An Australian study from Monash University in Victoria, although small, sheds a bit more murky light on non-celiac gluten sensitivity (NCGS). The authors have previously published results suggesting that gluten is triggering the physiologic response in patients with irritable bowel syndrome who improve when they discontinue wheat and other gluten-containing foods—this is the emerging definition of NCGS. We recently reviewed a placebo-controlled study that also suggested gluten as the etiology.
The current study suggests that the real culprit might be fermentable, oligo-, di-, mono-saccharides and polyols (FODMAPs) that are found in wheat and other foods and form gas that may be causing symptoms for some of these people.
We’re probably going to be hearing more about FODMAPs, which are mostly short-chain carbohydrates, in the coming years. They’re found in high concentration in wheat and rye, so their presence will confound gluten effects in any trial or anecdotal series reporting problems related to bread or pasta intake. They’re found in other foods as well, including milk, legumes, cashews, pistachios, asparagus, artichokes, sweet corn, onions, garlic, celery, apples, pears, mango, watermelon, nectarines, peaches, and plums (see the Monash University low-FODMAP diet). FODMAPs are poorly absorbed in normal persons, and the result is fermentation in the gut, with resultant gas formation, bloating, and abdominal distention. In primary care practices, these are symptoms that can prompt an office visit for some patients.
The current study suggests that previous work, including well-designed studies linking placebo-controlled gluten intake with symptoms, may have been showing results of sensitivity to FODMAPs consumed before study entry. To tease out the effect, the current study put 37 subjects with NCGS on a low-FODMAP diet for 2 weeks, and then completed a double-blind crossover trial with 3 groups (high-gluten, low-gluten, and control [gluten-free]) diets for a week, followed by a washout period of at least 2 weeks. A 3-day crossover rechallenge with gluten was then given to 22 participants. For all participants, GI symptoms significantly improved during reduced FODMAP intake, but gluten-specific effects were observed in only 8% of subjects. During the 3-day rechallenge, symptoms increased by similar levels among groups. The investigators found no evidence of specific or dose-dependent effects of gluten in NCGS patients who are first placed on a low-FODMAP diet.
Even though this study is very small, it is well-designed and can’t be ignored. Gluten and FODMAPs coexist in wheat, and that makes our patients’ anecdotal report of “gluten sensitivity” very difficult to interpret—what they’re really reporting is bread, cookie, cake, and pasta sensitivity. This study suggests that FODMAPs may be as important as gluten, or even the primary problem for NCGS patients.
The study did not look at a placebo-control for FODMAP intake, and that obviously is needed before jumping to conclusions. But what’s interesting here is that there may be an interaction between FODMAPs and gluten in wheat-eaters; non-gluten but gas-forming foods may (or may not) be the real culprit. FODMAPs appear in many diets rich in healthful proteins and grains—think non-fat yogurt, whole wheat, legumes, and many of the most common fresh fruits and vegetables. This could affect a lot of people, and there may be easier food-swaps that would effectively curb gas production without forcing 20% of the population onto a gluten-free diet.
Biesiekierski JR, Peters SL, Newnham ED, et al. No effects of gluten in patients with self-reported non-celiac gluten sensitivity after dietary reduction of fermentable, poorly absorbed, short-chain carbohydrates. Gastroenterology. 2013;145:320-328. (Abstract)