Gastroenterology

Gastroenterology

Volume 146, Issue 3, March 2014, Pages 689-699.e6
Gastroenterology

Original Research
Full Report: Clinical—Alimentary Tract
Dietary Fiber Intake Reduces Risk for Colorectal Adenoma: A Meta-analysis

https://doi.org/10.1053/j.gastro.2013.11.003Get rights and content

Background & Aims

Reports on the association between dietary fiber intake and risk of colorectal adenoma (CRA), the precursor of colorectal cancer, have been inconsistent. We conducted a meta-analysis of case-control and cohort studies to analyze this association.

Methods

We searched the MEDLINE and EMBASE databases to identify relevant studies published through July 2013. A random-effects model was used to estimate summary relative risks (SRRs) and 95% confidence intervals (CIs) for associations between fiber intake and CRA risk. Heterogeneity among studies was assessed using the Cochran Q and I2 statistics.

Results

Our meta-analysis included 20 studies involving 10,948 subjects with CRA. The SRRs of CRA for total dietary fiber were 0.72 (95% CI, 0.63–0.83) in a high- vs low-intake analysis and 0.91 (95% CI, 0.87–0.95) per 10-g/day increase in fiber intake in a dose-response model. Subgroup analyses indicated a significant inverse association between total fiber intake and CRA risk in case-control studies (SRR, 0.66; 95% CI, 0.56–0.77), but not in cohort studies (SRR, 0.92; 95% CI, 0.76–1.10). The SRRs of CRA were 0.84 for fruit fiber (95% CI, 0.76–0.94; n = 6 studies), 0.93 for vegetable fiber (95% CI, 0.84–1.04; n = 6 studies), and 0.76 for cereal fiber (95% CI, 0.62–0.92; n = 9 studies) in high- vs low-intake analyses.

Conclusions

Our findings support the hypothesis that high dietary fiber intake is associated inversely with CRA risk. Further studies with prospective designs that use validated questionnaires and control for important confounders are warranted.

Section snippets

Data Sources and Searches

Two investigators (Q.W.B. and Y.W.S.) independently performed computerized literature searches of the MEDLINE and EMBASE databases to identify relevant studies published through July 2013. The following text and/or medical subject heading terms were used: (1) “food” OR “diet” OR “consumption” OR “dietary” OR “intake” OR “fiber” OR “fibre,” (2) “adenoma” OR “polyp” OR “neoplasm” OR “neoplasia,” (3) “colorectal” OR “colon” OR “rectal” OR “large bowel,” and (4) “risk” OR “incidence” OR

Search Results, Study Characteristics, and Quality Assessment

The search strategy generated 10,578 citations, of which 50 were considered of potential value; the full texts of these publications were retrieved for detailed evaluation (Figure 1). Thirty-three of these 50 articles subsequently were excluded for various reasons, and our review of reference lists led to the inclusion of 3 additional articles. Thus, reports of 20 studies involving 10,948 subjects with CRA were included in the meta-analysis (Supplementary Tables 1 and 2). These studies were

Discussion

The results of this meta-analysis support the hypothesis that dietary fiber intake is associated inversely with the risk of CRA. Analyses of high vs low intake and dose-response models indicated that CRA risk was reduced by 28% and 9% per 10-g/day increase, respectively. No potential for a nonlinear association between dietary fiber intake and CRA risk was detected. Furthermore, we observed significant inverse associations with fruit and cereal fiber intakes, but not with vegetable fiber intake.

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    Conflicts of interest The authors disclose no conflicts.

    Funding Supported by the National Natural Science Foundation of China (no. 81072025).

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