be lactose intolerant.
If your body doesn't produce enough lactase, most of the sugar from milk and other dairy products you consume travels through the digestive tract, largely intact. The undigested milk sugar draws fluid into the bowel, contributing to cramping and diarrhea.
Gastrointestinal discomfort may not be the worst aspect of lactose intolerance, at least as far as your social life is concerned. Bacteria in the gut devour the undigested milk sugar, shamelessly producing copious quantities of intestinal gas in the process. Once the gas makes its inevitable exit, it can make you very unpopular with the people around you.
Symptoms of lactose intolerance, which range from mild to severe, can begin within 15 minutes of eating dairy products, or they may take several hours to develop. Surprisingly, many people with the condition aren't aware that they have it, especially if they don't associate their intestinal fireworks with the consumption of milk or dairy foods.
How do you know if you have lactose intolerance? While a number of high-tech diagnostic tests are available, the least expensive way to diagnose the condition is to adopt a lactose-free diet for a week or two.
If adding dairy products back to your diet leads to cramping, diarrhea or excessive gas, it's probably safe to say that you're lactose intolerant. Still, it's wise to discuss your symptoms with your physician to rule out other, more serious problems.
The good news is that in spite of your condition, you may not have to swear off dairy products altogether. Since lactose intolerance affects individuals in varying degrees, there's a good chance that you can still enjoy some of your favorite dairy delicacies. With a little experimentation, you can determine which foods you can tolerate and which ones cause your gastrointestinal tract to rebel.
You may find that you can enjoy a small glass of milk or two each day, especially if you drink it with meals. Consuming milk in modest quantities and with other foods increases the chances that it will be properly digested.
If you still experience gastrointestinal distress, you might get relief by taking supplemental lactase. Sold over the counter, lactase supplements work just like the natural enzyme to facilitate proper digestion of the milk sugar in dairy products.
If you're like most folks with lactose intolerance, you'll probably find that you can still enjoy aged cheeses, including Swiss and extra-sharp cheddar, as these foods have only traces of lactose. Because yogurt contains helpful bacteria that have already begun the process of lactose digestion, you may be able to eat it without experiencing any digestive disturbance.
If you'd rather steer clear of lactose altogether, you can find lactose-reduced and lactose-free milk and dairy foods at most supermarkets. Although these products may be slightly more expensive, they generally contain all the nutrients found in regular dairy products.
Lactose intolerance doesn't have to make you miserable. With a little extra care, you can still enjoy eating a few of your favorite dairy foods, symptom free.
Rallie McAllister is a board-certified family physician, speaker and the author of several books, including "Healthy Lunchbox: The Working Mom's Guide to Keeping You and Your Kids Trim."
Copyright 2009 Creators Syndicate, Inc.