Dietary fat and fatty acids in relation to risk of colorectal cancer

Purpose Epidemiologic evidence for specific types and sources of dietary fat and individual fatty acid with colorectal cancer (CRC) risk remains inconclusive. We aimed to comprehensively examine the associations of intakes of specific types (saturated, monounsaturated, polyunsaturated, and trans) and sources (animal, dairy, and vegetable) of dietary fat and individual fatty acid with CRC risk. Design We prospectively followed 65,550 women from the Nurses' Health Study (1986-2014) and 45,684 men from the Health Professionals Follow-up Study (1986-2014). Dietary intake was assessed every 4 years using food frequency questionnaires. Self-reported CRC cases were confirmed through medical record review. Time-dependent Cox proportional hazards regression was used to estimate the hazard ratios (HRs) for intakes of dietary fats and fatty acids and CRC risk. Results During 2,705,560 person-years of follow-up, 2726 incident CRC cases were confirmed. Intake of monounsaturated fat tended to be positively associated with the risk of CRC (HR comparing extreme quintiles 1.22; 95% CI 1.01, 1.47; p = 0.06 for trend). This positive association was mainly driven by monounsaturated fatty acids from animal sources (MUFA-As) (HR comparing extreme quintiles 1.23; 95% CI 1.02, 1.49; p = 0.02 for trend). The positive association between MUFA-As and CRC was attenuated after adjusting for red and processed meat consumption (HR comparing extreme quintiles 1.17; 95% CI 0.95, 1.44; p = 0.13 for trend). We did not find clear associations between other types and sources of dietary fat or individual fatty acid and CRC risk. Conclusions Higher intake of MUFA-As was associated with higher CRC risk. This could be partly explained by confounding due to other components of red and processed meat.