Dietary patterns and colorectal cancer: a multicenter case-control study in an Iranian population

Evidence on the association between dietary patterns (DPs) and colorectal cancer (CRC) is inconclusive. Thus, we aimed to evaluate it in an Iranian population. We analyzed data from a multicenter hospital-based case-control study conducted in Iran during 2017-2020. We derived a posteriori DPs using principal component factor analysis, and used reduced rank regression (RRR) to derive a DP high in unhealthy fats. We estimated adjusted odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for the association between quartiles of DPs and CRC. False discovery rate (FDR)-corrected p-values were computed. We included 865 CRC cases and 3,204 controls in the study. After FDR correction, the Western-type diet (OR_Q4vsQ1 4.15; 95% CI 2.49-6.90; p_trend < 0.001) identified through factor analysis was positively associated with CRC. Similarly, the DP high in unhealthy fats derived using RRR (with high factor loadings for animal products) was associated with CRC (OR_Q4vsQ1 2.14; 95% CI 1.40-3.26; p_trend < 0.001). Results were consistent among CRC subsites and different participants' characteristics, including cigarette and waterpipe smoking and opium use. Our study showed that both a Western-style diet and DP high in unhealthy fats are associated with CRC, suggesting that consumption of unhealthy foods, including those high in trans and saturated fatty acids, should be reduced.