Gluten-free foods. Photo: Eddie Jim
On current assumptions, about 1 million Australians today will go to significant effort and expense to consume foods that are free of gluten.
A significant number – about 1 per cent of the population – will do so because they have a serious condition called coeliac disease, the only remedy for which is lifelong avoidance of gluten.
For the rest, however – the vast majority – the decision to adopt a diet devoid of this particular protein is based on the assumption that it is a healthy thing to do. And to some, perhaps mos, of this cohort, the evidence appears clear. They eat food containing gluten, such as bread or pasta, and their bellies distend, discomfort occurs, and rear-end misbehaviour ensues.
Professor Peter Gibson conducted a study in which gluten-free foods produced the symptoms of gluten intolerance in some participants. Photo: Eddie Jim
There's no doubt that this condition, dubbed Non-coeliac Gluten Sensitivity (NCGS), is widespread. One estimate puts the number of NCGS cases at the same level as type-2 diabetes. Its existence in part fuels a large and growing market for a wide range of gluten-free products, which, in the US alone, is tipped to exceed $15 billion this year.
One Australian report calls NCGS a "significant public health matter". There is, however, just one problem. Scientists in Adelaide, Melbourne and Belgium have recently published several studies, all of which suggest the same thing: NCGS probably has nothing to do with gluten.
Indeed, one study found people identifying as gluten-sensitive reported symptoms even when on an unrevealed gluten-free diet. Another found some unlikely correlations between claimed gluten-sensitivity and other factors including gender and beliefs. These factors have led to speculation that gluten-sensitivity might be primarily psychological in essence, a mindset determined by diet fads and fashionable ideas about "good" and "bad" foods.
It is an idea firmly rejected by one of the leading lights in the field Peter Gibson, professor of gastroenterology at the Alfred Hospital and Monash University.
"That NCGS is 'in the head' or is psychological has never been a contention we have supported," he told Fairfax Media. "If people have gut symptoms, then they have gut symptoms."
Professor Gibson is a fearless researcher in his field – so much so that prominent US science writer Maggie Koerth-Baker recently dubbed him her "new science hero". The accolade stemmed from a 2013 report he co-authored wherein he challenged his own previously published findings – and reversed his original conclusion that NCGS was a real thing.
In 2011, Professor Gibson led a research team that concluded, after many dietary tests, that some non-coeliacs experienced pain and bloating after eating foods containing gluten. The team's report caused a sensation. It provided the first clinically validated evidence of the condition – and fuelled strong growth in the gluten-free sector of the manufactured food market.
Professor Gibson's heroism, as Koerth-Baker saw it, stemmed from his subsequent decision to challenge his own results. He and his team decided to redesign and repeat the tests – this time with tighter controls on other elements found in gluten-rich foods.
People with reported NCGS were put on rigorously maintained diets, containing no low or high amounts of gluten. The volunteers had no idea which diet they were on at any given stage. The researchers found, remarkably, that reports of gut symptoms were generally not affected at all by levels gluten intake.
In an article published last year in the academic journal Current Allergy and Asthma Reports, Professor Gibson and his team concluded: "On current evidence the existence of the entity of NCGS remains unsubstantiated."
One of the team members, Dr Jessica Biesiekierski, now at the University of Leuven in Belgium, offered a clarification to Fairfax Media. "There is some evidence that NCGS may exist," she said, "but probably only in a very small number of people."
Professor Gibson and Dr Biesiekierski noted a strong influence in their results that they termed "nocebo". The opposite of placebo, the nocebo effect is when a harmless substance induces harmful effects – in this case, gluten-free foods producing the symptoms of gluten intolerance.
This may imply a psychological basis to at least some cases of reported gluten sensitivity. A report by the CSIRO published in March potentially supports this idea. Professor Gibson, however, rejects the idea outright. Instead, his team suspects another food component is the real culprit.
Gluten is a type of protein found primarily in wheat, rye, barley and oats. A gluten-free diet involves steering clear of food made from these grains, including bread, pasta, most breakfast cereals, and many cakes and biscuits.
Professor Gibson's nocebo results, however, if not psychological, suggest that something else present in these foods is causing the reported discomfort. The Monash-Leuven research points not to a protein, but to a group of carbohydrates collectively known by the awkward acronym FODMAPs.
"The real issue is what is it in wheat that causes the bloating and other gut symptoms, not whether it is all imaginary – this is most definitely not the case," Professor Gibson said.
"The evidence is much stronger that FODMAPs are a major culprit in causing gut symptoms."
The acronym stands for "fermentable oligo-saccharides, disaccharides, mono-saccharides and polyols". Collectively, they are carbs that the gut can struggle to digest. The "fermentable" tag implies they produce gas, which results in swelling and discomfort – symptoms typical of NCGS and a similar condition known as irritable bowel syndrome.
