The effect of gluten in adolescents and young adults with gastrointestinal symptoms: a blinded randomised cross‐over trial

BACKGROUND: The popularity of the gluten‐free diet and sales of gluten‐free products have increased immensely. AIMS: To investigate whether gluten induces gastrointestinal symptoms, measured by self‐reported questionnaires, as well as mental health symptoms in adolescents from a population‐based cohort. METHODS: The eligible participants (n = 273) were recruited from a population‐based cohort of 1266 adolescents and had at least four different gastrointestinal symptoms. Phase one (n = 54) was a run‐in phase where the participants lived gluten‐free for 2 weeks. If they improved they continued to phase 2 (n = 33), a blinded randomised cross‐over trial. Participants were blindly randomised either to start with 7 days of gluten, eating two granola bars containing 10 g of gluten or to 7 days on placebo, eating two granola bars without gluten, followed by the reverse and separated by a 7‐day washout period. The effects of the intervention on gastrointestinal symptoms and mental health symptoms were assessed. RESULTS: In total, 54/273 participants entered the run‐in phase and 35 were eligible for randomization. A total of 33 were randomised and 32 completed the trial. The median age was 20.3 (IQR 19.2–20.9) and 32/33 participants were females. Compared with a placebo, gluten did not induce gastrointestinal symptoms. The difference in the average VAS was −0.01 (95% confidence interval −2.07 to 2.05). Nor did we find a difference in the outcomes measuring mental health. CONCLUSION: Compared with placebo, adding gluten to the diet did not induce gastrointestinal symptoms or worsened mental health in adolescents recruited from a population‐based cohort. The trial registration number is NCT04639921.