Associations of dietary fat types (MUFA, PUFA, SFA) and sources (animal, plant) with colorectal cancer risk: A comprehensive systematic review and dose-response meta-analysis of prospective cohort studies

Background and objectives: While dietary fat intake has long been implicated as a risk factor for colorectal cancer, evidence from prospective cohort studies remains inconsistent. Moreover, previous meta-analyses examining the link between dietary fat intake and risk of colorectal cancer have not explored the dose-response relationships. Therefore, the current systematic review and meta-analysis was conducted to assess the dose-response associations of intakes of specific types (MUFA, PUFA and SFA) and sources (animal, plant) of dietary fat with the risk of colorectal, colon or rectal cancer. Methods: A comprehensive literature search of relevant online databases was performed to detect eligible studies until May 2023, identifying 21 prospective cohort studies with a total sample size of 2311,737 participants. The follow-up periods ranged from 7 to 19.4 years, during which 21,125 cases of colorectal, colon or rectal cancer were recorded. Results: Comparing extreme intake levels of total fat revealed the summary relative risk (RR) of 1.05 (95 % CI: 0.96-1.15) for colorectal cancer, 0.99 (95 % CI: 0.87-1.11) for colon cancer, and 1.09 (0.95 % CI: 0.93-1.13) for rectal cancer, indicating no significant association. Neither animal nor plant fat intake was associated with the risk of cancers. While no significant findings were also observed for MUFA or PUFA, the highest versus lowest comparison showed that a high intake of SFA was associated with a reduced risk of both colorectal 0.91 (95 % CI: 0.85-0.99) and colon cancer 0.86 (95 % CI: 0.75-0.98). However, in the non-linear dose-response analysis, the inverse association was seen within a certain range (<40 g/day). Conclusions: These findings suggest that dietary SFA intake, less than 40 g/day, may have a protective effect against colorectal cancer. Further studies are needed to confirm our findings.