Two randomized crossover multicenter studies investigating gastrointestinal symptoms after bread consumption in individuals with noncoeliac wheat sensitivity: do wheat species and fermentation type matter?

Many individuals reduce their bread intake because they believe wheat causes their gastrointestinal (GI) symptoms. Different wheat species and processing methods may affect these responses. We investigated the effects of six different bread types (prepared from three wheat species and two fermentation conditions) on GI symptoms in individuals with self-reported non-coeliac wheat sensitivity (NCWS). Two parallel, randomised, double-blind, crossover, multicentre studies were conducted. NCWS individuals, in whom coeliac disease and wheat allergy were ruled out, received five slices of yeast fermented (YF) (study A, n=20) or sourdough fermented (SF) (study B, n=20) bread made of bread wheat, spelt, or emmer in a randomised order on three separate test days. Each test day was preceded by a run-in period of 3 days of a symptom-free diet and separated by a wash-out period of ≥7 days. GI symptoms were evaluated by change in symptom score (test day minus average of the 3-day run-in period) on a 0-100mm visual analogue scale (ΔVAS), comparing medians using the Friedman test. Responders were defined as an increase in ΔVAS of ≥15mm for overall GI symptoms, abdominal discomfort, abdominal pain, bloating and/or flatulence. GI symptoms did not differ significantly between breads of different grains (YF bread wheat median ΔVAS 10.4mm [interquartile range 0.0-17.8mm], spelt 4.9mm [-7.6-9.4mm], emmer 11.0mm [0.0-21.3mm], p=0.267; SF bread wheat 10.5mm [-3.1-31.5mm], spelt 11.3mm [0.0-15.3mm], emmer 4.0mm [-2.9-9.3mm], p=0.144). The number of responders was also comparable for both YF (6 to wheat, 5 to spelt, and 7 to emmer, p=0.761) and SF breads (9 to wheat, 7 to spelt, and 8 to emmer, p=0.761). The majority of NCWS individuals experienced some GI symptoms for at least one of the breads, but on a group level, no differences were found between different grains for either YF or SF breads. ClinicalTrials.gov, NCT04084470(https://classic.clinicaltrials.gov/ct2/show/NCT04084470)