Is it gluten or is it fructans?

There is a growing popularity in gluten-free diets among the general public for reasons such as perceived health benefits or symptom relief. However, for some patients, could it be something other than gluten that’s causing their symptoms? Here’s what GPs should know.

What is gluten?

Gluten is a protein found in certain grains, including wheat, barley, and rye.

Who should avoid gluten?

Coeliac disease is an autoimmune disease which requires a strict lifelong adherence to a gluten-free diet. For the general population, some gluten containing foods are high in fibre and are an excellent addition to a healthy and balanced diet.

FODMAPs and gluten

While there may be a number of reasons people choose to remove gluten, some people may find that a gluten-free diet improves gastrointestinal symptoms.

Gluten and FODMAPs, particularly fructans, tend to co-exist in many grain foods. For example, wholemeal bread, wheat pasta, muesli, couscous, are some examples of foods that are high in FODMAPs but also contain gluten. On the other hand, many gluten-free alternatives are low in FODMAPs.

Current evidence suggests that it may be the FODMAP content in these foods that is causing symptoms for people, rather than the gluten itself. Studies have found that participants with reported non-coeliac gluten sensitivity experience an improvement in symptoms when following a low FODMAP diet, but no gluten-specific effects when following a gluten-containing diet [1,2].

A more recent 2021 study found similar results. In this study, participants followed a diet low in FODMAPs and gluten, and when given meals high in FODMAPS they experienced gastrointestinal symptoms, whereas there was no difference in symptoms when given meals high in gluten and the placebo [3].

Considerations

There is research to suggest that unnecessary restriction of gluten can lead to reduced gut health and lowered immunity [4-6]. One study found that when following 10 healthy subjects on a low-gluten diet for a month, their stool samples indicated that populations of healthy bacteria decreased and populations of unhealthy bacteria increased, and that the low-gluten diet lowered immune stimulatory effects [4]. One explanation for why this may be the case is that gluten-containing foods are a major source of fibre in the Australian diet and removing them may lead to a diet lower in fibre and prebiotics which are important for gut health.

For patients experiencing gut symptoms and who suspect that gluten-containing foods may be triggering, evidence suggests it may be the fructans causing symptoms rather than gluten itself. An evidence-based elimination diet such as the low FODMAP diet may be an appropriate strategy for some people.

– Sarah Marko, Accredited Practising Dietitian

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References

[1] Biesiekierski JR, Peters SL, Newnham ED, Rosella O, Muir JG, Gibson PR. No effects of gluten in patients with self-reported non-celiac gluten sensitivity after dietary reduction of fermentable, poorly absorbed, short-chain carbohydrates. Gastroenterology. 2013 Aug;145(2):320-8.e1-3. doi: 10.1053/j.gastro.2013.04.051. Epub 2013 May 4. PMID: 23648697.

[2] Skodje GI, Sarna VK, Minelle IH, Rolfsen KL, Muir JG, Gibson PR, Veierød MB, Henriksen C, Lundin KEA. Fructan, Rather Than Gluten, Induces Symptoms in Patients With Self-Reported Non-Celiac Gluten Sensitivity. Gastroenterology. 2018 Feb;154(3):529-539.e2. doi: 10.1053/j.gastro.2017.10.040. Epub 2017 Nov 2. PMID: 29102613. 

[3] Nordin E, Brunius C, Landberg R, Hellström PM. FODMAPs, but not gluten, elicit modest symptoms of irritable bowel syndrome: a double-blind, placebo-controlled, randomized three-way crossover trial. The American Journal of Clinical Nutrition. 2021.

[4] Sanz Y. Effects of a gluten-free diet on gut microbiota and immune function in healthy adult humans. Gut Microbes. 2010 May-Jun;1(3):135-7. doi: 10.4161/gmic.1.3.11868. Epub 2010 Mar 16. PMID: 21327021; PMCID: PMC3023594.

[5] Singh RK, Chang HW, Yan D, Lee KM, Ucmak D, Wong K, et al. Influence of diet on the gut microbiome and implications for human health. J Transl Med 2017. https://doi.org/10.1186/s12967-017-1175-y.

[6] Bonder MJ, Tigchelaar EF, Cai X, Trynka G, Cenit MC, Hrdlickova B, et al. The influence of a short-term gluten-free diet on the human gut microbiome. Genome Med 2016. https://doi.org/10.1186/s13073-016-0295-y.