PubMed/Medline, Excerpta Medica dataBASE (EMBASE) and Scopus were searched in January 2021 in order to retrieve evidence assessing the association between dietary fibre intake and the risk of colorectal adenoma in adults. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used for the reporting of results. Only primary observational studies were included. Publication bias was estimated through the Egger's test and the visual inspection of the funnel plot. Heterogeneity between studies was calculated with I2 statistics. The search strategy identified 683 papers, 21 of which were included in our meta-analysis. Having evaluated a total of 157,725 subjects, the results suggest a protective effect of dietary fibre intake against colorectal adenoma. Effect Size (ES) was [0.71 (95% CI = 0.68-0.75), p = 0.000)]. Moderate statistical heterogeneity (Chi2 = 61.68, df = 23, I2 = 62.71%, p = 0.000) was found. Findings show a statistically significant (p = 0.000) and robust association between a higher intake of dietary fibre and a lower risk of colorectal adenoma, considering both the prevalent and incident risk. Moreover, the meta-regression analysis showed a borderline significant negative linear correlation between the amount of dietary fibre intake and colorectal adenoma. Lastly, we performed a subgroup analysis by sex, showing a higher protective effect for men.
Keywords: adenoma; colorectal; diet; fibre; systematic review.