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Lactose Intolerance

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Overview


Plain-Language Overview

Lactose Intolerance is a common digestive condition where the body has difficulty digesting lactose, a sugar found in milk and dairy products. This happens because the small intestine does not produce enough of the enzyme lactase, which is needed to break down lactose into simpler sugars. When lactose is not properly digested, it can cause symptoms like bloating, diarrhea, and abdominal pain. These symptoms occur because undigested lactose ferments in the colon, leading to gas and discomfort. The condition primarily affects the gastrointestinal system and can impact dietary choices and nutrition.

Clinical Definition

Lactose Intolerance is defined as the inability to digest lactose due to a deficiency of the brush-border enzyme lactase in the small intestine. This enzyme deficiency leads to malabsorption of lactose, causing osmotic diarrhea and fermentation by colonic bacteria, which produces gas and abdominal symptoms. The most common cause is primary lactase deficiency, a genetically programmed decline in lactase production after weaning. Secondary causes include damage to the intestinal mucosa from infections, celiac disease, or inflammatory bowel disease. The condition is clinically significant because it results in gastrointestinal symptoms that can impair quality of life and nutritional status if dairy intake is not managed. It is distinct from milk allergy, which involves an immune response rather than enzyme deficiency.

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Differential Diagnoses