Diarrhea & Weight Loss

Diarrhea is a symptom that indicates a problem with absorption of nutrients in the intestines. If the cause of diarrhea is not identified, prolonged diarrhea can lead to weight loss. Diarrhea can be caused by infectious microorganisms, inflammatory diseases of the intestines, poorly absorbed carbohydrates and tumors.

Infectious Causes of Diarrhea

Diarrhea is most commonly caused by infectious organisms, some more likely than others depending on a person's past medical history. A history of bloody diarrhea is indicative of infection by invasive microorganisms such as salmonella, E. coli and Shigella; they are invasive because they penetrate the walls of the intestines. A recent history of travel may be useful in identifying an E. coli infection as a likely cause of diarrhea. A person can be infected by these microorganisms by consuming contaminated foods. For example, consuming contaminated poultry and milk may lead to salmonella infection. Consuming ground beef may lead to E. coli infection, and drinking dirty water can lead to Shigella infection. A person with a weak immune system may be susceptible to other diarrhea-causing microorganisms such as cryptosporidium.

Inflammatory Diseases of the Intestines

Crohn's disease and ulcerative colitis are the two most common inflammatory diseases of the intestines. These diseases cause excessive irritation to the walls of the intestines, which leads to the destruction of cells responsible for nutrient absorption. Crohn's disease causes watery diarrhea but in ulcerative colitis, diarrhea is bloody. These infections are controlled by the use of anti-inflammatory medications.

Poorly Absorbed Carbohydrates

Lactose intolerance is a common cause of diarrhea in certain people; according to the book "Harrison's Principles of Internal Medicine," lactose intolerance is common among African Americans and Asians. Lactose intolerance is caused by a deficiency in lactase -- an enzyme needed to absorb lactose in the intestines. Lactose is commonly found in milk; people with lactose intolerance typically complain of diarrhea after drinking milk. Lactose-free milk products are available for people with lactose intolerance.

Tumors of the Intestines

In rare cases, a tumor may cause diarrhea. Hormone-producing tumors, such as carcinoid and gastrinoma, may cause diarrhea by altering the process of digestion. Carcinoid tumors release serotonin, a signaling molecule released by cells of the nervous system; when excess serotonin is released in the intestines, it causes the intestines to move food faster, thereby preventing adequate absorption of water from the stool. Gastrinomas are typically associated with Zollinger-Ellison syndrome, a condition where gastrinomas are present in various regions of the intestines. Gastrinomas release gastrin, a hormone that increases acid secretion in the stomach. The excess gastrin released by gastrinomas results in increased acidity, which can destroy enzymes needed for fat absorption; diarrhea results as a consequence of increased presence of fat in the stool.