Dietary fat is associated with increased inflammatory bowel disease onset risk: a systematic review and dose-response...

The association between dietary fat and the risk of inflammatory bowel disease (IBD) onset, especially for specific fatty acids, is controversial. We aimed to examine and quantify the association between dietary fat and IBD onset risk.

PubMed, Embase and Web of Science were searched for studies that reported estimates of IBD onset risk up to January 2025. Relative risks (RRs) and 95% CIs were pooled, and subgroup analyses, meta-regression, and evaluations of dose‒response relationships were conducted.

High fat intake (RR = 1.24, 95% CI = 1.03-1.49) was modestly associated with increased IBD onset risk. Subgroup analyses and meta-regression indicated that Asian (RR = 2.15, 95% CI = 1.46-3.16, Psubgroup < 0.01), high-male-proportion (RR = 1.91, 95% CI = 1.32-2.78, Psubgroup < 0.01) and young (RR = 2.67, 95% CI = 1.80-3.96, Psubgroup < 0.01) populations were more susceptible to fat-associated IBD, and positive dose‒response associations were also confirmed in these populations. Both the highest-versus-lowest and dose‒response analyses revealed that polyunsaturated fatty acids (PUFAs) (RR = 1.34, 95% CI = 1.10-1.63; Pnonlinearity < 0.05; per 10 g/day RR = 1.39) and cholesterol (RR = 1.52, 95% CI = 1.09-2.12; Pnonlinearity  = 0.03; per 0.1 g/day RR = 1.17) were associated with increased IBD onset risk, whereas long-chain n-3 PUFA (LCN-n-3, RR = 0.74, 95% CI = 0.58-0.94) intake and a high n3/n6-PUFA ratio (RR = 0.76, 95% CI = 0.59-0.98) might be associated with decreased IBD risk.

Higher fat intake might be modestly associated with increased IBD onset risk, particularly for PUFA and cholesterol, whereas LCN-n-3 and a high n3/n6-PUFA ratio may offer protective effects against IBD onset.