Red and processed meat intake and risk of colorectal adenomas: a systematic review and meta-analysis of epidemiological studies

Background Current evidence indicates that red and processed meat intake increases the risk of colorectal cancer; however, the association with colorectal adenomas is unclear. Objective To conduct a systematic review and meta-analysis of epidemiological studies of red and processed meat intake and risk of colorectal adenomas as part of the Continuous Update Project of the World Cancer Research Fund. Design PubMed and several other databases were searched for relevant studies from their inception up to 31 December 2011. Summary relative risks (RRs) were estimated using a random effects model. Results Nineteen case–control studies and seven prospective studies were included in the analyses. The summary RR per 100 g/day of red meat was 1.27 (95 % CI 1.16–1.40, I2 = 5 %, n = 16) for all studies combined, 1.20 (95 % CI 1.06–1.36, I2 = 0 %, n = 6) for prospective studies, and 1.34 (95 % CI 1.12–1.59, I2 = 31 %, n = 10) for case–control studies. The summary RR per 50 g/day of processed meat intake was 1.29 (95 % CI 1.10–1.53, I2 = 27 %, n = 10) for all studies combined, 1.45 (95 % CI 1.10–1.90, I2 = 0 %, n = 2) for prospective studies, and 1.23 (95 % CI 0.99–1.52, I2 = 37 %, n = 8) for case–control studies. There was evidence of a nonlinear association between red meat (pnonlinearity