Abstract
BackgroundEarlier analyses within the EPIC study showed that dietary fibre intake was inversely associated with colorectal cancer risk, but results from some large cohort studies do not support this finding. We explored whether the association remained after longer follow-up with a near threefold increase in colorectal cancer cases, and if the association varied by gender and tumour location.Methodology/Principal FindingsAfter a mean follow-up of 11.0 years, 4,517 incident cases of colorectal cancer were documented. Total, cereal, fruit, and vegetable fibre intakes were estimated from dietary questionnaires at baseline. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models stratified by age, sex, and centre, and adjusted for total energy intake, body mass index, physical activity, smoking, education, menopausal status, hormone replacement therapy, oral contraceptive use, and intakes of alcohol, folate, red and processed meats, and calcium. After multivariable adjustments, total dietary fibre was inversely associated with colorectal cancer (HR per 10 g/day increase in fibre 0.87, 95% CI: 0.79–0.96). Similar linear associations were observed for colon and rectal cancers. The association between total dietary fibre and risk of colorectal cancer risk did not differ by age, sex, or anthropometric, lifestyle, and dietary variables. Fibre from cereals and fibre from fruit and vegetables were similarly associated with colon cancer; but for rectal cancer, the inverse association was only evident for fibre from cereals.Conclusions/SignificanceOur results strengthen the evidence for the role of high dietary fibre intake in colorectal cancer prevention.
Highlights
Inverse associations between dietary fibre intake and colorectal cancer risk have been reported in ecological and case-control studies. [5,6] the evidence from prospective studies has been inconsistent,[7,8,9,10,11,12,13,14,15] with the two largest analyses published to date yielding non-significant associations. [13,14] In both the Pooling Project [13] and NIH (National Institutes of Health)AARP analyses [14], statistically significant inverse associations in age-adjusted models disappeared after multivariable adjustment
Fibre from fruits and vegetables combined was not associated with rectal cancer. This analysis of the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort, after a longer term follow-up of 11 years in which 4,517 cases accrued, further strengthens the evidence that dietary fibre is inversely associated with colorectal cancer risk
The inverse association of total fibre with colorectal cancer risk was of similar magnitude in men and women, and for colon and rectal cancers
Summary
A possible protective association between dietary fibre intake and colorectal cancer was first proposed by Burkitt in 1971. [1] Putative anti-carcinogenic mechanisms of dietary fibre within the bowel include: the formation of short-chain fatty acids from fermentation by colonic bacteria; the reduction of secondary bile acid production; the reduction in intestinal transit time and increase of faecal bulk; and a reduction in insulin resistance.[2,3,4] Inverse associations between dietary fibre intake and colorectal cancer risk have been reported in ecological and case-control studies. [5,6] the evidence from prospective studies has been inconsistent,[7,8,9,10,11,12,13,14,15] with the two largest analyses published to date yielding non-significant associations. [13,14] In both the Pooling Project [13] and NIH (National Institutes of Health)AARP analyses [14], statistically significant inverse associations in age-adjusted models disappeared after multivariable adjustment. Differing adjustments for colorectal cancer risk factors which may confound the dietary fibre relationship (such as dietary folate) has been proposed as a possible explanation for the variable results observed between studies. The aims of the present study were to examine whether the previously observed inverse association persisted after longer follow-up (mean 11 years) and an increased number of colorectal cancer cases (from n = 1,721 to n = 4,517); to provide a more precise estimation of the association by cancer sub-site and fibre food source; and to scrutinise the fibre-colorectal cancer relationship further by examining possible interactions by age, sex, and other lifestyle, anthropometric, and dietary variables. Earlier analyses within the EPIC study showed that dietary fibre intake was inversely associated with colorectal cancer risk, but results from some large cohort studies do not support this finding. We explored whether the association remained after longer follow-up with a near threefold increase in colorectal cancer cases, and if the association varied by gender and tumour location
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