There is an interesting coincidence in all this. Among the richest sources of FODMAPs are wheat and other grains. A gluten-free diet, therefore, is also a FODMAP-free diet, which might explain why giving up bread and pasta often reduces symptoms, even though, it appears, gluten didn’t cause them in the first place.
Dr David Topping, chief research scientist at CSIRO Animal, Food and Health Sciences in Adelaide, is an expert in the role of carbohydrates in bowel health. He is unconvinced by the carbohydrate hypothesis.
"I am not convinced as to the role of FODMAPS overall, but there may be a specific contribution from some of them," he said. "If I eat artichokes, I get cramp and wind. That is a sample of one, so there is need for much more research to identify both mechanism and therapy in a representative group of subjects."
Dr Topping is one of the authors of the March 2014 study investigating the degree of wheat avoidance in adult Australian diets. A survey-based study, the report found that, once confirmed or likely coeliacs were eliminated, just over 7 per cent of Australians – about 1 million people – consciously decide to take wheat out of their kitchens.
The study, published in the journal Public Health Nutrition, yielded some very curious results. Almost three times more women than men reported partially or completely avoiding wheat. More than half of wheat avoiders also avoided dairy products. Most avoiders made their choice based on self-diagnosis, and most reported that they tended to trust alternative health practitioners more than GPs.
Professor Gibson's studies also found that women were more likely than men to report NCGS symptoms. This might indicate only that women are generally more aware of health issues and thus more likely to volunteer to take part in studies.
Whether there is any physiological link between wheat and dairy intolerance is unclear, but one of the South Australian researchers – Adelaide University psychologist Professor Philip Mohr – suggested a different explanation.
"My best guess is that it's somehow related to the way in which we make decisions as humans," he said.
"We make associations which allow us to make decisions quickly – so we might divide food into classes that are fundamentally good or bad.
"There’s a lot of information about wheat and dairy in circulation. They tend to feature as 'baddies' and are much criticised on naturopath websites. There are also a lot of products marketed as gluten-free and lactose-free so people might encounter those kind of messages – and these may set up the tendency to avoid."
The Adelaide study revealed that most people who chose to avoid wheat did so as a result of self-diagnosis. Others did so on the advice of alternative health therapists, some others as a result of consulting dieticians, and only very few after seeing a proper doctor.
This might indicate that wheat-free diets are driven by alt-health ideologies. It might equally, however, indicate a poor understanding of gut-health issues among GPs.
"One thing we have observed in follow-up interviews is a number of people were found to be following the complementary medicine path because conventional medicine was unable to explain their symptoms," Professor Mohr said.
Professor Gibson's team also noted that while relatively few cases of presumed NCGS were diagnosed by medical practitioners, a number of GPs concerned failed to adequately investigate other possible causes, including coeliac disease itself.
Significant differences of opinion exist between the Monash-Leuven and CSIRO-Adelaide University research teams, although both camps conclude that NCGS is very probably a misnomer. Whether wheat-avoidance is fad-driven or factual in the main, the big question is: does it actually matter?
From one perspective, a gluten-free diet for those who don’t actually need one might have some health advantages. "What is so wrong with being gluten-free?" Dr Biesiekierski asked. "Especially given reducing gluten undoubtedly results in the reduction of most, if not all, processed foods, replacing their intake with fresh fruit and vegetables."
Dr Biesiekierski, however, agreed with the other scientists active in the field that going gluten- or wheat-free without proper medical advice could have serious and long-term consequences.
"There seems to be a high degree of self-diagnosis, which appears to derive from a lack of understanding by GPs coupled with mistrust on the part of the patient," Dr Topping said. "One priority is for a greater medical and dietetic awareness of the issue. There is also the risk of avoiders seeking advice from people with very limited scientific and clinical training."
All the researchers expressed strong fears that going gluten-free before seeking medical advice can lead to coeliac disease staying undiagnosed. The condition cannot be identified unless there is gluten present in the body.
"Our main message is that before starting a gluten-free diet it's very important to see a doctor," said Coeliac Victoria executive officer Jane Davies. "Coeliac disease has to be ruled out."
Many coeliacs, who have no option but to avoid gluten, look on in bewilderment at people who choose to do so without medical reason.
"The gluten-free diet is markedly restrictive, presents challenges when eating at places other than home and can be two to three times more expensive than that of a standard diet," Dr Biesiekierski said.
"It can also be nutritionally inadequate, especially in fibre and B-vitamins. Long-term restrictive diets, particularly avoidance of wheat- and gluten-based products, are likely to have health implications given their important role in bowel health."