Gluten vs. Irritable Bowel Syndrome (IBS)

Similar symptoms may lead to incorrect diagnoses

Gluten and IBS
Getty Images/Peter Dazeley

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 and the symptoms of non-celiac gluten sensitivity, that list probably looks really familiar... so it's no surprise that it's tough to tell the three conditions apart.

In fact, multiple studies have shown that many cases of diagnosed irritable bowel syndrome are actually a celiac disease in disguise. In addition, some people who have been told they have IBS find relief when they eliminate gluten grains from their diets, even though they've tested negative for celiac disease.

So which is it: celiac disease, gluten sensitivity, or IBS? 

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 or Wheat 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 the gluten-free diet. 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 one study, researchers took 34 IBS patients whose IBS symptoms were controlled on the 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.

Could the Problem Be Something Else in Wheat?

It's possible. Research shows that around three-quarters of people diagnosed with IBS see some relief from their symptoms on what's called the low-FODMAP diet. This diet focuses on eliminating foods with certain complex carbohydrates, because these foods ferment in the large intestine, potentially causing bloating, pain and other IBS-type symptoms.

Now, the gluten grains wheat, barley, and rye contain a type of FODMAP called fructans. Wheat, especially, is generally banned on the low-FODMAP diet, although some experts on the diet say you can eat it in small quantities.

It's likely that some of those who believe they're gluten-sensitive actually are reacting to FODMAPs in their food — one recent study reached this conclusion. However, other studies have indicated that some people who believe they're gluten-sensitive do indeed react to pure gluten. And, there's speculation that other components of wheat and the other gluten grains could play a role in both celiac disease and gluten sensitivity.

There's lots more research to be done before we learn the answers to these questions.

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.

You also can try a low-FODMAP diet to see if that helps your symptoms. Many low-FODMAP recipes also are gluten-free, so it's actually pretty easy to follow both diets at the same time.

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.