Dietary Fiber and Colorectal Cancer Risk: A Nested Case-Control Study Using Food Diaries

Department of Public Health and Primary Care, University of Cambridge, Cambridge CB1 8RN, UK.
Journal of the National Cancer Institute (Impact Factor: 12.58). 05/2010; 102(9):614-26. DOI: 10.1093/jnci/djq092
Source: PubMed


Results of epidemiological studies of dietary fiber and colorectal cancer risk have not been consistent, possibly because of attenuation of associations due to measurement error in dietary exposure ascertainment.
To examine the association between dietary fiber intake and colorectal cancer risk, we conducted a prospective case-control study nested within seven UK cohort studies, which included 579 case patients who developed incident colorectal cancer and 1996 matched control subjects. We used standardized dietary data obtained from 4- to 7-day food diaries that were completed by all participants to calculate the odds ratios for colorectal, colon, and rectal cancers with the use of conditional logistic regression models that adjusted for relevant covariates. We also calculated odds ratios for colorectal cancer by using dietary data obtained from food-frequency questionnaires that were completed by most participants. All statistical tests were two-sided.
Intakes of absolute fiber and of fiber intake density, ascertained by food diaries, were statistically significantly inversely associated with the risks of colorectal and colon cancers in both age-adjusted models and multivariable models that adjusted for age; anthropomorphic and socioeconomic factors; and dietary intakes of folate, alcohol, and energy. For example, the multivariable-adjusted odds ratio of colorectal cancer for highest vs the lowest quintile of fiber intake density was 0.66 (95% confidence interval = 0.45 to 0.96). However, no statistically significant association was observed when the same analysis was conducted using dietary data obtained by food-frequency questionnaire (multivariable odds ratio = 0.88, 95% confidence interval = 0.57 to 1.36).
Intake of dietary fiber is inversely associated with colorectal cancer risk. Methodological differences (ie, study design, dietary assessment instruments, definition of fiber) may account for the lack of convincing evidence for the inverse association between fiber intake and colorectal cancer risk in some previous studies.

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Available from: Christina Catherine Dahm
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    • "Several nutrients such as amino acids, carbohydrates, fatty acids, vitamins, and phytochemicals (curcumin, resveratrol) are indeed known to modulate miRNA expression levels [155, 156]. For instance, intake of dietary fiber is inversely associated with colorectal cancer risk [157]. The microbial anaerobic fermentation of dietary fiber produces short chain fatty acids (such as acetate, propionate, and butyrate) and butyrate, whose bioavailability is reduced in case of low fiber intake, was shown to decrease the expression of several oncogenic miRNAs in HCT-116 (miRs-17, -20a, -20b, -93, -106a, and -106b) [158]. "
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    • "Epidemiological evidence suggests a protective role of dietary fiber against CRC (Dahm and others 2010). This type of fiber can be defined as a heterogeneous group of nondigestible compounds , including fiber (soluble and insoluble), resistant starch, and oligosaccharides such as raffinose, stachyose, and mullein, among others (Escudero and Gonzalez 2006). "

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    • "However, the situation has changed dramatically, with the majority of the global cancer burden now found in low-and medium-resource countries (Boyle and Levin 2008). An inverse association between dietary fiber intake and CRC incidence has been shown in epidemiological studies (Dahm et al. 2010). Additionally, research on in vivo and in vitro models has shown the protective role of pulses, primarily due to the presence of indigestible compounds, such as phenolics (condensed tannins, flavonoids and anthocyanins), total dietary fiber (soluble and insoluble), and other secondary metabolites related to the prevention and/or reduction in chronic degenerative diseases (Bazzano et al. 2001; Beninger and Hosfield 2003; Waldecker et al. 2007). "
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