These days just about everyone has a friend who has gone on a gluten-free diet and raves about it. Perhaps you’ve tried it yourself. Perhaps digestion improves, and so does well-being. Does that mean that you or your friend is sensitive to gluten?

Maybe not. Surprisingly, you may actually be reacting to a different ingredient in wheat…and in many other foods. Avoiding this particular class of hard-to-digest carbohydrates, called FODMAPs, may improve digestive symptoms in people who believe that they are sensitive to gluten.

That’s not to say that gluten is suddenly fine for everyone. It’s pure poison for the two million Americans with celiac disease, a digestive disease in which the body can’t digest gluten, a protein found in wheat, rye and barley. Nor does it mean that non-celiac gluten sensitivity (NCGS) isn’t real. It’s just that the population with NCGS may be smaller than once believed—and certainly fewer than the 30% of Americans who currently try to avoid gluten in their diets.

The good news is that a careful plan to remove just the FODMAPs that are causing your particular reaction may lead to a less restrictive diet than a gluten-free one—and be more effective in fixing your digestion.


To understand the FODMAP/gluten story, step back to 2011. Australian researchers studied people who didn’t have celiac disease but did have irritable bowel syndrome (IBS), with its symptoms of bloating, stomach pain, and diarrhea and constipation. (As many as 20% of Americans experience these symptoms in this often-undiagnosed and poorly understood condition.) In a randomized placebo-controlled study, the Australians reported that gluten made the 34 study participants’ IBS symptoms worse and that a gluten-free diet reduced symptoms.

That very influential study helped establish the concept of non-celiac gluten sensitivity and boosted the popularity of gluten-free diets.

But then a couple of years later, the same researchers revisited the topic. They examined whether gluten was indeed the cause of symptoms in a group of people who had NCGS. These 37 patients “felt that gluten was the cause of their gut symptoms” says the study’s lead author, Peter Gibson, MD, professor and director of gastroenterology at The Alfred and Monash University in Melbourne, Australia. The study also looked at the effects of FODMAPs, which stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. They’re found in many foods, and some studies were starting to find that they could trigger IBS symptoms.

What the Australians found was surprising…

  • A low-FODMAP diet significantly reduced gastrointestinal symptoms.
  • Participants who had reported improvements in GI symptoms on a gluten-free diet before the study had even fewer symptoms on a low-FODMAP diet.
  • When the researchers “challenged” 37 of the participants by giving them food that contained either no gluten, a small amount of gluten (2 grams), or a large amount of gluten (16 grams, about the amount in 10 slices of wheat bread), there was no difference in symptoms. In other words, gluten had no effect on symptoms.

While the study had a small number of subjects (as did the 2011 one), it was carefully designed to provide reliable clinical results. Not only was it double-blind, so that neither researcher nor subject expectations could affects the results, and placebo controlled, but it was a “cross-over re-challenge” study—each participant got each one of the different diets. “This kind of study is the gold standard way of determining whether a food is causing symptoms,” says Dr. Gibson. “If gluten was the cause of the symptoms, then it would cause greater symptoms than the placebo. It did not. That is why gluten is unlikely to be the culprit in those subjects studied.”


Since that study was published, the benefits of a low-FODMAP diet for people with digestive symptoms has become even clearer. Researchers who’ve been looking for ways to help people with IBS, for example, are almost giddy with excitement—well, as giddy as scientists get in print—with editorials such as “Diet as a Therapy for Irritable Bowel Syndrome: Progress at Last.” One 2014 study of the low-FODMAP diet for IBS concluded: “This high-quality evidence supports its use as a first-line therapy.” A recent study of dieticians found that in their experience, a low-FODMAP diet helps patients with GI symptoms better than the old advice to “eat a healthy diet” while restricting lactose-containing foods and cutting back on caffeine.

To be sure, the debate over whether NCGS is a distinct clinical diagnosis, unrelated to FODMAP sensitivity, at least for some people, continues. One 2015 scientific review concluded that it is not clear whether what is thought to be NCGS is caused by gluten or FODMAPs, for example. However, Alessio Fasano, MD, director of the Center for Celiac Research and Treatment at the MassGeneral Hospital for Children in Boston, pointed out in a 2015 scientific review that people with NCGS often have immunological reactions to wheat and other grains—not just stomach problems. NCGS may contribute to other conditions including chronic fatigue syndrome and autoimmune diseases, he argues. To make matters even more complicated, there are other ingredients in wheat, rye, and barley, such as amylase-trypsin inhibitors (ATIs), that may trigger immune response–related symptoms. He believes a better name for NCGS is non-celiac wheat sensitivity. Going on a low-FODMAP diet wouldn’t address these concerns.

For now, though, if you have unresolved digestive symptoms, it’s clearly time to give a low-FODMAP diet a close look. “Our advice is to try reducing FODMAPs first, since this is an easier diet than a gluten-free diet,” says Dr. Gibson. Based on research, he estimates that about 70% of people with IBS symptoms will benefit.


“The major argument against the low-FODMAP approach is that it is too difficult, but that is the opinion of people who do not know much about how easy the low-FODMAP diet is to implement,” says Dr. Gibson.

It is true that FODMAPs are very common in a typical Western diet. FODMAPs include fructans, found in wheat as well as onions and garlic…fructose, high-fructose corn syrup, and some fruits such as apples and pears…lactose, the sugar in milk and other dairy products…polyols, found in the sweetener sorbitol and in stone fruits such as plums and cherries…and galacto-oligosaccharides, found in beans, lentils and soybeans. However, many individuals are more sensitive to some FODMAPs than others. It’s also the dose of FODMAPs that counts—a little bit is OK but a lot will cause symptoms. So you may need to reduce FODMAPs a small amount to feel better. (That’s why it’s a “low-FODMAP” diet, not a “FODMAP-free diet.”)

That’s good, because many of these foods are very nutritious. It’s best, by far, to get help from a dietician if you want to see whether you would feel better on a low-FODMAP diet—a dietician will guide you through a FODMAP-elimination process in which you will get rid of most or all FODMAPS and then carefully add each type back, in turn, to see which ones cause your symptoms. A dietician can also help make sure you eat a nutritious diet even if you need to eliminate certain classes of foods. To learn more, Monash University has created a low-FODMAP app with information on low- and high-FODMAP foods as well as meal plans.

If you continue to have problems and suspect gluten, on the other hand, do get it checked out. The first action is to find out if you have celiac disease, and there are well-established tests for this. Don’t give up gluten until you know, because having eaten gluten is key to the diagnosis. You may also want to check for a wheat allergy, which is a different beast entirely. If the FODMAP diet doesn’t help and other conditions such as Crohn’s have been ruled out, you may want to consider gluten. Unfortunately, there aren’t lab tests that can establish gluten sensitivity, but you can work with your doctor to go on a gluten-free diet to see if it helps your symptoms. But that should be your last step in this process—not your first!