When you have irritable bowel syndrome, or IBS, your digestive symptoms can run the gamut from diarrhea to constipation, and probably include bloating, gas and abdominal pain as well.
If you're familiar with the symptoms of celiac disease, that list probably looks really familiar... so it's no surprise that it's tough to tell the two conditions apart. In fact, multiple studies have shown that many cases of diagnosed irritable bowel syndrome may actually be celiac disease in disguise.
And to add to the confusion, there's also growing evidence that a subset of people with IBS who definitely don't have celiac disease may in fact have non-celiac gluten sensitivity, and therefore will still benefit from a gluten-free diet.
Celiac Disease Affects the Small Intestine, IBS Affects the Colon
Irritable bowel syndrome is thought to affect up to 15% of the population. People with IBS may have urgent diarrhea, constipation, or a combination of both, in addition to other gastrointestinal symptoms, such as gas and bloating.
IBS mainly involves your large intestine, also known as your colon. As food passes through, your colon becomes "irritable" (hence the condition's name) and acts up. There's no known cause for IBS and no cure, although you can treat it with prescription or over-the-counter medications, along with lifestyle changes.
Although it can cause unpleasant and sometimes downright nasty symptoms, irritable bowel syndrome doesn't cause any damage to your intestinal tract. It's known as a "functional disorder," in which your digestive system functions poorly but isn't actually damaged.
Unlike Celiac Disease, There's No Test for IBS
Doctors don't test for IBS; instead, they rule out other disorders first and then consider whether your IBS symptoms meet the criteria for the condition.
And that's where mistaken diagnoses can come in. If your physician isn't up-to-date on the latest celiac disease research for example, if she mistakenly believes that people with celiac disease cannot be overweight or have constipation as their primary digestive symptom then it's possible that she won't consider ordering celiac disease tests before diagnosing you with IBS.
Sadly, this is a very common problem. Researchers who have tested IBS patients for celiac disease have found between 4% and 10% of those IBS patients actually have celiac, meaning a gluten-free diet should help to improve or eliminate their IBS symptoms.
Gluten Sensitivity May Play Role in IBS
It's also possible that some IBS patients who have been tested for celiac disease and came up negative may benefit from a gluten-free diet. Two recent studies have found that a subset of people with IBS, but without celiac disease, suffer from non-celiac gluten sensitivity and see their IBS symptoms improve or clear up when they eat gluten-free.
In the first study, researchers took 34 IBS patients whose IBS symptoms were controlled on a gluten-free diet and assigned 19 of them to eat gluten (two slices of bread and a muffin) every day for six weeks. The other 15 ate non-gluten-containing bread and muffins. After one week, those IBS patients eating the gluten foods reported significantly more pain, bloating, tiredness, constipation and diarrhea than the control group, indicating that the symptoms in this group of IBS sufferers were triggered at least in part by gluten.
Another study conducted celiac disease genetic tests and a particular celiac blood test on people with IBS whose primary symptom was diarrhea, and then had them follow the gluten-free diet for six months. A total of 60% of those IBS patients who were positive for a celiac disease gene and in the blood test, plus 12% of those who didn't carry the gene and who received negative results on the blood test, found their IBS symptoms improved or resolved entirely on the gluten-free diet.
Bottom Line: Get Tested for Celiac, or Try Gluten-Free Diet
If you've been diagnosed with irritable bowel syndrome but haven't been tested for celiac disease, you should talk to your physician about ordering the celiac disease blood tests.
If you have been tested but came up negative for celiac, you might want to consider a trial of the gluten-free diet anyway. Currently, there are no accepted medical tests to diagnose gluten sensitivity, so the only way to determine if you have it is to remove gluten from your diet and see if your symptoms clear up.
Of course, it's possible to have both IBS and celiac disease, and many people with celiac disease find they still have intermittent digestive problems. In many cases (but not all), you can trace those digestive problems to gluten cross-contamination. But if you continue to have problems even after eliminating all possible hidden gluten from your diet, you may want to talk with your physician about the best ways to manage your IBS.
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Ford A. et al. Yield of Diagnostic Tests for Celiac Disease in Individuals With Symptoms Suggestive of Irritable Bowel Syndrome: Systematic Review and Meta-analysis. Archives of Internal Medicine. April 13, 2009, Vol. 169 No. 7.
Wahnschaffe U. et al. Celiac disease-like abnormalities in a subgroup of patients with irritable bowel syndrome. Gastroenterology. 2001 Dec;121(6):1329-38.
Wahnschaffe U. et al. Predictors of clinical response to gluten-free diet in patients diagnosed with diarrhea-predominant irritable bowel syndrome. Clinical Gastroenterology and Hepatology. 2007 Jul;5(7):844-50.