Patients who suffer from irritable bowels experience recurrent bouts of abdominal pain accompanied by diarrhea or constipation. Although these are the main symptoms, other common complaints include whitish mucous in stools, cramping, bloating and flatulence. In the 2008 edition of "Harrison's Principles of Internal Medicine," Dr. Chung Owyang, chief of gastroenterology for the University of Michigan Health System, explains that, while the primary cause of irritable bowels is believed to be overactive nerves in the gastrointestinal tract--a condition known as "visceral hypersensitivity" or "hyperalgesia," other problems such as bacterial overgrowth and diet also contribute.
Visceral Hypersensitivity
In all people, sensory nerve endings in the intestine communicate with the spinal cord, which forwards signals on the brain or sends them back to other nerve endings in the intestine in the form of a reflex arc. People experience signals sent to the brain as pain. Reflex arcs produce non-sensory responses, such as secretion of fluids or contraction of the muscles in the intestinal walls. For reasons that aren't well understood, in people with irritable bowels, these nerve endings react to stimuli that normally wouldn't provoke a response. According to a 2010 report in the journal Gut Pathogens, doctors call this phenomenon visceral hypersensitivity. The result of visceral hypersensitivity in people with irritable bowels is abdominal pain and either constipation or diarrhea, depending on whether the reflex arc causes the bowels to secrete too much fluid or too little and the muscles to contract too often or not often enough.
Bacterial Overgrowth
The human intestine represents the most densely populated ecosystem on earth, with more than one trillion organisms---mostly bacteria---per gram of fecal material. In some cases, patients develop irritable bowel syndrome after a gastrointestinal infection, surgery or some other event that disrupts this ecosystem. Some patients may have too many bacteria in their intestines. Others have the wrong kinds. Regardless, patients with suspected bacterial overgrowth frequently find that irritable bowel symptoms improve after treatment with intestine-specific antibiotics or the addition of probiotics, which are "good" bacteria that inhibit and sometimes kill "bad" bacteria that cause disease.
Diet
Some people experience irritable bowel symptoms because of the foods that they eat. Common food triggers include dairy products, fatty foods, chocolate, alcohol, caffeine and carbonated beverages. Food triggers may relate to mild deficiencies in the digestive enzymes that break down fats and sugars such as lactose, raffinose and fructose. Eating small meals, avoiding these foods or taking supplemental digestive enzymes such as lactase, beta-glycosidase and pancrelipase can help. The first two are available without a prescription, marketed under brand names such as Lactaid, Lactrase and Beano. Pancrelipase is available by prescription only, either as generic pancrelipase or brand names such as Creon and Pancrease.
References
- Irritable Bowel Syndrome (Chapter); C. Owyang; In: "Harrison's Principles of Internal Medicine, 17th edition;" A.S. Fauci et al. (eds.); 2008
- "Gut Pathogens;" Current Insights into the Pathophysiology of Irritable Bowel Syndrome; T. Karantanos et al.; May 2010
- "Clinical Nutrition;" Therapeutic Use of Probiotic Formulations in Clinical Practice; T. Iannitti and B. Palmieri; 2010
- National Institutes of Health: What I Need to Know about Irritable Bowel Syndrome
