Q. "Why is gluten ok on a low-FODMAP diet? I thought gluten was bad for people with IBS?"

A: The answer is very simple. Gluten is not a FODMAP. One of the most persistent myths about low-FODMAP diets is that the diet must be gluten-free. Not true. It's an understandable mistake, because wheat, barley and rye are significant dietary sources of both gluten and FODMAPs. Gluten is a protein found in these grains. FODMAPs, on the other hand, are carbohydrates, in this case specific types of fiber called fructans and GOS. Fructans and GOS are oligosaccharides; they put the “O” in FODMAP.

Is gluten a potential cause of GI symptoms? Yes. It's important to remember what a FODMAP Elimination Diet isn't and what it is. It is not "an all-purpose , one-size fits all diet eliminating absolutely everything in the world that might be causing symptoms." It's the very opposite of that, actually. It is a dietary experiment to see whether FODMAPs are a trigger for your gut symptoms. If it helps, great. Work with it. The goal is not the most “clean” diet (no caffeine, no gluten, no red meat, no fat, no FODMAPs, no, no, no...). The goal is discovering the most nutritious, delicious and varied diet you can tolerate.

FODMAPs are one potential trigger for digestive distress. Gluten is another. Some people might learn over time that they need to limit both in their diets, others not.

Already on a gluten-free diet?

If you've been gluten-free for a while before starting a FODMAP elimination diet, its easy enough to continue until the right time comes to "challenge" with gluten to find out whether it truly is a symptom trigger for you.

Of course, if you have a gluten-related disorder such as celiac disease or dermatitis herpetiformus, or if you or your healthcare team has reason to believe you are sensitive to gluten, you can and should continue to choose only gluten-free low-FODMAP foods during the elimination phase. Fortunately, it’s not a difficult modification. since the low-FODMAP diet includes very few products made with wheat, barley or rye due to their FODMAP content.

Everyone else

If you have not been on a gluten-free diet before starting your low FODMAP diet, there is no reason to eat 100% gluten-free now. "Cross contamination" and traces of wheat in your food won't hurt your FODMAP experiment a bit. In fact, if you avoid gluten too carefully during the elimination phase of the low-FODMAP diet, you might interfere with future testing for celiac disease if your doctor decides that is needed. You can even eat a few foods which contain wheat ingredients if they have been lab tested and shown to have low FODMAP serving sizes. For example, authentically made sourdough bread (2 slices) is low-FODMAP, even when made with white or whole wheat flour.

Reference:

Zopf, Y., & Dieterich, W. (2019). Gluten and FODMAPS — Sense of a Restriction / When Is Restriction Necessary. Nutrients, 11, 1–12, 2019.

Originally published March 26, 2015. Reviewed and republished November 14, 2022.

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