Systematic review of the prospective cohort studies on meat consumption and colorectal cancer risk: A meta-analytical approach

The relation between meat consumption and colorectal cancer risk remains co ntroversial. In this report, we quantitatively reviewed the prospective obs ervational studies that have analyzed the relation between meat consumption and colorectal cancer. We conducted electronic searches of MEDLINE, EMBASE , and CANCERLIT databases through to the end of June 1999 and manual search es of references from retrieved articles. We used both fixed and random-eff ects meta-analytical techniques to estimate the overall association and to investigate possible sources of heterogeneity among studies. Thirteen studi es were eligible for inclusion in the meta-analysis, Pooled results indicat e that a daily increase of 100 g of all meat or red meat is associated with a significant 12-17% increased risk of colorectal cancer. The marginally s ignificant between-study heterogeneity for all meat and red meat was explai ned by a number of study-level covariates, A significant 49% increased risk was found for a daily increase of 25 g of processed meat. The individual s tudy estimates for processed meat showed no detectable heterogeneity. On th e basis of this quantitative review of prospective studies, the overall ass ociation between meat consumption and risk of colorectal cancer appears to be positive, with marginal heterogeneity between studies. The finding for p rocessed meat and data from experimental studies suggests that it may also be an important predictor of colorectal cancer risk. However, because only a few of the studies reviewed here attempted to examine the independent eff ect of meat intake on colorectal cancer risk, the possibility that the over all association may be confounded or modified by other factors cannot be ex cluded.