Dietary trans fatty acids and risk of colorectal cancer: a systematic review and meta-analysis of observational studies.

Abstract

Although trans fatty acid has been associated with diabetes and cardiovascular disorders, studies gave conflicting results when examined their impact on colorectal cancer (CRC). The present systematic review and meta-analysis aimed to summarize the current evidence regarding the association between dietary and tissue trans fatty acids and the risk of CRC. We searched PubMed/MEDLINE, EMBASE, Scopus, Web of Science (ISI), and Google Scholar without date and language limitation up to May 2022 and included the eligible studies. The quality of included studies was assessed using the Newcastle-Ottawa scale. The overall odds ratios (ORs) were derived using a random-effects model. In assessment of dietary trans fatty acids 18 studies, including eight cohort, 10 case-control, and observational data from one randomized control trial were included. Although Dietary trans fats were associated with higher risk of CRC(OR = 1.093, 95% CI 1.017, 1.176, P = 0.016; I2 = 61.3%), Subgroup analysis by study design yielded an insignificant effect for case-control (OR = 1.152, 95% CI 1.000, 1.328, P = 0.050; I2 = 77.2%) and cohort (OR = 1.027, 95% CI 0.976, 1.081, P = 0.299; I2 = 0%) studies. Although there was no significant association of trans fatty acids with rectal cancer (OR = 1.093, 95% CI 0.984 to 1.215, P = 0.098; I2 = 0%), there was for colon cancer (OR = 1.91, 95% CI 1.062 to 1.335, P = 0.003; I2 = 37.6%).The analysis of four studies that evaluated the relation between tissue trans fat and CRC revealed meaningful result (OR = 0.745, 95% CI 0.619, 0.896, P = 0.002; I2 = 42.6%). While subgroup assessments for colon cancer (OR = 0.804, 95% CI 0.583, 1.109, P = 0.183; I2 = 0%) and plasma trans fatty acids OR = 0.853, 95% CI 0.633, 1.150, P = 0.298; I2 = 0%) were insignificant. Dietary trans fatty acids increased the risk of CRC, whereas tissue trans fatty acids had a protective effect on CRC. Nonetheless, neither type of trans fatty acid increased the risk of colon or rectal cancer; thus, more prospective studies are needed to determine the validity of these associations.