No Effects of a Short-Term Gluten-free Diet on Performance in Nonceliac Athletes

Purpose Implementation of gluten-free diets among nonceliac athletes has rapidly increased in recent years because of perceived ergogenic and health benefits. The aim of this study was to investigate the effects of a gluten-free diet (GFD) on exercise performance, gastrointestinal (GI) symptoms, perceived well-being, intestinal injury, and inflammatory responses in nonceliac athletes. Methods Thirteen competitive endurance cyclists ( 8 males, 5 females) with no positive clinical screening for celiac disease or history of irritable bowel syndrome ( mean +/- SD; age, 32 +/- 7 yr; weight, 71.1 +/- 13.4 kg; height, 177.0 +/- 11.8 cm, V. O2max 59.1 +/- 8.0 mLkg-1 min-1) were allocated to a 7- d gluten- containing diet ( GCD) or GFD separated by a 10- d washout in a controlled, randomized, double- blind, crossover study. Cyclists ate a GFD alongside either gluten- containing or gluten- free food bars ( 16 g wheat gluten per day) while habitual training and nutrition behaviors were controlled. During each diet, cyclists completed the Daily Analysis of Life Demand for Athletes ( DALDA) and GI questionnaires ( postexercise and daily). On day 7, cyclists completed a submaximal steady- state ( SS) 45- min ride at 70% W-max followed by a 15- min time trial ( TT). Blood samples were taken preexercise, post- SS, and post- TT to determine intestinal fatty acid binding protein ( IFABP) and inflammatory markers ( cytokine responses: interleukin [ IL] 1 beta, IL- 6, IL- 8, IL- 10, IL- 15, tumor necrosis factor alpha). Mixed effects logistic regression was used to analyze data. Results TT performance was not significantly different (P = 0.37) between the GCD (245.4 +/- 53.4 kJ) and GFD (245.0 +/- 54.6 kJ). GI symptoms during exercise, daily, and DALDA responses were similar for each diet (P > 0.11). There were no significant differences in IFABP (P = 0.69) or cytokine (P > 0.13) responses. Conclusions A short-term GFD had no overall effect on performance, GI symptoms, well-being, and a select indicator of intestinal injury or inflammatory markers in nonceliac endurance athletes.