Unless you have been medically diagnosed with coeliac disease or gluten sensitivity, a rigorous new study shows that eating foods containing gluten will cause you no harm, and avoiding these proteins in your diet isn't necessary.
In the first double-blind randomised controlled trial, which is one of the most reliable tests we have today, healthy volunteers who ate gluten-containing flour did not report gastrointestinal symptoms or fatigue.
It's the first time a test like this has relied on healthy volunteers with no history of gut issues (such as irritable bowel syndrome), and it helps to clear up some of the mixed results that have been surfacing in recent years.
Today in the United States, over three million people follow a gluten-free diet, even though some 82 percent have not been diagnosed with health issues that would require this lifestyle change. People cite many reasons for going gluten-free, but "wellbeing" is usually a reigning factor.
According to American market research, 65 percent of the public thinks gluten-free diets are just generally healthier. The new research, along with plenty of other studies, challenges this widespread assumption.
"The benefits of a [gluten free diet] are sold also on the basis of a decreased disease burden, improved cognitive function, weight loss, and 'looking good'," write gastroenterologists Emma Halmos and Peter Gibson from Monash University in an editorial accompanying the study.
"Data to support such notions are missing. In fact, large prospective cohort studies, including the National Health and Nutrition Examination Survey, have shown no risk of gluten contributing to cardiovascular disease or the metabolic syndrome."
The new study is small and short, but its method is tightly controlled and carefully regulated for bias. For over two weeks, 28 volunteers, randomly split into two groups, were asked to follow a gluten-free diet, while also consuming a dose of flour twice a day that equalled either 14 grams of gluten or was entirely gluten free. Not even the researchers were aware of who was receiving which type of flour.
To measure any changes in their abdominal pain, reflux, indigestion, diarrhoea, and constipation, each participant also completed a series of symptom-rating scales before and after the two week test. Their feelings of fatigue were gauged using a visual analogue scale.
In the end, independent analyses between the randomised groups showed no significant differences among healthy patients in any symptoms, including abdominal pain. Overall, only one healthy individual who ate gluten reported diarrhoea, and the authors argue this is likely anomalous.
This suggests that avoiding gluten does not provide any benefits to the average healthy person.
In stark contrast, people with diagnosable problems linked to gluten can have serious issues. A double-blind randomised controlled study on those with non-coeliac gluten sensitivity, for example, found over 90 percent of patients had a clinical relapse during their gluten challenge.
In those with coeliac disease, gluten can actually destroy the lining of the small intestine, and if the damage becomes too much it can lead to osteoporosis, infertility, nerve damage, and seizures.
Such extreme reactions to gluten are quite rare however, occurring in less than one percent of the total US population. A strict, life-long gluten-free diet is therefore required for this small subset of individuals, but the new research suggests that doesn't really apply to anyone else.
"The big question is whether these findings will dampen enthusiasm for the use of a gluten-free diet among the general community," Halmos and Gibsen write, adding that scientifically valid findings have had little influence on beliefs about gluten so far.
There's even some evidence that gluten-free diets can do more harm than good. Previous surveys have shown those with coeliac disease do not consume enough calcium, iron, fibre, folate and thiamine. Another study found people with a lower gluten intake had a higher risk of developing type 2 diabetes.
Given these results, the authors of the new study suggest "there is possibly clinical justification in actively discouraging people from starting it if they have no diagnosable sensitivity."
The research was published in Gastroenterology.