Is dietary cholesterol intake associated with risk of colorectal cancer? An updated systematic review and meta-analysis of observational studies

Background: No meta-analysis is available for the strength and shape of a dose-response relation between cholesterol consumption and colorectal cancer (CRC). Therefore, we conducted a systematic review and dose-response meta-analysis of observational studies to measure the association between dietary cholesterol intake and risk of colorectal cancer in adults. Methods: A literature search was done in PubMed, Scopus, and Google Scholar to identify relevant articles up to April 2021. Summary risk estimate and 95% confidence intervals (CI) were obtained from the random-effects model in the meta-analyses of high vs low intake categories. Besides, dose-response analysis (linear and non-linear) was performed to assess the dose-response relations. Results: Eight prospective cohort publications with 334,483 participants and 2719 CRC cases, and 17 case-control publications with 12,142 cases and 22,176 controls were included. We did not detect an association between high vs low cholesterol intake categories and colorectal cancer in cohort studies: 1.20 (95% CI: 0.95 to 1.53, I-2 = 53.7%, P-heterogeneity = 0.035). We found no dose-response relationship (per100 mg/d increment in the intake or non-linear relationship) of dietary cholesterol and risk of CRC. However, a significant association was seen in case-control studies in both analyses of high vs low intake and dose-response relation. Conclusion: Cholesterol consumption was not associated with colorectal cancer when comparing high and low cholesterol intake categories and assessing dose-response relationship among cohort studies, while case-control studies found such associations. Additional prospective cohort studies are needed to confirm these findings.