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By Alice Klein 10 November 2017
Gluten might not be the bad guy after all. Evidence suggests it may be the fructan molecules in wheat that cause stomach problems in people with an intolerance.
About 1 per cent of people have coeliac disease, an autoimmune disorder that makes them react badly to gluten proteins in wheat. But a further 12 per cent feel ill after eating wheat-based foods like bread and pasta, despite not having coeliac disorder.
Now it looks like it may not actually be gluten that causes problems for these people with “gluten sensitivity”.
In 2013, a study of non-coeliacs who ate gluten-free to relieve gut issues found no difference in symptoms when these people ate identical meals that either lacked gluten, or were full of it. This suggested gluten has no effect, prompting Jane Muir and Peter Gibson at Monash University in Australia and their team to wonder if there might be an alternative culprit.
Separating the wheat from the chaff
They suspected fructans, which are a type of sugar chain found in wheat, barley and rye, as well as onions, garlic, chickpeas, cabbage, and artichokes.
To test this, they recruited 59 non-coeliac adults currently following gluten-free diets for gut sensitivities. They gave these volunteers three types of cereal bars containing gluten, fructans, or neither, and the participants ate one of these every day for seven days, with week-long spaces in-between each type of bar. The bars all looked and tasted the same, and the participants did not know which ones they were eating.
The fructan bar triggered 15 per cent more bloating and a 13 per cent increase in overall gastrointestinal symptoms, compared to the control bar. The gluten bar, however, had no effect.
This may explain why people with irritable bowels often improve on gluten-free diets but don’t make a full recovery, says Muir. By cutting out wheat, they eliminate a large portion of fructans from their diets, but they can still run into trouble eating other high-fructan foods like onions and garlic. Some gluten-free products like chickpea crisps also contain fructans.
It may also explain why few placebo-controlled studies have managed to find that gluten has any effect, and why it has been so difficult to find out how gluten may cause problems for non-coeliacs, says Gibson.“Gluten was originally assumed to be the culprit because of coeliac disease, and the fact that people felt better when they stopped eating wheat,” he says. “Now it seems like that initial assumption was wrong.”
It’s possible that a small minority of non-coeliacs do react to gluten and studies so far haven’t been big enough to readily detect them, Gibson says. “But certainly the evidence points to fructans being more of a problem.”
Difficult to digest
The team’s findings fit with six recent trials that suggest about 70 per cent of people with irritable bowel syndrome feel better when they cut out fructans and other nutrients from a food group known as FODMAPs.
This stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. These are a collection of short sugar chains that are difficult to digest. They draw in water and are fermented in the large intestine by gas-producing bacteria, causing the gut to stretch slightly. People with irritable bowel syndrome are more aware of this because they have hypersensitive nerve endings in their guts.
Katie Ellard, a gastroenterologist at Mater Hospital in Sydney, Australia, says many clinicians are now prescribing low-FODMAP diets to people with stomach troubles. “Once coeliac disease has been ruled out, I still recommend knocking off wheat to see if that helps, but I explain that it’s to eliminate fructans not gluten from their diet,” she says.
If fructans do turn out to be the real problem, it will open up a range of foods that were previously off-limits, says Ellard. Soy sauce, for example, contains gluten but is low in fructans, while the fermentation process used to make sourdough bread strips away wheat’s fructans.
Journal reference: Gastroenterology, DOI: 10.1053/j.gastro.2017.10.040
