Dietary copper, zinc, copper/zinc ratio intakes and irritable bowel syndrome risk: a large-scale prospective cohort study from UK Biobank

Studies have suggested that dietary copper and zinc intakes may be associated with irritable bowel syndrome (IBS), however, prospective evidence is lacking. This study aimed to prospectively investigate the relationship between dietary copper, zinc, and copper/zinc (Cu/Zn) ratio intakes and the development of IBS in a long-term cohort. A total of 175,421 participants in the UK Biobank without IBS at baseline were included. Dietary intake was assessed by the Oxford WebQ. New-onset IBS was identified using ICD-10 codes (K58). Cox proportional hazard models were applied. During a median follow-up of 13.3 years, 2240 individuals were newly diagnosed with IBS. Copper, zinc, and Cu/Zn ratio intakes all showed U-shaped relationships with IBS incidence. When copper intake <1.5 mg/day and zinc intake <10 mg/day, the risk of IBS significantly decreased with increasing copper and zinc intakes [HR copper (95%CI), 0.791(0.647,0.967); HR zinc (95%CI), 0.967(0.937,0.998)]. No significant association was found when copper intake ≥1.5 mg/day and zinc intake ≥10 mg/day. Subgroup analysis suggested a moderate increase in zinc intake was more helpful for preventing IBS in < 60-year-old participants. Moderately increasing dietary zinc intake and maintaining dietary copper and Cu/Zn ratio in a reasonable range is beneficial in reducing IBS incidence.