17 February 2020

Avoiding ‘demon’ gluten for all the wrong reasons

Allergies Nutrition

Many Australians are subjecting themselves to a gluten-free diet for no good reason, according to new research, seeking symptom relief and general health benefits that would be better sought elsewhere.

A team led by Dr Michael Potter at the University of Newcastle in NSW surveyed Newcastle and Gosford residents in 2015 and 2018 to estimate the incidence and resolution of self-reported non-coeliac wheat sensitivity, and the prevalence of gluten avoidance.

More than 1300 people responded to both surveys, which included questions on abdominal symptoms, medical diagnoses and, in 2018 only, on gluten/wheat avoidance.

They found about 14% of respondents reported wheat sensitivity without coeliac disease (coeliac affects about 1% of the population), but data linkage showed they weren’t the same 14% both times.

Almost a quarter (24%) of respondents in the second survey reported at least partially avoiding wheat/gluten, while 3.8% avoided it completely. The most common reasons were general health and weight loss.

Previous research shows the diet can result in significant deficiencies, including in fibre, micronutrients including vitamins D, B12 and folate, and minerals including zinc, iron, magnesium and calcium.

Because starches and fats often substitute for gluten, the diet also has a high glycaemic index and can increase cardiovascular and obesity risk.

Coeliac specialist Associate Professor Jason Tye-Din, a researcher at the Walter and Eliza Hall Institute and Melbourne University and a clinician gastroenterologist at Royal Melbourne Hospital, said the study highlighted the need for more research and more clinical investigation of abdominal symptoms.

While the study had some limitations (self-report, potential ascertainment bias, failure to distinguish between gluten and wheat), Professor Tye-Din said it was “overall a really useful study”.

He said gluten had been demonised and going gluten-free for health reasons was not backed by evidence.

“We have good data to say that the gluten-free diet is a crucial medical treatment for people with coeliac disease,” he said. “But to say removing wheat or gluten from the diet will help with general health is actually not supported by any good studies.

“There’s emerging population studies that show extreme restriction of gluten from the diet, which also involves restriction of whole grains, is associated with an increase in cardiovascular issues like heart attacks and possibly other metabolic syndromes like diabetes.

“I think people are doing their best, but there is certainly a fad component and I do encourage people not to view the gluten-free diet as a way of losing weight and improving their health and really only to explore that if it’s medically indicated.

“Taking wheat out of the diet is not necessarily an innocuous thing and [those with sensitivities] should be seeing their doctor to try to work out what’s causing their symptoms.”

Professor Tye-Din said many of the respondents claiming sensitivity to wheat or gluten also fit the criteria for irritable bowel syndrome. Their symptoms were more likely caused by the fructans in wheat and would be relieved by a low-FODMAP diet.

He said non-coeliac wheat sensitivity was “a very difficult clinical entity to manage” because there were no diagnostic biomarkers.

The formal diagnosis was through a double-blinded placebo challenge, but that was impractical in a consultation, so doctors had to rely on self-report.

The first step for GPs was to exclude coeliac disease, which could cause infertility, osteoporosis and lymphoma, and was hereditary. Next was to exclude wheat allergy, especially in children. Then GPs should work with a dietician to find out what food triggers the patient had.

The authors also note the links between wheat sensitivity and functional dyspepsia with duodenal eosinophilia, and Professor Tye-Din said more research was needed to understand these phenomena.

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