A low FODMAP diet is not the same as a gluten-free diet, though the two overlap significantly. FODMAPs are short-chain carbohydrates that ferment in the gut, while gluten is a protein. They happen to coexist in many of the same grains, which is why cutting out wheat often improves symptoms regardless of which approach you follow. But the distinction matters: you can eat gluten on a low FODMAP diet, and plenty of gluten-free products are high in FODMAPs.
Why FODMAP and Gluten-Free Get Confused
Wheat, rye, and barley contain both gluten (a protein) and fructans (a type of FODMAP carbohydrate). When someone cuts out wheat and feels better, it’s natural to credit gluten as the problem. But research from Monash University found that these grains contain high levels of fructans alongside gluten, and the two tend to coexist in foods. Going gluten-free automatically reduces your fructan intake, so the symptom relief people experience is often from lower FODMAPs, not from removing gluten itself.
A 2018 double-blind crossover study published in Gastroenterology tested this directly. Researchers challenged 59 people who had put themselves on gluten-free diets (after celiac disease was ruled out) with isolated gluten, isolated fructans, or a placebo. Of those 59 participants, 24 reacted most to fructans, 22 reacted most to placebo, and only 13 had their strongest symptoms after consuming gluten. The fructan group had significantly higher bloating scores than the gluten group. In other words, most people who believed they were gluten-sensitive were actually reacting to a carbohydrate, not a protein.
When You Need Gluten-Free vs. Low FODMAP
Celiac disease is an autoimmune condition where gluten directly damages the lining of the small intestine. If you have celiac disease, you need a strict, lifelong gluten-free diet. IBS, by contrast, is a functional disorder where the gut works abnormally but no tissue damage occurs. The trigger for IBS symptoms is typically FODMAPs: poorly absorbed carbohydrates that travel to the large intestine, where gut bacteria ferment them and release gas. That fermentation causes bloating, abdominal pain, diarrhea, or constipation.
These conditions produce very similar symptoms, which is why they’re frequently confused and often require specialist evaluation to distinguish. But the dietary solutions are different. A person with celiac disease needs to avoid gluten protein completely. A person with IBS needs to reduce specific fermentable carbohydrates, and gluten itself is not the concern.
Gluten-Containing Foods That Are Low FODMAP
Because the low FODMAP diet targets carbohydrates rather than proteins, some foods containing gluten are perfectly fine on the diet. Spelt sourdough bread is a key example. Traditional sourdough fermentation lasting around 12 hours can reduce fructan levels by up to 69%. The long fermentation gives bacteria time to break down the FODMAPs before you eat the bread, while the gluten protein remains intact. Monash University specifically suggests trying spelt sourdough if you have IBS and suspect gluten is the culprit. It’s a practical way to test whether your symptoms come from fructans or gluten.
One caveat with sourdough: the same fermentation process that reduces fructans can increase mannitol, another FODMAP, by as much as 550%. Not all sourdough is created equal, and the final FODMAP content depends on fermentation time, starter culture, and the grain used. Look for traditionally fermented sourdough rather than commercial bread that uses sourdough flavoring with added yeast for speed.
Gluten-Free Foods That Are High FODMAP
This is where people run into trouble. Assuming “gluten-free” means “low FODMAP” can backfire. Fructans exist in far more than just grains. Onions, garlic, honey, watermelon, legumes, and certain dairy products are all naturally gluten-free yet high in FODMAPs. A gluten-free pizza topped with onions and garlic, or a gluten-free cookie sweetened with honey or agave, could easily trigger IBS symptoms.
Processed gluten-free products sometimes include high FODMAP ingredients as flavor enhancers or binders. Inulin (a concentrated form of fructan often listed as “chicory root fiber”) is commonly added to boost the fiber content of gluten-free breads and snack bars. If you’re following a low FODMAP diet, reading ingredient labels matters more than checking for a gluten-free certification.
Grains That Are Both Gluten-Free and Low FODMAP
If you want to play it safe on both fronts, several whole grains are naturally free of both gluten and high FODMAP carbohydrates. Monash University has lab-tested the following and confirmed them as low FODMAP at standard serving sizes:
- Rice (brown)
- Quinoa (grain, flakes, flour, and quinoa pasta)
- Oats (whole, quick, and oatmeal)
- Corn (on the cob, polenta, tortillas, and popcorn)
- Buckwheat (kernels and flour)
- Millet (grain and flour)
- Amaranth (puffed)
- Sorghum (flour)
These are safe staples for anyone navigating both dietary restrictions, whether you have celiac disease alongside IBS or you’re in the elimination phase of a low FODMAP diet and want to minimize variables. Oats are technically gluten-free but can be cross-contaminated during processing, so look for certified gluten-free oats if celiac disease is a concern.
How to Figure Out Your Actual Trigger
If you’ve been eating gluten-free and feeling better, it’s worth determining whether gluten or fructans are the real issue. The low FODMAP diet has a built-in method for this: after two to six weeks of eliminating high FODMAP foods, you systematically reintroduce them one category at a time to identify your personal triggers. During this process, you can test fructan-containing foods and gluten-containing foods separately.
Trying a slice of spelt sourdough bread (which contains gluten but is low in fructans) is one practical test. If you tolerate it fine, gluten likely isn’t your problem, and you can focus on managing fructan intake instead. This distinction opens up your diet considerably, since you’d only need to limit specific high fructan foods rather than every product containing wheat, rye, or barley.