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Small Intestine

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Small Intestine

By: S. Rennie, LPN

The small intestine is the connection between the stomach and the large intestine. About 20 feet long, it is divided into three sections: the duodenum, the jejunum and ileum. The intestinal glands secrete juices that help with digestion and the primary purpose is to convert partially digested food into energy.1 Most nutrients from digested food get absorbed from the intestines into the blood and then brought to the liver.

Poor nutrition and intestines damaged by alcohol can lead to nutrient absorption difficulties.2 As an example, cells lining the small intestine can be altered from a lack of folate. This then hinders absorption of water, sodium, glucose, some amino acids and fatty acids in the jejunum and ileum.2.3 Carbohydrate, protein and fat absorption are decreased in the duodenum.3

Many enzyme activities needed for proper functioning of the intestines can be disrupted by alcohol consumption. Lactase, for one, is an enzyme that breaks down lactose. A deficiency in lactase can cause lactose intolerance. Those enzymes that help transport nutrients from the intestine to the bloodstream can be compromised by alcohol consumption. It can also inhibit the enzymes that work in the metabolizing of drugs and foreign organic substances. 3

A single episode of heavy alcohol consumption could cause erosions and bleeding in the upper part of the duodenum. This is caused by different reactions: 1. The alcohol itself doing the damage. 2. The release of noxious signaling molecules (i.e., cytokines, histamine, leukotrines) which alcohol signals. Lesions caused by either of these allow large molecules (i.e., endotoxins and other bacterial toxins) to enter the bloodstream and lymph. These molecules can then enter the bloodstream, reach the liver and possibly cause damage to it. One more causal effect is the resulting changes in capillaries that lead to mucosal injuries.3

One last effect is on the muscle movements that help keep food in the small intestine for further digestion. These movements can be slow by alcohol resulting in heightened sensitivity to foods with high sugar contents and faster food movement through the intestines, resulting in diarrhea.4


  1. The Intestine. 03/31/98.

  2. Alcohol and Nutrition. Alcohol Alert. National Institute on Alcohol Abuse and Alcoholism. No. 22 PH 346, October, 1993.

  3. Bode, Christiane, Ph.D. and Bode, J. Christian, M.D., Alcohol's Role in Gastrointestinal Disorders. Alcohol Health & Research World. Vol. 21, No. 1, 1997. 77-78

  4. Alcohol and the Digestive System/Gastrointestinal Tract.

This page was last modified on : 10/28/2013

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