Gluten-free food is now outselling all other diet foods and "giving up gluten" is seen as the ultimate in fashionable eating. But a new book by a leading gastroenterologist suggests that having gluten imbalances and being "coeliac light" are very real conditions.
Last month the fashion retailer Zara was forced to withdraw its "Are you gluten-free?" T-shirts after 50,000 people signed a petition accusing the brand of trivialising coeliac disease, an illness that results from an intolerance to gluten in everyday foods.
The disease is symptomatic of what Professor David Sanders, a gastroenterologist at the Royal Hallamshire Hospital in Sheffield, calls the "gluten explosion".
Prof Sanders has spent 20 years studying gluten and its effects, and has published a book based on his latest findings.
In population-based studies, he has discovered increasing numbers cutting out gluten because they may have been diagnosed with coeliac disease. Or they may have tested negative to coeliac disease, but still experience "gluten sensitivity", with symptoms such as diarrhoea, constipation and bloating, as well as mouth ulcers, depression and fatigue.
Others are cutting gluten because it's fashionable.
"There are people avoiding gluten without ever having had any symptoms from eating it," he says.
Prof Sanders calls these "lifestylers", inspired by a growing roll-call of gluten-free celebrities, including Gwyneth Paltrow, Victoria Beckham, Michael Douglas and Miley Cyrus, and a collection of bestselling US books linking gluten with everything from obesity to dementia.
"Coeliac disease and gluten sensitivity are very real problems - and they're increasing - but we need to separate scientific facts from hype," he says.
The gluten explosion
Research from Bord Bia shows that the incidence of people buying gluten-free foods in Ireland has risen from 6pc in 2010 to 26pc in 2014. One in four shoppers are buying gluten-free bread, but just a minority of those has any proven intolerance.
The Coeliac Society of Ireland reckons that nine out of 10 Irish 'free from' purchasers are opting for gluten-free living from choice rather than necessity. Its popularity means the 'free from' grocery market in Ireland is now worth approximately €33m. Food intolerance shopping is forecast to reach sales of €40m by 2020.
Martin Healy, founder of the Fitzwilliam Foodtest clinic, says 1pc of the Irish population suffers from coeliac disease.
"The incidence in Ireland is higher than anywhere else in Europe and no one has ever come up with a reason or explanation for this high incidence," he reveals.
Although more cases are presenting, Healy doesn't believe the disease is becoming more common.
"I don't think the condition is rising," he explains. "It is just that people, doctors included, are more aware of it now and people with gut issues are routinely screened for this disease. Diagnosis is much more freely available."
But he does fear that there could still be many more people not diagnosed with coeliac disease but suffering from an undiagnosed gluten intolerance.
"We do approximately 100 food intolerance tests per week and our test checks for gluten intolerance, sometimes referred to as 'non-coeliac gluten intolerance'.
"Our findings are that 20pc of the population suffer from this misunderstood and misdiagnosed problem. Someone suffering with gluten intolerance but tested for coeliac disease will come back with a 'normal' test result, yet gluten intolerance causes all the same chronic symptoms as coeliac disease but at a slightly lesser intensity. It means 20pc of the population is potentially walking around with symptoms associated with gluten sensitivity but going totally undiagnosed."
Coeliac disease or something else?
With coeliac disease, the immune system recognises gluten as an invader and produces antibodies to fight it. Biopsies show the inside of the bowel is flat because gluten has damaged the villi that protrude from the lining of the intestine and are responsible for the absorption of nutrients.
But Prof Sanders's team also found a much larger proportion of people - 13pc - who had tested negative to coeliac disease (diagnosis takes place after a blood test and gastroscopy to look at the state of the bowel), but still reported symptoms after eating gluten.
This condition, known as non-coeliac gluten sensitivity (NCGS), doesn't have a set of biomarkers doctors look for in the blood in the same way that coeliac disease does, but is made through a diagnosis of exclusion after a specialist has ruled out coeliac disease.
"If it is coeliac disease, there is a 10pc family risk, so your first-degree relatives will have to be tested, too," he says. "But if it's not, a specialist can rule out other malabsorption conditions. The key is to not go on a gluten-free diet without ruling out coeliac disease first."
While there is currently no test for NCGS, its symptoms are real.
"I get patients and their coeliac tests were negative but their symptoms are very real and fascinatingly diverse - many report a foggy mind, but also anxiety, nausea, skin problems, dizziness or itchiness," says Prof Sanders.
"The one single feature that was consistent was that when they ate gluten, it was a very unpleasant experience. Twenty years ago we didn't know much about coeliac disease and now we do, but we still don't know enough about NCGS, which I call 'coeliac light'.
"We can't dismiss these people just because the medical community hasn't yet caught up. We need to understand it better."
Do the gluten maths
Ask a typical lifestyler why they've given it up and few will even know what gluten is. A protein found in wheat, barley and rye, gluten is made up of two protein groups, gliadin and glutenin. It's the stuff that makes bread springy and light, and is added to foods such as stock cubes, soy sauce, beer, biscuits, cakes and even chocolate.
Indeed, one of the reasons for the "explosion" in cases of coeliac disease and NCGS, says Prof Sanders, is the fact that "gluten is everywhere".
Although new EU labelling regulations make it mandatory to state on a label that a food contains gluten, manufacturers are not compelled to say how much. Prof Sanders would one day like gluten percentages or grams to be listed along with salt and sugar on food labels.
"Our consumption of gluten is far greater than we are aware," he says. "Food manufacturers love it because it gives food texture and they put it in everything - processed meals, sweets, medicines, everything."
Studies have shown that the more someone is exposed to gluten, the more likely they are to develop intolerance, he says, pointing to a rise in incidence of coeliac disease in China and the subcontinent.
"As the diets become more Westernised, and pizza, bread and pasta replace what was traditionally a rice-based diet, coeliac disease is following."
How gluten attacks
Typical symptoms seen by Prof Sanders are bloating, diarrhoea and constipation, but he is fascinated by how many people report having a foggy mind after eating gluten.
One bestselling book, Grain Brain, by US neurologist Dr David Perlmutter, explores the effects of gluten on the mind. Although Prof Sanders dismisses it as "sensationalist", he concedes that the evidence for gluten's effects on other areas of the body - the brain and the skin - is compelling.
"When the immune system recognises gluten as an invader, it might respond by making different types of an antibody called tissue transglutanimase (TTG)," he says.
"People can develop skin problems, gut problems such as irritable bowel syndrome and brain symptoms. One person's immune system will respond in a different way to the next."
Look at people with coeliac disease and parts of their brains can be affected, especially the areas that affect balance, he says.
"But this can be arrested and improved on a gluten-free diet."
Likewise, studies in Denmark found that anti-gluten antibodies, glycans, are prevalent in people with psoriasis.
"Researchers put them on a gluten-free diet and found an improvement in their psoriatic skin scores," he says.
Gluten has also been implicated in problems such as dementia and eczema, but according to Prof Sanders, "the evidence isn't quite there yet".
© Daily Telegraph