|
|
|
 |
|
Sign
up for the NDC Update for the latest dairy nutrition news, fast facts,
free tools for patients, expert nutrition advice and information on updated
dairy nutrition resources.
|
|
 |
|
|
|
Nutrition & Product Information
Calcium Counseling Resource
Lactose Maldigestion/Lactose Intolerance
Research shows that many individuals diagnosed with lactose maldigestion can consume the amount of lactose found in up to two glasses of milk - one consumed with breakfast, one with dinner - without developing gastrointestinal symptoms (i.e., lactose intolerance) (1). Despite this, some people still avoid consuming milk and milk products, the major sources of dietary calcium, because of perceived or real lactose intolerance.
Lactose intolerance is the occurrence of gastrointestinal symptoms resulting from incomplete digestion of lactose, the major carbohydrate in human and cow's milk (2,3,4,5). Lactose-intolerant individuals may experience symptoms - cramps, bloating, gas, diarrhea, and/or nausea - anywhere from 30 minutes to 2 hours after consuming a food or beverage containing lactose (5). The severity of symptoms is influenced by the amount of lactose consumed in relation to an individual's lactase activity, and the diet in which lactose is consumed. Cultural and psychological attitudes, as well as biological factors, influence tolerance to milk, too (2,3).
LACTOSE MALDIGESTION VERSUS LACTOSE INTOLERANCE
A low level of the intestinal enzyme lactase, which breaks down lactose into simpler forms of sugar for absorption into the bloodstream, causes lactose maldigestion (2). Lactose maldigestion is not the same as lactose intolerance (i.e., symptoms). Lactose maldigestion is reduced digestion of lactose due to low levels of the intestinal enzyme lactase. Individuals with lactose maldigestion do not experience symptoms of lactose intolerance, the occurrence of gastrointestinal symptoms, unless the amount of lactose consumed exceeds the amount that can be broken down by available lactase (2). Not all individuals or lactose maldigesters with low lactase levels develop clinical symptoms of intolerance. Also, intolerance (i.e., symptoms) to milk and milk products may or may not result from lactose maldigestion (1,6,7).
About 25% of the U.S. adult population and 75% of adults worldwide are said to be lactose maldigesters or have low lactase levels (2,3,4). The condition is common in African Americans, Hispanics, Native Americans, and Asian Americans. Most infants and young children have high levels of lactase and can readily digest lactose. However, lactase activity declines with age in many ethnic and racial populations (2).
LACTASE DEFICIENCY
There are three basic types of lactase deficiency: primary, secondary, and congenital.
In primary lactase deficiency, lactase activity decreases at variable periods after weaning, depending on an individual's racial/ethnic background. This type is genetically determined.
Secondary lactase deficiency is a temporary condition that results from a disease or medications that damage the lining of the small intestine where lactase is normally active.
Congenital lactase deficiency is an extremely rare condition in which the lactase enzyme is completely absent at birth (2). Unlike other types of lactase deficiency, this type requires complete avoidance of lactose (2).
DIAGNOSIS OF LACTOSE MALDIGESTION AND INTOLERANCE
Many individuals believe they are lactose intolerant (i.e., develop symptoms following lactose intake) when in fact they are not (1,2,3,6,7). In a study involving adults who described themselves as severely lactose intolerant, 30% were able to comfortably digest lactose (6). Some people who do not like or choose not to consume milk or milk products claim to be lactose intolerant (i.e., develop symptoms) (2,8).
Self-diagnosis of lactose intolerance is not advised. It could lead to unnecessary dietary restrictions and possible nutritional shortcomings, or worse, fail to detect a more serious disease (2,3). If gastrointestinal symptoms are chronic, a physician should be consulted. A diagnostic test - such as the lactose tolerance test, the hydrogen breath test, or the stool acidity test - is necessary to confirm lactose maldigestion or reduced lactase levels (4,5). However, these diagnostic tests can exaggerate the prevalence of lactose intolerance (i.e., symptoms). For instance, the breath hydrogen test, the most frequently used test, historically has employed a dose of lactose (50 g) in water or about four times the amount available in a single glass of milk (12 g). Lactose intolerance (i.e., symptoms) can only be confirmed by well-controlled, double blind tests in which neither the client nor the health professional is aware of the lactose-containing test solution or lactose-free placebo. Under these more controlled conditions, lactose intolerance is less common than believed.
A major concern is that children and adults with lactose intolerance may consume little or no milk and milk products, and thereby not get enough calcium and other important nutrients supplied by these foods (2,5). A positive diagnosis of lactose maldigestion (i.e., reduced lactase levels) or even intolerance (i.e., symptoms) does not mean that milk and milk products, and other foods that contain lactose, need to be eliminated from the diet. On the contrary, total elimination of milk and milk products is unnecessary, nutritionally unwise, and may even increase intolerance to lactose. According to the American Academy of Pediatrics (9), children and adolescents should consume calcium-rich foods such as milk, cheese, yogurt and other foods to help build bone mass. Increasing bone mass can help prevent fractures in childhood and reduce the risk for osteoporosis in later years (9). For children with lactose intolerance, the AAP recommends that they consume small amounts of milk. Other alternatives include solid cheeses, yogurt, lactose-free and low-lactose milk, vegetables, and calcium-supplemented foods (9).
Foods from the Milk Group are significant sources of calcium and other essential nutrients like riboflavin, potassium, magnesium, vitamin B12, and high-quality protein. Studies demonstrate that a low calcium intake and/or low milk intake compromises intake of other nutrients (10,11,12,13,14). Studies have also linked low calcium intakes with an increased risk of developing osteoporosis, hypertension, some forms of cancer, and other disorders (15). As mentioned below, gradually increasing intake of lactose-containing foods such as some dairy foods has been demonstrated to improve tolerance to lactose in lactose maldigesters (8,16,17).
