Irritable bowel syndrome is the most common gastrointestinal diagnosis yet it is not really a disease nor does it have confirmatory diagnostic tests. Rather, it is diagnosed based on a constellation of symptoms and the absence of other diagnoses. Common symptoms attributed to IBS are abdominal pain, cramping, diarrhea, bloating and excess gas. Celiac disease or gluten sensitivity is a common but frequently missed gastrointestinal diagnosis. Ingestion of gluten containing foods in affected individuals commonly causes symptoms attributed to IBS that are relieved with gluten-free diet in at least 10-20% of people misdiagnosed with IBS. Other food intolerances are also a likely a cause of IBS symptoms that may improve with avoidance of certain foods.

IBS is a diagnosis of exclusion. Other causes of symptoms of abdominal pain, diarrhea, constipation, or alternating constipation and diarrhea should be excluded by doctor's review of medical history, a physical exam and some screening laboratory tests and arguably a colonoscopy. The other conditions that traditionally doctors are most concerned about excluding include inflammatory bowel diseases (ulcerative colitis, Crohn's disease) and cancer. Less worrisome but treatable conditions that need to be excluded include lactose intolerance, intestinal infections especially parasites like giardia, and food intolerance. Celiac disease though now known to be very common, affecting approximately one percent of the U.S. population, has been largely ignored as a possible cause of IBS symptoms. Most primary care physicians are aware that diarrhea is a common symptom of Celiac disease but not that it may present in adults and be associated with constipation. Most doctors are unaware that the prevalence of Celiac disease in IBS patients may be as high as 20%.

Typical lab tests ordered by doctors screening for more serious intestinal diseases that may mimick IBS include a complete blood count (CBC) looking for signs of blood loss or anemia (low hemoglobin or hematocrit), signs of inflammation or infection (high white blood cell count and/or platelet count) and stool tests for blood (fecal occult blood test or FOBT) or white blood cells (WBCs or fecal leukocytes). The stool tests are looking for signs of bleeding, infection or inflammation of the intestine. IBS does not cause bleeding or intestinal inflammation whereas inflammatory bowel disease, infection or cancer may. Normal tests are reassurring though do not exclude more serious disease. Most gastroenterologists believe a colonoscopy should be performed.

However, most doctors, even many gastroenterologists, fail to test for Celiac disease though it is common and screening blood tests exist. The reasons for this are many and are more fully explained elsewhere. However, the common incidence, presence of screening tests, and available treatment should make screening for Celiac disease part of the standard evaluation of all patients presenting with symptoms suggestive of IBS before that diagnosis is established.

More recently, food intolerance other than gluten or wheat have been suggested as a treatable cause of IBS. Blood tests for a type of antibody known as IgG have been advocated by several researchers as being helpful for advising people about eliminating or avoiding certain foods as a treatment of IBS. Recent evidence suggests that a significant reduction of IBS symptoms can be achieved in people who avoid foods based on elevated IgG antibodies to foods. Atkinson et. al 2004 reported 10-26% improvement in symptoms in patients compared with controls. Deterioration was noted in those who relaxed their dietary restriction of foods they had avoided because of elevated antibody levels. These findings require further validation and are facing significant resistance to acceptance by many in the medical community, especially in the U.S. However, elimination diets have long been reported effective by many people. The possibility of food intolerance as a reversible cause of symptoms attributed to a syndrome with little other effective treatments (except mostly ineffective treatments in the past and very new medications with limited efficacy and unproven long term safety) should prompt further studies and an openness to dietary trials.

If you have been diagnosed with irritable bowel syndrome I recommend you confirm that Celiac disease has been excluded. Food intolerance should also be considered though testing may not be covered by your insurance and/or accepted by your doctor as valid. Elimination of common foods and their proteins causing intolerance, wheat, barley and rye (gluten); cow's milk protein (casein); soy; and peanuts is worth a try. Be sure to keep a food-symptom diary and re-introduce one food or food protein back into your diet at a time. One diet that effectively eliminates all the major food proteins causing intolerances but may be difficult to follow is the paleo diet (www.thepaleodiet.com).

1. Hoey. "Irritable Bowel Syndrome: Could it be Celiac Disease?" Can Med J. 2002; 166:479-80

2. Sander et al, "Association of Adult Coeliac Disease with Irritable Bowel Syndrome: A Case-Control Study in Patients Fulfilling Rome II Criteria Referred to Secondary Care." Lancet. 2001; 358:1504-8

2. Atkinson W; Sheldon TA; Shaath N; Wharwell PJ. "Food elimination bsed on IgG antibodies in irritable bowel syndrome; a randomised controlled trial." Gut 2004; 53:1459-1464.

3. Isolauri E; Rautava S; Kalliamaki M. "Food allergy in irritable bowel syndrome: new facts and old fallacies." Gut 2004; 53:1391-3.

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