In 2011, Peter Gibson, a professor of gastroenterology at Monash University and director of the GI Unit at The Alfred Hospital in Melbourne, Australia, published a study that found gluten, a protein found in grains like wheat, rye, and barley, to cause gastrointestinal distress in patients without celiac disease, an autoimmune disorder unequivocally triggered by gluten. Double-blinded, randomized, and placebo-controlled, the experiment was one of the strongest pieces of evidence to date that non-celiac gluten sensitivity (NCGS), more commonly known as gluten intolerance, is a genuine condition.
But like any meticulous scientist, Gibson wasn't satisfied with his first study. His research turned up no clues to what actually might be causing subjects' adverse reactions to gluten. ... He resolved to repeat the trial with a level of rigor lacking in most nutritional research. 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 fecal matter would be collected. With this new study, Gibson wasn't messing around.
37 subjects took part, all confirmed not to have celiac disease but whose gastrointestinal symptoms improved on a gluten-free diet, thus fulfilling the diagnostic criteria for non-celiac gluten sensitivity.** They were first fed a diet low in FODMAPs for two weeks (baseline), then were given one of three diets for a week with either 16 grams per day of added gluten (high-gluten), 2 grams of gluten and 14 grams of whey protein isolate (low-gluten), or 16 grams of whey protein isolate (placebo). Each subject shuffled through every single diet so that they could serve as their own controls, and none ever knew what specific diet he or she was eating. After the main experiment, a second was conducted to ensure that the whey protein placebo was suitable. In this one, 22 of the original subjects shuffled through three different diets -- 16 grams of added gluten, 16 grams of added whey protein isolate, or the baseline diet -- for three days each.
Analyzing the data, Gibson found that each treatment diet, whether it included gluten or not, prompted subjects to report a worsening of gastrointestinal symptoms to similar degrees. Reported pain, bloating, nausea, and gas all increased over the baseline low-FODMAP diet. Even in the second experiment, when the placebo diet was identical to the baseline diet, subjects reported a worsening of symptoms! The data clearly indicated that a nocebo effect, the same reaction that prompts some people to get sick from wind turbines and wireless internet, was at work here. ... Gluten wasn't the culprit; the cause was likely psychological. Participants expected the diets to make them sick, and so they did. ...
Consider this: no underlying cause for gluten intolerance has yet been discovered.
--Ross Pomeroy, Real Clear Science, on the stomach irritant above the neck. HT: JFB. See also my earlier post on self-induced gluten intolerance