Association between dietary fiber and endometrial cancer: a dose-response meta-analysis

Background: Endometrial cancer is the most common female gynecologic cancer in the United States. Excessive and prolonged exposure of the endometrium to estrogens unopposed by progesterone and a high body mass are well-established risk factors for endometrial cancer. Although dietary fiber has been shown to beneficially reduce estrogen concentrations and prevent obesity, its role in endometrial cancer has received relatively little attention. Objective: The objective was to summarize and quantify the current evidence of a role of dietary fiber consumption in endometrial cancer risk and to identify research gaps in this field. Design: We conducted a systematic literature review of articles published through February 2007 to summarize the current evidence of a relation between dietary fiber consumption and endometrial cancer fisk and to quantify the magnitude of the association by conducting a dose-response meta-analysis. Results: Ten articles representing 1 case-cohort study and 9 case-control studies that evaluated several aspects of fiber consumption and endometrial cancer risk were identified through searches in various databases. On the basis of 7 case-control studies, the random-effects summary risk estimate was 0.82 (95% CI: 0.75,0.90) per 5 g/1000 kcal dietary fiber, with no evidence of heterogeneity (I-2 : 0%, P for heterogeneity: 0.55). The random-effects summary estimate was 0.71 (95% CI: 0.59,0.85) for the comparison of the highest with the lowest dietary fiber intake in 8 case-control studies, with little evidence of heterogeneity (12: 20.8%, P for heterogeneity: 0.26). In contrast, the only prospective study that evaluated this association did not find an association. Conclusions: Although the current evidence, based on data from case-control studies, supports an inverse association between dietary fiber and endometrial cancer, additional population-based studies, particularly cohort studies, are needed before definitive conclusions can be drawn.