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When alcohol is consumed, the alcoholic beverages first pass through the various segments of the gastrointestinal (Gl) tract. Accordingly, alcohol may interfere with the structure as well as the function of GI-tract segments. For example, alcohol can impair the function of the muscles separating the esophagus from the stomach, thereby favoring the occurrence of heartburn. Alcohol-induced damage to the mucosal lining of the esophagus also increases the risk of esophageal cancer. In the stomach, alcohol interferes with gastric acid secretion and with the activity of the muscles surrounding the stomach. Similarly, alcohol may impair the muscle movement in the small and large intestines, contributing to the diarrhea frequently observed in alcoholics. Moreover, alcohol inhibits the absorption of nutrients in the small intestine and increases the transport of toxins across the intestinal walls, effects that may contribute to the development of alcohol-related damage to the liver and other organs. KEY WORDS: ethanol metabolism; AODE (alcohol and other drug effects); mouth; esophagus; stomach; intestine; gastric mucosa; intestinal mucosa; gastric lesion; gastric acid; gastrointestinal function; gastrointestinal absorption; muscle; neoplastic disease; toxins; free radicals; etiology; literature review
Among the many organ systems that mediate alcohol's effects on the human body and its health, the gastrointestinal (GI) tract plays a particularly important part. Several processes underlie this role. First, the GI tract is the site of alcohol absorption into the bloodstream and, to a lesser extent, of alcohol breakdown and production. (For more information on alcohol absorption, metabolism, and production in the GI tract, see sidebar, pp. 82-83.) Second, the direct contact of alcoholic beverages with the mucosa1 that lines the upper GI tract can induce numerous metabolic and functional changes. These alterations may lead to marked mucosal damage, which can result in a broad spectrum of acute and chronic diseases, such as acute gastrointestinal bleeding (from lesions in the stomach or small intestine) and diarrhea. Third, functional changes and mucosal damage in the gut disturb the digestion of other nutrients as well as their assimilation into the body, thereby contributing to the malnutrition and weight loss frequently observed in alcoholics. Fourth, alcohol-induced mucosal injuries-especially in the upper small intestine-allow large molecules, such as endotoxin and other bacterial toxins, to pass more easily into the blood or lymph. These...