Food processing and risk of inflammatory bowel disease: A systematic review and meta-analysis

Background & Aims: Several studies have been published on the association between food processing and risks of Crohn's disease (CD) and ulcerative colitis (UC), with some variability in results. We performed a systematic literature review and meta-analysis to study this association. Methods: From PubMed, Medline, and Embase until October 2022, we identified cohort studies that studied the association between food processing and the risk of CD or UC. Risk of bias of the included studies was assessed by the Newcastle-Ottawa scale. We computed pooled hazard ratios (HRs) and 95% confidence intervals (CIs) using random-effects meta-analysis based on estimates and standard errors. Results: A total of 1,068,425 participants were included (13,594,422 person-years) among 5 cohort studies published between 2020 and 2022. Four of the 5 included studies were scored as high quality. The average age of participants ranged from 43 to 56 years; 55%–83% were female. During follow-up, 916 participants developed CD, and 1934 developed UC. There was an increased risk for development of CD for participants with higher consumption of ultra-processed foods compared with those with lower consumption (HR, 1.71; 95% CI, 1.37–2.14; I² = 0%) and a lower risk of CD for participants with higher consumption of unprocessed/minimally processed foods compared with those with lower consumption (HR, 0.71; 95% CI, 0.53–0.94; I² = 11%). There was no association between risk of UC and ultra-processed foods (HR, 1.17; 95% CI, 0.86–1.61; I² = 74%) or unprocessed/minimally processed foods (HR, 0.84; 95% CI, 0.68–1.02; I² = 0%). Conclusions: Higher ultra-processed food and lower unprocessed/minimally processed food intakes are associated with higher risk of CD but not UC.