Above: Image © istockphoto.com/diosmic
It's very trendy to be gluten-free these days. Everyone from celebrities to your next-door neighbour seems to be giving up gluten, a decision made easier by the growing popularity of gluten-free products. The wide range of gluten-free options is great news for people with celiac disease, which affects about 1 in 133 Canadians. But a lot of other people choose to avoid gluten due to “gluten sensitivity” or simply because they think gluten-free diets are healthier.
Did you know? Celiac disease is an abnormal immune response to gluten in the small intestine, which prevents the body from properly absorbing nutrients like proteins, fats, carbohydrates, vitamins, and minerals.
One big factor behind the gluten-free craze is a study published by Australian researchers in 2011. It linked gluten to gastrointestinal symptoms in people who did not have celiac disease. In this study, participants ate a gluten-free diet for two weeks and their baseline symptoms were monitored. In the next phase, all participants continued following the same gluten-free diet for another six weeks. However, during this period, they were also given two bread slices and one muffin per day that either contained gluten (the gluten group) or were gluten-free (the placebo group).
The study found that more subjects in the gluten group experienced gastrointestinal symptoms than in the placebo group. Although the researchers concluded that “non-celiac gluten sensitivity” may exist, they couldn't find a way to explain why.
Unsatisfied with the results of their previous study, the same researchers set out to repeat the experiment, this time controlling more of the variables that could lead to unreliable results. First, the participants were chosen: as with the first experiment, none had celiac disease, but all reported feeling better on a gluten-free diet. Next, meals were carefully prepared to exclude anything that could trigger gastrointestinal symptoms, such as lactose, certain preservatives, and fermentable, poorly absorbed short-chain carbohydrates, also known as FODMAPs (lactose, fructose, fructans, galactans, and polyols). When eaten in excess, FODMAPs can cause gastrointestinal symptoms, and a low-FODMAP diet is often recommended to those with irritable bowel syndrome.
For the first two weeks of the study, all the participants ate a baseline diet low in FODMAPs. Next, they ate one of the following three diets for a week: a high gluten diet (16 grams of gluten per day), a low gluten diet (2 grams of gluten and 14 grams of whey protein isolate per day), or a placebo diet (16 grams of whey protein isolate per day). Each participant went through all of the different diets, never knowing which one they were eating, and there was a two-week period between each diet to make sure there were no leftover symptoms that could confuse the results.
Did you know? Gluten is a protein found in wheat, rye, barley, bulgur, farro, kamut, spelt, and triticale.
Gluten helps food bind together and keep its shape.To verify the results, participants were invited back for a second round of the experiment. This time, they ate diets with 16 grams of added gluten, 16 grams of added whey protein, and a baseline diet (placebo). Once again, all of the participants spent a week on each of the diets.
When the participants ate the baseline diet, they reported an improvement in their symptoms. However, each time they started a new diet, they reported almost exactly the same type and severity of symptoms—such as pain, gas, bloating, and nausea—regardless of whether or not they were eating gluten. In fact, even in the second experiment, when participants ate the gluten-free placebo diet (which was exactly the same as the initial baseline diet), they reported that their symptoms got worse. But these symptoms were not even present when they initially ate the baseline diet!
The results of these experiments strongly suggest that symptoms associated with gluten sensitivity have more of a psychological than a physical cause. In contrast to his first study, Gibson concluded that there was no evidence for gluten being the cause of any gastrointestinal symptoms.
But even if it isn't really healthier or doesn't really make you feel better, is there any harm in going gluten-free? Going gluten-free means saying no to a lot of foods which contain essential vitamins, minerals, and fibre, and maybe even missing out on special foods like birthday cake and pizza. Although it is great that gluten-free options exist for those who truly need them, the rest of us shouldn't place so much importance on avoiding gluten.
No Effects of Gluten in Patients With Self-Reported Non-Celiac Gluten Sensitivity After Dietary Reduction of Fermentable, Poorly Absorbed, Short-Chain Carbohydrates (2013)
J. R. Biesiekierski, S. L. Peters, E. D. Newnham, O. Rosella, J. G. Muir & P. R. Gibson, Gastroenterology 145
Gluten Causes Gastrointestinal Symptoms in Subjects Without Celiac Disease: A Double-Blind Randomized Placebo-Controlled Trial (2011)
J. R. Biesiekierski, E. D. Newnham, P. M. Irving, J. S. Barrett, M. Haines, J. D. Doecke, S. J. Shepherd, J. G. Muir & P. R. Gibson, American Journal of Gastroenterology 106
Link to abstract. A subscription is required to view the full text.
The first and second studies by Australian researchers into the existence and nature of non-celiac gluten sensitivity.
The Truth About Gluten (2011)
Peter Jaret, WebMD.com
Discussion of the need for and merits of gluten-free diets.