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I lived in the Blue Mountains West of Sydney for several years, an area which gave every impression of being the food fad capital the world. I remember having coffee in a cafe where the salt and-pepper containers on the table were labelled "All Natural", neither cane sugar nor aspartame were available to sweeten the coffee and the gluten-free scones disintegrated into a pile of crumbs at the first attempt to break them in half. My local pub bistro advertised gluten-free steak.
Gluten intolerance seems to be the dietary fad du jour, and there is a specific medical condition related to this intolerance. To quote the Royal Australian College of General Practitioners:
"Coeliac disease (CD) is an autoimmune condition affecting at least 1% of the population, many of whom remain undiagnosed. It is characterised by chronic inflammation of the small-intestinal mucosa and triggered by eating gluten. It is challenging to diagnose because of the many and varied ways in which it may present."
You might note the RACGP says this condition affects "at least 1% of the population", but there have been estimates (usually in the tabloid media) that the incidence could be as high as 50%. There is a thriving industry among alternative medicine practitioners and "health food" outlets offering both solutions to and protection from the problem. (As a disclaimer, I have a couple of friends who have been medically diagnosed with coeliac disease who appreciate the fact that it is now easier for them to avoid gluten when eating out or buying food to eat at home, but they get annoyed by the faddishness and quackery.)
So what is the science? Is gluten intolerance something that really only affects about one percent of the population or is it a widespread public health problem like obesity or Type II diabetes?
In 2011, Peter Gibson at Monash University performed a small but scientifically sound study which found gluten-containing diets can cause gastrointestinal upset in people without coeliac disease. It was called "non-coeliac gluten sensitivity". It seemed at the time the people avoiding gluten in their diet were probably doing the right thing even if they had not been diagnosed with coeliac disease. Maybe the real figure was 50% after all.
Gibson had some doubts about this research. The sample for the study was small (34 subjects, but large enough to find a result) but the real problem is that gluten occurs in a very wide range of food products. It is a mixture of proteins found in wheat as well as the hybrid varieties such as spelt and triticale and other similar cereals such as barley, rye and oats. Is actually quite hard to avoid, just as carbohydrates can be difficult to avoid for people with diabetes. If the intolerance was actually as widespread as the study found then a lot more people would be sick.
A new study was done using much better controls to test the findings of the earlier research. To quote a summary on the website Real Clear Science:
"Subjects would be provided with every single meal for the duration of the trial. Any and all potential dietary triggers for gastrointestinal symptoms would be removed, including lactose (from milk products), certain preservatives like benzoates, propionate, sulfites, and nitrites, and fermentable, poorly absorbed short-chain carbohydrates, also known as FODMAPs. And last, but not least, nine days' worth of urine and faecal matter would be collected. With this new study, Gibson wasn't messing around."
The conclusion published for this second study said:
"In a placebo-controlled, cross-over rechallenge study, we found no evidence of specific or dose-dependent effects of gluten in patients with NCGS placed [on] diets low in FODMAPs"
It seems then the problem isn't gluten per se, where the intestinal walls are damaged as in coeliac disease, but that the bloating and discomfort the some people feel seem to be due to the fermentation products of the virtually indigestible FODMAPS. This of course doesn't mean that the discomfort that people feel after eating cereal products is imaginary, but it points to a totally different culprit. There may be a large nocebo effect that causes people to blame gluten for their problems and allows them to subjectively minimise the symptoms when they think they are eating gluten free food, but maybe gluten isn't the villain after all.
The lesson from this however is not really about whether gluten is good or bad for you. It's about the self-correcting nature of science. Something was found, further research was done and it was found that the original findings may have been a mistake.
Nobody should ever be ashamed of saying "I was wrong" or "I don't know", because the next step is saying "Let's find out". And that's what science is all about.
This article was published as the Naked Skeptic column in the December 2016 edition of Australasian Science
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