Symptoms of lactose intolerance in adults include bloating, flatulence, abdominal discomfort, and occasionally diarrhea, after consuming milk or dairy products. The enzyme lactase breaks down lactose into glucose and galactose at the very tips of the villi in the small intestine. Lactose malabsorption is most commonly due to not having enough of the enzyme. This condition is more common in African Americans, Asians, Hispanics, and Native Americans and is less common in Caucasians. If lactose is not digested in the small intestine, it passes into the colon where it is converted to short chain fatty acids and hydrogen gas by bacteria. The colon can absorb some of the byproducts.
Meals with a higher fat load leads to slower gastric emptying and may be less likely to cause symptoms than ingested lactose that quickly passes to the colon. Symptoms from lactose malabsorption typically occur within a few hours of ingestion and resolve after a week of avoiding milk products.
Secondary conditions of lactose intolerance are often due to the disruption of villi in the small intestine. Celiac disease causes shortening of the villi which leads to lactose malabsorption until the villi are restored by adhering to a gluten free diet. Crohn’s disease of the small intestine or infective/radiation induced enteritis also are associated with secondary lactose intolerance, until the disease process is treated. Additionally, small intestinal bacterial overgrowth can be associated with increased fermentation of lactose in the small bowel due to excessive bacteria in the small intestine. #lactoseintolerance, #gas, #bloating
Hammer, H., & Hogenauer, C. (2018). Lactose intolerance: Clinical manifestations, diagnosis, and management. In L.S. Friedman (ed.), UpToDate. Retrieved February 19, 2019, from
https://www.uptodate.com/contents/lactose-intolerance-clinical-manifestations-diagnosis-and-management
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