Consumption of cow’s milk and milk products is associated with overall diet quality and adequacy of intake of many essential nutrients including calcium, potassium, phosphorus, protein, vitamins A, D (if fortified), and B12, riboflavin, and niacin. Unfortunately, some individuals may avoid milk and milk products unnecessarily because of adverse reactions to these foods.

Milk protein allergy and lactose intolerance underlie most adverse reactions to cow’s milk and milk products. Many differences exist between these conditions, including their cause, prevalence, prognosis, clinical symptoms, diagnosis, and management.

Cow’s milk allergy is an immunologically mediated response to one or more of cow’s milk proteins. Lactose intolerance, a non-immunological reaction, is the occurrence of symptoms after persons with low levels of the enzyme lactase (lactose maldigesters) consume lactose (milk sugar) in amounts exceeding lactase’s ability to digest it. Cow’s milk protein allergy occurs primarily in infancy and early childhood. Approximately 2% of the pediatric population is affected by cow’s milk allergy. Moreover, the condition tends to be outgrown by 5 years of age. In contrast to cow’s milk allergy, which occurs primarily in infancy and young childhood, lactose intolerance (symptoms) seldom occurs prior to preadolescence. Although lactase activity begins to decline after weaning in genetically predisposed individuals, whether or not the condition becomes symptomatic depends on a variety of biological, psychological, and dietary factors.

An accurate diagnosis of adverse reactions to cow’s milk is critical to ensure an effective dietary management strategy and/or to avoid the unnecessary elimination of cow’s milk from the diet. Strict avoidance of cow’s milk, milk products, and some food ingredients derived from cow’s milk (e.g., casein, whey protein concentrate), with careful attention to the nutritional adequacy of the diet, may be indicated if a diagnosis of cow’s milk protein allergy is made. Fortunately, milk protein allergy in infants and young children tends to be a transient condition. As a result of the new U.S. Food Allergy Labeling and Consumer Protection Act, the presence of cow’s milk proteins (e.g., casein) can now be readily identified in food products.

Although many people attribute gastrointestinal symptoms to lactose intolerance, controlled clinical trials indicate that lactose is not a major cause of symptoms for lactose maldigesters who consume a typical serving of dairy products (e.g., a cup of milk). Several strategies are available to improve tolerance to lactose. These include consuming milk in smaller amounts more often throughout the day, especially with meals; eating yogurt with live, active cultures; and consuming aged cheeses such as Cheddar. Also, lactose-reduced dairy foods and lactase enzymes are available. Some research demonstrates that tolerance to lactose is improved with repeated exposure to lactose-containing foods such as milk. With careful management, most lactose maldigesters can comfortably consume 3 servings of calcium-rich dairy foods (milk, cheese, yogurt) a day, as recommended by the Dietary Guidelines for Americans.

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