Now, I think it's time to look at the number-one reason for poor health: digestive problems. And to focus on an aspect of digestion that's often ignored – lactose in tolerance. If you're lactose intolerant, you may have had increased digestive disturbances during the holiday season.

Many of us tend to go off our dietary programs, at least to some degree, between Thanksgiving and New Year's. If these changes have resulted in your eating more dairy – such as desserts, creamed soups, and pumpkin pie – you may have been more bloated. Or perhaps you had unexplained diarrhea or abdominal pain. If so, your increased dairy consumption could be to blame. Eating more dairy can lead to lactose intolerance.

What is lactose, and why does it bother us?
Lactose is a sugar found naturally in milk and other dairy products. To digest it, your body needs to make an enzyme called lactase. Lactase helps you digest lactose. But if you're over the age of five, your body may be making very little lactase. Seventy-five percent of the world's population stops producing lactase after being weaned. That's almost everyone! This is nature's way of telling us we don't need to drink milk to be healthy. If you can't digest lactose, you're considered to be lactose intolerant. Lactose intolerance is an enzyme deficiency – not a true allergy. It increases as we age and our enzyme production decreases.

Basics of lactose intolerance
You need the enzyme lactase to digest the milk sugar lactose. If you don't have enough lactase, lactose can't be digested and get into your bloodstream. Instead, it remains in your intestines. The lactose in your intestines attracts water, which leads to bloating. When lactose makes its way into your large intestines (colon), intestinal bacteria eat this undigested sugar creating gas and acid. The gas and acid produce cramps, more gas, and, frequently, diarrhea.

If you get any of these symptoms, either immediately or for up to 12 hours after eating dairy, you may be lactose intolerant. Specific tests can confirm or rule out a lactose-digesting problem.

Testing for lactose intolerance
Lactose challenge test: Stop using all dairy except for butter for two weeks. Read the labels of all foods carefully. If any foods contain milk solids or are creamy, they may contain dairy. Some creamed soups available in health food stores contain no dairy. Otherwise, most creamed foods in supermarkets do. To test yourself for a lactose problem, remove dairy completely for two full weeks. If you are lactose intolerant, you should notice fewer digestive problems. At the end of two weeks, drink a little milk or eat some ice cream. Wait up to half a day and see what happens. If you have no digestive problems, try eating more dairy the following day. Still feel fine? Chances are you don't have a problem with lactose. Feel more bloated? Dairy is likely the culprit.

Brenda Davis, RD, in her book Dairy-Free & Delicious, mentions other tests your doctor can do to determine lactose intolerance. These are helpful if you don't have the willpower to stop eating all dairy for two weeks. Sometimes it’s easier to change your lifestyle when a laboratory test indicates there’s a problem.