[Frequent causes of diarrhea: celiac disease and lactose intolerance]

Celiac disease and lactose intolerance are both relatively frequent diseases with symptoms occurring after ingestion of certain food components. In celiac disease wheat gluten and related proteins of other cereals induce an inflammatory disease of the small intestine in predisposed individuals, leading to gastrointestinal and extraintestinal symptoms. Moreover, there is an association with many other diseases and besides classic symptoms (diarrhea, weight loss, malabsorption) atypical courses with less or lacking gastrointestinal symptoms exist. The prevalence is about 1 : 100 (Europe, USA) and higher than supposed earlier. Diagnostic criteria include serologic tests (tissue transglutaminase antibody, endomysial antibody) and characteristic small bowel histology (lymphocytic infiltration, villous atrophy). Therapy is a strict and lifelong gluten-free diet. Rarely, refractory disease or lack of compliance are associated with increased risk of malignancy and worse prognosis. Lactose intolerance is attributed to low intestinal lactase levels, due to reduced genetic expression or mucosal injury and consequent intolerance to dairy products. The frequency is varying in different ethnic groups, occurring in 10-15% of Northern European people. Intensity of clinical symptoms (diarrhea, abdominal pain, bloating) depends on the amount of ingested lactose and individual activity of intestinal lactase. The capacity of lactose malabsorption can be measured using the noninvasive lactose breath hydrogen test. The treatment is based on a reduced dietary lactose intake or in case of secondary form treatment of the underlying disease.