Lactose is a sugar found in milk and milk products, often simply referred to as "milk sugar." It is composed of the simple sugars glucose and galactose, which combine to form the disaccharide lactose. The enzyme lactase, produced by the cells lining the small intestine, breaks down lactose in foods into these simple sugars so they can be absorbed and used for energy in our bodies.
Sources
In general, food sources of lactose include butter, buttermilk, cheese, cottage cheese, cream cheese, all varieties of milk, ice cream, yogurt, sour cream, half-and-half cream and milk chocolate. Check the ingredients on food labels for other sources of lactose, such as whey, curds, milk by-products, dry milk solids and non-fat dry milk powder.
Hidden Lactose
Besides milk and milk products, many other foods contain lactose. These include bread and baked products, waffles, pancakes, biscuits, cookies, processed breakfast foods and cereals, instant potatoes and soup, processed snacks, processed meats, salad dressings, protein powders or bars and candies.
Lactose Levels
The amount of lactose in dairy products varies. Milk contains the highest amounts of lactose, ranging from 11 g per cup of regular milk to a whopping 62 g in one cup of nonfat dry milk powder. Other milks contain between 24 and 40 g of lactose. Enzyme-treated milks have no lactose. Ice cream contains 6 g of lactose in a half-cup serving, while low-fat yogurt contains 5 g per cup. Cottage cheese has about 2 g of lactose per half-cup, while cream cheese contains only 1 g per ounce. The hard cheeses, including Parmesan and sharp Cheddar, often have very little lactose per serving, about 0 to 2 g of lactose per slice. Butter and margarine contain only trace amounts.
Lactose Intolerance
Lactose intolerance is the impaired ability to digest lactose, caused by a deficiency of the enzyme lactase. This intolerance either develops over time as your body produces less lactase, or as a result of injury to the intestinal cells that manufacture the enzyme. Symptoms may include abdominal discomfort, pain, bloating, gas, diarrhea and nausea. People have differing levels of lactase in their bodies and can therefore tolerate different amounts of lactose.
Treatment
Management of symptoms is possible with dietary adjustments. The Dietary Guidelines for Americans 2010 recommend that people choose milk products with lower levels of lactose, consume smaller portions like 4 ounces of milk and select modified versions of lactose-containing foods like lactose-reduced or lactose-free milks, yogurts or cheeses. Products with active cultures that break down lactose may be better tolerated. (reference 5) There are also over-the-counter lactase enzyme tablets or drops that can be taken with foods to help digest the lactose. (reference 4)
References
- Center for Food Allergies: Lactose Intolerance Information
- University of Virginia Health System: Lactose Content of Common Foods
- University of Wisconsin Health; Lactose Intolerance; 2004
- National Digestive Diseases Information Clearinghouse; Lactose Intolerance; June 2009
- USDA: Dietary Guidelines for Americans 2010
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