DIETARY MANAGEMENT

A positive diagnosis of lactose maldigestion or even lactose intolerance (symptoms) does not mean that milk and other dairy foods that contain lactose must be eliminated from the diet (1,16,19,20,24-29,33). Doing so is unnecessary for the majority of patients, nutritionally unwise, and not recommended (4,6,10,13,18,21). Reducing consumption of dairy products due to concerns about lactose intolerance can result in a lower intake of milk’s nutrients, especially calcium, a nutrient often limited in the diets of many Americans (10,34,35). A calcium-poor diet is associated with increased risk of osteoporosis and other diet-related chronic diseases (1,3,19,33).

The goal for managing lactose intolerance is to remain symptom-free while meeting nutrient needs, especially for calcium (13,19,33). Management should be individualized and periodically reevaluated as symptoms are related to the amount of lactose consumed at a given time. As indicated below, several strategies are available to enable lactose maldigesters to comfortably include dairy foods as part of a nutritious diet (1,3,11,13,18,29,33,36).

The Amount of Lactose Consumed. Each individual needs to determine how much lactose can be tolerated at a given time and adjust intake accordingly (1,11,24,26). For example, one can try consuming less than 1/2 cup milk with food and gradually increase the serving size until symptoms just begin to develop (1). Well-controlled, clinical studies have demonstrated that people diagnosed with lactose maldigestion can comfortably consume the amount of lactose in one cup (8 ounces) of milk with a meal or two cups in divided doses over the day with food (16,24,26). Moreover, lactose maldigesters have been shown to tolerate a dairy-rich diet containing 1,300 to 1,500 mg calcium/day (equivalent to at least four servings of dairy foods) (27,28). Consuming milk with meals or solid foods improves tolerance to lactose by delaying gastric emptying, which allows the body more time to digest lactose and reduces the amount of undigested lactose that reaches the colon at any given time (13,37,38).

Types of Dairy Foods. Lactose maldigesters tolerate some types of dairy foods better than others. Chocolate milk may be better tolerated than white milk (38-40). Whether or not whole milk is better tolerated than fat-free milk and aqueous solutions of lactose is controversial (1,13). Hard, aged cheeses (e.g., Cheddar, Swiss, Parmesan, Colby), due to their negligible amount of lactose and high content of solids, are generally well tolerated by lactose maldigesters (1,13,19,29). Aged cheeses contain minimal lactose because of its removal in the whey during cheese-making and the conversion of any remaining lactose entrapped in the curd to lactic acid and other acids during aging (17).

Yogurts with live, active cultures can be comfortably consumed by some lactose maldigesters (1,13,41-46). The ability to digest the lactose in yogurt is explained by the release of bacterial b-galactosidase or lactase from the yogurt starter cultures (e.g., Lactobacillus bulgaricus and Streptococcus thermophilus) after consumption. Also, yogurt’s semi-solid state delays gastric emptying and intestinal transit time which slows delivery of lactose to the intestine (13,44-46). Tolerance to frozen yogurt and ice cream is similar, although lactose maldigesters generally tolerate these foods less well than nonfrozen yogurts (47). Kefir, a fermented milk, has been demonstrated to be as well tolerated as yogurt by lactose maldigesters (48). Whether unfermented milk with bacterial starter cultures such as sweet acidophilus milk or yogurt milk improves lactose tolerance is controversial (1,49). The addition of probiotic bacteria (i.e., live microorganisms which when consumed in adequate amounts confer a health benefit to the host) such as L. acidophilus to dairy products may alleviate symptoms of lactose intolerance, although the effects vary according to the specific probiotic, its strain, and concentration (1,13,50).

Adaptation. Some studies demonstrate that tolerance to lactose can be improved with continuous exposure to lactose-containing foods, especially milk (1,13,28,51,52). Adaptive changes in colonic functions (motility, transit, pH) and gut microflora (e.g., increased microbial b-galactosidase activity) are suggested as possible mechanisms for this response (13).

Lactose-free Dairy Products and Lactose Digestive Aids. Lactose-free (lactose-hydrolyzed) milk and other milk products are readily available for individuals who have difficulty tolerating lactose (1,11,13,19,53). Intake of exogenous lactase in tablet or liquid form is a practical strategy allowing lactose maldigesters to readily consume lactose-containing dairy foods (1).