Dietary copper to zinc ratio intake and irritable bowel syndrome risk: A large-scale prospective cohort study from UK Biobank

Studies have suggested that dietary copper and zinc intake 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 to zinc (Cu/Zn) ratio intake 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 was <1.5 mg/day and zinc intake was <10 mg/day, the risk of IBS significantly decreased with increasing copper and zinc intakes (hazard ratio [HR] copper, 0.791, 95% CI, 0.647-0.967; HR zinc, 0.967, 95% CI, 0.937-0.998). No significant association was found when copper intake was ≥1.5 mg/day and zinc intake was ≥10 mg/day. Subgroup analysis suggested a moderate increase in zinc intake was more helpful for preventing IBS in participants younger than 60 years old. Moderately increasing dietary zinc intake and maintaining dietary copper and Cu/Zn ratio within a reasonable range may be beneficial in reducing IBS incidence.