If you suffer bloating, gas and diarrhea after drinking milk, blame it on lack of lactase (the intestinal enzyme that is necessary to break down the milk sugar lactose). For most people this condition is genetically determined. It is most common among Eastern European, African, Asian, South American and Native American populations. For example, only about 20 percent of Caucasians are lactose intolerant, compared with 75 percent of African-Americans and 90 percent of Asian-Americans. Lactose intolerance also can occur if the intestinal wall is damaged from disease or malnutrition.
Milk and other dairy foods contain the disaccharide lactose. During digestion, an enzyme in the intestines called lactase breaks down the milk sugar lactose into two simpler molecules (glucose and galactose) that are then absorbed and used by the body. People who are lactose intolerant don't produce enough lactase and therefore cannot completely digest the lactose in milk, resulting in symptoms of bloating, gas and, at times, diarrhea. Two separate actions work to cause the familiar symptoms: 1) The intact lactose molecule attracts excess water into the small intestines, causing bloating; and 2) when the undigested lactose reaches the colon, intestinal bacteria begin to digest the unabsorbed lactose, producing gas and diarrhea.
Except for a rare congenital form of alactasia, everyone is born with the ability to digest lactose — healthy infants grow normally on human milk or formula, both containing lactose, for many months. But after early childhood, levels of lactase in the body begin to decrease, leaving adults with this genetic predisposition with inadequate levels of the enzyme to digest normally consumed levels of lactose-containing products.
The degree of lactose intolerance can vary between individuals. Some people may be unable to digest even the smallest amounts of milk, while others may experience symptoms only after drinking larger-than-usual quantities. People who believe they are lactose intolerant often avoid all dairy foods to save themselves potential discomfort. Moreover, nondairy foods may contain lactose that is added during processing. When eliminating lactose from the diet, it is important to review the contents of prepared and processed foods to determine if they are lactose-free.
Here are some tips about which dairy products are easier to digest and ways to cope with lactose intolerance:
- Yogurt, which is made of fermented milk products, is usually well tolerated.
- Acidophilus milk contains the harmless bacteria Lactobacillus acidophilus, which breaks down the lactose for you.
- Cottage cheese is usually well tolerated, since the part of the cheese that contains the most lactose, the whey, is removed during manufacturing.
- Hard and aged cheeses are also well tolerated. The amount of lactose in a cheese decreases as the cheese ages.
- Lactose-free milk (such as Lactaid) is usually available at the grocery store.
- Use lactase enzyme pills or drops if needed.
If you are concerned about not getting enough calcium in your diet, healthy sources of nondairy calcium include canned salmon and sardines, calcium-fortified orange juice, tofu, spinach and kale. Or take a calcium supplement such as calcium carbonate, 500 milligrams once or twice a day. Also be certain to get an adequate amount of vitamin D daily, especially if you spend most of your time indoors (sunlight activates vitamin D in your skin).
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