The minimum amount of lactose to cause symptoms of intolerance varies among individuals (18). Most people diagnosed with lactose maldigestion can consume the amount of lactose contained in one cup (8 ounces) of milk with a meal, and possibly two cups (16 ounces), one with breakfast and one with dinner, without developing gastrointestinal symptoms (1). Both lactose digesters and lactose maldigesters were able to tolerate the amount of lactose (12 g) in one cup of 2% reduced fat milk served with breakfast, according to a double-blind study (6). In another study, lactose maldigesters consumed a dairy-rich diet (i.e., 2 cups of milk, 1 cup of yogurt, and 2 ounces of cheese) providing about 1,500 mg calcium/day without developing symptoms (7). Lactose maldigestion therefore need not be a major barrier to meeting calcium needs (7). Likewise, African American adolescent girls diagnosed as lactose maldigesters were able to tolerate a dairy-rich diet containing 1,300 mg calcium/day with minimal symptoms (8).
Individuals differ in their ability to tolerate lactose and each individual needs to determine his/her own threshold and adjust lactose intake accordingly (2,5).
TEMPORARY LACTOSE INTOLERANCE
Lactose intolerance can be secondary or temporary due to injury to the small intestine from conditions such as infectious diarrheal disease, inflammatory bowel disease (e.g., Crohn's disease), gastrointestinal surgery, radiation treatment, and certain medications such as antibiotics, cancer drugs, aspirin, and nonsteroidal anti-inflammatory drugs. The ability to digest lactose is restored once the underlying problem is resolved, or when drug treatment is stopped. Diet therapy for temporary lactose intolerance involves limiting lactose-containing foods, depending on the patient's tolerance to lactose. If intolerance to lactose is severe, patients may need to check ingredient labels and avoid products with the following ingredients: milk, lactose, milk solids, whey, curds, nonfat dry milk powder, and skim milk solids. Also, because some prescriptions, over-the-counter medications, and vitamins contain lactose, patients should ask their pharmacist if the medications they take contain lactose.
Treatment of lactose intolerance is based on tolerance levels. For this reason, diet should be individualized and on a "trial-and-error" basis. Milk and milk products should first be introduced in small amounts, especially with foods, and gradually increased in amounts as tolerance improves. Some research indicates that tolerance to lactose can be improved to some extent by gradually increasing intake of lactose-containing foods such as milk and milk products (8,16,17). When African American adolescent girls diagnosed as lactose maldigesters consumed a dairy-rich diet for 21 days, tolerance to lactose improved (8).
MILK AND MILK PRODUCTS AND LACTOSE INTOLERANCE
Milk Products and Low-Lactose Milk
Some milk and milk products are better tolerated than others by lactose maldigesters. Most cheeses, especially those aged for at least six months, such as Cheddar and Swiss, contain little, if any, lactose (2,3,4). During the manufacturing of cheese, most of the lactose is removed with the whey. In addition, during the ripening or aging of cheese, most of the remaining lactose is converted to lactic acid and other by-products. Other foods that contain small amounts of lactose and that generally are well tolerated include: cottage cheese, Farmer's cheese, ricotta cheese, soft cheese (cream cheese), and commercial foods processed with small amounts of milk, milk products, milk solids, or lactose (e.g., bread and baked goods, processed breakfast cereals, lunch meats, salad dressings). Lactose maldigesters appear to tolerate chocolate milk better than unflavored milk (19,20).
Lactose-reduced milk and milk products are also available. Commercial lactase hydrolyzes lactose in milk prior to processing. Lactose-reduced milk contains about 70% less lactose than regular milk. Lactose-free milk has about 99.9% of its lactose hydrolyzed.
Lactase Enzymes
Commercial lactase enzymes, in liquid or tablet form, are sold without prescription, as well. When a few drops of the lactase enzyme are added to a quart of milk, the lactose content is reduced by 70% after 24 hours of refrigeration. Heating milk first and adding twice as much lactase can reduce milk's lactose content by 90% to 100% (2,4,5). In addition, chewable lactase enzyme tablets taken just before a meal or snack can help lactose-intolerant individuals digest lactose-containing foods.
"Live Active Cultures"
Many fermented and culture-containing milk products such as yogurt with "live active cultures" are well tolerated by lactose intolerant children and adults (21,22). The enzyme lactase, produced by starter cultures Streptococcus thermophilus and Lactobacillus bulgaricus used to ferment some milk and milk products, such as yogurt, partially hydrolyzes lactose. But improved lactose digestion is primarily due to autodigestion within the intestine by the microbial enzymes. Lactase in yogurt does not improve the digestion of lactose in other milk and milk products consumed at the same time as yogurt (23).
Yogurt with "live active cultures" is well tolerated by the majority of lactase-deficient individuals, even though yogurt's lactose content can vary widely. Because very high or low temperatures inactivate the bacteria, pasteurized yogurt and frozen yogurt are less likely than fresh yogurt to improve lactose digestion. Lactose digestion and tolerance are similar for frozen yogurt and ice cream but may be tolerated by lactose-intolerant individuals (24). Pasteurized yogurt, cultured buttermilk, and sweet acidophilus milk are tolerated at least as well as regular milk (2,3).
The bottom line is that most lactose maldigesters can include dairy foods as part of their diets, with appropriate modifications in the types and amounts of dairy foods consumed.
|