Dr Jane Muir and Dr Jane Varney

What if avoiding gluten and wheat was helping your symptoms, but not for the reasons you thought?

Wheat and gluten-containing foods are often blamed for triggering gastrointestinal symptoms.

Indeed, a recent CSIRO survey of 1184 adults found that around 11% avoided food containing wheat and gluten.

The most commonly given reasons for going gluten-free were abdominal bloating, abdominal pain and fatigue – common symptoms of irritable bowel syndrome (IBS), a condition that affects one in 7 adults.

Given that coeliac disease is far less prevalent than IBS, affecting only 0.4% (that’s only 4 in a thousand) of Australians, it would appear that too many healthy people are unnecessarily avoiding gluten and wheat.

It’s a worldwide phenomenon and, while the scientific evidence supporting the benefit of these dietary restrictions is lacking (in the absence of coeliac disease, wheat allergy or IBS), the demand for wheat and gluten-free products is growing at 34% per annum.

However, our team at Monash University has found that there are a number of components in gluten-containing grains (such as wheat, rye and barley) that may trigger gut symptoms in people with IBS. And we have named these carbohydrate components FODMAPs*.

FODMAPs are poorly absorbed in the small intestine and rapidly fermented by bacteria in the large bowel, producing gas and triggering gut symptoms in IBS sufferers.

Gluten-containing grains such as wheat are particularly high in the FODMAP fructan, so by choosing gluten-free food people tend to eat fewer fructans, leading to better symptom control3.

We have also investigated the role of gluten in triggering gut symptoms in people without coeliac disease.

One study conducted among 37 people with IBS who claim to have symptom relief when following a strict, gluten-free diet [so called non-coeliac gluten sensitivity (NCGS)], required participants to consume a gluten-free, low FODMAP diet for two weeks. They were then randomly assigned to one of three diets – all low FODMAPs – (but contained either high gluten, low gluten or zero gluten).

While all participants experienced gastrointestinal symptom improvements on the initial low FODMAP diet, no independent, gluten-specific effects were observed.

In other words, whether they ate gluten or not made no difference to symptoms.

The study calls the clinical diagnosis of NCGS into question and suggests that FODMAPs, not gluten, are the trigger of gastrointestinal symptoms in people with so-called, NCGS.

However, our team has also discovered that gluten and FODMAPs tend to co-exist in foods. As outlined in this graph (below), gluten-free grain and cereal products were lower in FODMAPs (mostly fructans and GOS) compared to gluten-containing products.

fodmap content

So, by choosing gluten-free grain and cereal products, people are often choosing low FODMAP and this relationship might explain why individuals without coeliac disease report symptom relief on a gluten-free diet.

*FODMAPs stands for Fermentable Oligo- Di- and Mono-saccharides And Polyols. FODMAPs are found in a wide variety of food, for instance lactose (found in milk), free fructose (in pears, apples), fructans and fructo-oligosaccharides (in wheat, rye, onions, garlic) and galacto-oligosaccharides (in legumes).

Dr Jane Muir (PhD) is Head of Translational Nutrition Science at the Department of Gastroenterology – Monash University.

Dr Jane Varney (PhD) is a research dietitian at Department of Gastroenterology – Monash University.

Last Reviewed: 21/08/2015