Lactose intolerance: Clinical manifestations, diagnosis, and management
- Heinz F Hammer, MD
Heinz F Hammer, MD
- Associate Professor of Internal Medicine and Gastroenterology
- Division of Gastroenterology and Hepatology
- Medical University Graz, Austria
- Christoph Högenauer, MD
Christoph Högenauer, MD
- Associate Professor of Internal Medicine and Gastroenterology
- Division of Gastroenterology and Hepatology
- Medical University Graz, Austria
Intolerance to lactose-containing foods is common . Clinical symptoms of lactose intolerance include abdominal pain, flatulence, and diarrhea after ingestion of milk or milk-containing products. These symptoms have been attributed to lactose malabsorption, which results from low levels of small intestinal lactase, which may be due to mucosal injury or, much more commonly, reduced genetic expression of the enzyme lactase-phlorizin hydrolase. This topic will review the clinical manifestations, diagnosis, and management of lactose intolerance. Other causes of malabsorption are discussed in detail, separately. (See "Mechanisms of nutrient absorption and malabsorption" and "Clinical features and diagnosis of malabsorption" and "Overview of the treatment of malabsorption".)
●Lactase deficiency — Lactase deficiency is characterized by an intestinal brush border lactase enzyme activity that is lower than that of normal individuals.
●Lactose malabsorption — Lactose malabsorption is characterized by a failure of the small bowel to absorb a sizable fraction of ingested lactose.
●Lactose intolerance — Lactose intolerance is a clinical syndrome in which lactose ingestion causes symptoms (eg, abdominal pain, bloating, flatulence, diarrhea) due to lactose malabsorption.
The prevalence of lactase deficiency has been described in most regions of the world and in people with diverse ethnic backgrounds. However, the prevalence of lactose malabsorption and lactose intolerance is unclear due to methodological limitations of existing studies that have used varying definitions of lactose malabsorption and intolerance. Evaluation of epidemiological trends suggests that the prevalence of lactose intolerance varies across racial and ethnic groups, with the lowest prevalence in Europeans and European Americans and higher prevalence in African Americans, Hispanics, Asians, Asian Americans, and Native Americans. In Africa, some ethnic groups have high rates of lactase intolerance (South Nigerian, Hausa, Bantu), while others have low rates (Hima, Tutsi, nomadic Fulani). The prevalence of lactose malabsorption and intolerance are low in children younger than six years and increases with age [2,3].
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- ETIOLOGY OF LACTOSE MALABSORPTION
- Primary lactose malabsorption
- - Acquired primary lactase deficiency
- - Congenital lactase deficiency
- - Developmental lactase deficiency
- Secondary lactose malabsorption
- CLINICAL FEATURES
- Clinical manifestations
- Laboratory findings
- Diagnostic approach
- Lactose breath hydrogen test
- Lactose tolerance test
- EVALUATION TO RULE OUT A SECONDARY CAUSE
- DIFFERENTIAL DIAGNOSIS
- Dietary lactose restriction
- Enzyme replacement
- Calcium and vitamin D intake
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS