When you have only enough energy to walk to the refrigerator, it's hard to top a hunk of cheese, a cup of yogurt or a glass of milk as easy, nutritious foods-if you can digest them. But for the 80 percent of the world's population that is lactose-intolerant, milk can cause cramping, gas, bloating, nausea and diarrhea. PWAs can be at special risk, but a range of alternatives is readily available to quench that thirst for a glass of chilled milk.

Lactose is a complex sugar found in virtually all dairy products. To be digested, it must be broken down into simpler components by the enzyme lactase. Without this enzyme, lactose ferments in the bowel, causing digestive distress.

As young mammals are weaned, the production of lactase declines sharply, and milk becomes difficult or impossible to digest. Some people, however, who have downed a glass of milk daily since infancy have prolonged their body's ability to produce lactase and are able to digest milk easily. In effect, these people have never been weaned. Many others have only partially sustained this ability and are lactose-intolerant in different degrees. Inborn lactose intolerance varies by ethnic background and region. An estimated 75 percent of African-Americans and Native Americans, as well as 90 percent of Asians, are moderately to severely lactose-intolerant, while Northern Europeans tend to have the least difficulty-probably because of evolutionary changes due to generations of dietary patterns. However, the presence of HIV seems to induce lactose intolerance-even in those with no prior history-because HIV interferes with gastrointestinal processes. The National Institutes of Health describes most people living with AIDS as lactose-intolerant. Another complication: Beyond the discomfort caused by nausea, gas, cramps and bloating, diarrhea is a critical and all-too-common problem in people with HIV. Sustained diarrhea can cause lactose intolerance (either permanent or reversible), just as lactose intolerance can cause diarrhea-a vicious cycle that can lead to dehydration and foster wasting.

Lactose levels in dairy foods differ. Many, but not all, people who cannot drink milk can eat cheese. As a rule, the higher the butterfat content, the lower the lactose level. So some people can eat premium (high-butterfat) brands of ice cream, but not generic brands. In dairy products such as yogurt or cheese, the fermentation process has worked much like lactase to break down the lactose into a form the body can assimilate. Sweet acidophilus milk is fermented with a nonsour strain of yogurt bacteria, providing both lowered lactose and "friendly flora" to the gut. Firm cheeses, such as cheddar or parmesan, which have undergone the most thorough processes of fermentation, have very little lactose.

How to determine if you are lactose-intolerant? Although there are medical tests (hydrogen breath test, stool acidity test and lactose-absorption blood test), this is easily determined at home by completely avoiding dairy for two or three days and then drinking a glass of milk. If any of the described symptoms appear within the next two hours, chances are you are lactose-intolerant.  The intensity of the symptoms will indicate the severity of your intolerance. A milk allergy (usually in reaction to one of the proteins found in milk) is different from lactose intolerance and is typically characterized by skin rashes and respiratory problems.

If you are lactose-intolerant, you have several options. You can supplement lactase with such products as Lact-Aid, Dairy Ease or their generic counterparts. Product lines now include lactose-free milk and ice cream. Only trial and error can determine if they help you.

Alternatively, you can switch to soy milk, rice milk, almond milk or oat milk, especially as a substitute for dairy milk in your morning cereal. Such products as Eden Soy, Vita Soy, Rice Dream, Silk Rice Milk or Mill Milk Organic Oat Milk work well for many people and taste better than you might think.

Either way, you will want to read ingredient labels carefully; milk byproducts (which contain lactose) are hidden in places you would not expect, such as some margarine brands. Look for the words milk, lactose, whey, curds, milk byproducts, dry milk solids, nonfat dry milk powder or lactic acid. For those severely intolerant, be mindful that 20 percent of prescription drugs and 6 percent of over-the-counter drugs are compounded with lactose (your pharmacist can advise you about specific medications). Products labeled with the kosher term pareve contain no dairy products.

So, if you are HIV positive, don't raid the fridge for a piece of pie a la mode without knowing your lactose status first.