Healthy eating patterns associated with reduced risk of inflammatory bowel disease by lowering low-grade inflammation: evidence from a large prospective cohort study

Limited epidemiological evidence exists regarding the role of healthy eating patterns in reducing the risk of Crohn's disease (CD) and ulcerative colitis (UC). This study aimed to investigate the association between adherence to four established healthy eating patterns and subsequent CD or UC risk, and further examined whether these associations are linked to anti-inflammatory mechanisms. We conducted a prospective cohort study of 197,391 participants from the UK Biobank who completed at least one dietary questionnaire and were free from inflammatory bowel disease or cancer at baseline. Four dietary patterns were assessed, including Alternate Mediterranean Diet (AMED), Healthy Eating Index 2015 (HEI-2015), Healthful Plant-based Diet Index (HPDI), and EAT-Lancet. Cox proportional models with restricted cubic splines were applied to explore the associations. The potential role of low-grade inflammation in these associations was examined through mediation analysis. During 2,193,436 person-years follow-up, 260 CD and 601 UC cases were identified. Higher AMED and HEI-2015 scores were associated with a reduced risk of CD but no UC, with no evidence against nonlinearity. These associations remained consistent across multiple sensitive and subgroup analyses. For dietary components, the fruits and monounsaturated fatty acids: saturated fatty acids ratio in AMED, and total fruits, total protein foods and fatty acid in HEI-2015 were linked to a decreased CD risk. Both diets were also associated with lower plasma inflammation biomarkers. Mediation analysis indicated that 7.66% and 13.40% of the reductions in CD risk attributed to AMED and HEI-2015 diets, respectively, were mediated by low-grade inflammation scores. Higher adherence to AMED and HEI-2015 might significantly reduce CD risk, partly due to their anti-inflammatory properties.