Lactose intolerance is not an allergic reaction to dairy products but rather a compromised ability to digest lactose, which is a sugar found in milk and milk products. A deficiency of the digestive enzyme lactase causes this condition. Cells in the lining of the small intestines produce lactase, This enzyme separates lactose into two simpler forms of sugar called glucose and galactose. The simpler sugars are absorbed into the bloodstream.
Approximately 30 million Americans experience some degree of lactose intolerance by the age of 20. People of Asian, African, Afro-American, Native American, and Mediterranean ethnicity have a higher risk of being lactose intolerant than people from northern and western Europe. Premature infants are more likely to have a lactase deficiency than full-term infants. An infant’s lactase levels do not increase until the third trimester of pregnancy.
Primary lactase deficiency advances over time beginning after the age of two when the body produces less lactase. Intestinal injury associated with severe diarrheal illness such as Crohn’s disease, causes secondary lactase deficiency. Though it can occur at any age, secondary lactase deficiency is more common in infancy.
A person who is lactose intolerant can experience symptoms within 30 minutes to two hours after consuming milk or milk products. Common symptoms include abdominal pain, abdominal bloating, gas, nausea, and diarrhea. The intensity of the symptoms range from mild to severe depending upon the amount of lactase consumed and the person’s degree of tolerance. Since digestive conditions such as irritable bowel syndrome have similar symptoms, the diagnosis of lactose intolerance is not based on symptoms alone. First, a physician will obtain a patient’s medical history and perform a physical examination. Next, the physician recommends eliminating milk and milk products from the patient’s diet for a short time and observing if the symptoms resolve. If further testing is necessary, a hydrogen breath test is administered to adults. Undigested lactose produces high hydrogen levels detectable in the breath.