Gluten intake and its possible relationship with pain, skin symptoms, and mental health in the Spanish population: an observational study

Introduction Gluten is one of the most widely consumed protein complexes in Western diets, and knowing how much of it is habitually eaten is a prerequisite for interpreting the dose–response evidence on gluten-related disorders, for defining the exposure levels used in gluten challenge studies, and for placing the growing trend of voluntary gluten avoidance in context. No such estimate has been published for the Spanish general population. Methods We conducted a cross-sectional observational study to estimate mean daily gluten intake and examine its association with stress, depression, anxiety, chronic pain, sleep quality, and skin symptoms in 526 adults (85.0% women; median age 40.50 years; median BMI 22.81 kg/m 2 ) free of celiac disease or gluten intolerance, recruited via an online survey. Gluten intake was estimated with an ad hoc food frequency questionnaire applying the Osborne method. Results Mean intake in this predominantly female sample was 11.14 10.67 g/day (range: 0–82.40 g/day), higher in men (15.46 g/day) than in women (10.38 g/day) and in younger age groups. Participants reporting skin problems (34.98%) consumed significantly more gluten ( p = 0.022), though the effect size was small (Cohen’s d = −0.057). No significant difference emerged between those with and without chronic pain ( p = 0.25). Gluten intake showed weak but statistically significant positive correlations with stress (r = 0.140), anxiety (r = 0.100), depression (r = 0.172), and insomnia (r = 0.141). Discussion These findings provide the first available estimate of gluten consumption in Spain and suggest a possible role of dietary gluten in extra intestinal symptomatology among non-celiac individuals. They must, however, be read with caution: women accounted for 85.0% of respondents and 57.4% of the sample was aged 35–49 years, so the values reported here describe a predominantly female, middle-aged convenience sample and cannot be taken as a nationally representative reference value for the Spanish population. Intake was also not adjusted for total energy intake, and gluten co-occurs with fructans in the same wheat-based foods, so the weak associations observed cannot be attributed specifically to gluten.