Dietary fiber intake and risk of colorectal cancer: a pooled analysis of prospective cohort studies.
BACKGROUND
Inconsistent findings from observational studies have continued the controversy over the effects of dietary fiber on colorectal cancer.


OBJECTIVE
To evaluate the association between dietary fiber intake and risk of colorectal cancer.


METHODS
From 13 prospective cohort studies included in the Pooling Project of Prospective Studies of Diet and Cancer, 725,628 men and women were followed up for 6 to 20 years across studies. Study- and sex-specific relative risks (RRs) were estimated with the Cox proportional hazards model and were subsequently pooled using a random-effects model.


METHODS
Incident colorectal cancer.


RESULTS
During 6 to 20 years of follow-up across studies, 8081 colorectal cancer cases were identified. For comparison of the highest vs lowest study- and sex-specific quintile of dietary fiber intake, a significant inverse association was found in the age-adjusted model (pooled RR = 0.84; 95% confidence interval [CI], 0.77-0.92). However, the association was attenuated and no longer statistically significant after adjusting for other risk factors (pooled multivariate RR = 0.94; 95% CI, 0.86-1.03). In categorical analyses compared with dietary fiber intake of 10 to <15 g/d, the pooled multivariate RR was 1.18 (95% CI, 1.05-1.31) for less than 10 g/d (11% of the overall study population); and RR, 1.00 (95% CI, 0.85-1.17) for 30 or more g/d. Fiber intake from cereals, fruits, and vegetables was not associated with risk of colorectal cancer. The pooled multivariate RRs comparing the highest vs lowest study- and sex-specific quintile of dietary fiber intake were 1.00 (95% CI, 0.90-1.11) for colon cancer and 0.85 (95% CI, 0.72-1.01) for rectal cancer (P for common effects by tumor site = .07).


CONCLUSIONS
In this large pooled analysis, dietary fiber intake was inversely associated with risk of colorectal cancer in age-adjusted analyses. However, after accounting for other dietary risk factors, high dietary fiber intake was not associated with a reduced risk of colorectal cancer.
Park
Yikyung
Y
Department of Nutrition, Harvard School of Public Health, Boston, Mass 02115, USA.
Hunter
David J
DJ
Spiegelman
Donna
D
Bergkvist
Leif
L
Berrino
Franco
F
van den Brandt
Piet A
PA
Buring
Julie E
JE
Colditz
Graham A
GA
Freudenheim
Jo L
JL
Fuchs
Charles S
CS
Giovannucci
Edward
E
Goldbohm
R Alexandra
RA
Graham
Saxon
S
Harnack
Lisa
L
Hartman
Anne M
AM
Jacobs
David R
DR
Kato
Ikuko
I
Krogh
Vittorio
V
Leitzmann
Michael F
MF
McCullough
Marjorie L
ML
Miller
Anthony B
AB
Pietinen
Pirjo
P
Rohan
Thomas E
TE
Schatzkin
Arthur
A
Willett
Walter C
WC
Wolk
Alicja
A
Zeleniuch-Jacquotte
Anne
A
Zhang
Shumin M
SM
Smith-Warner
Stephanie A
SA
D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D004043:Dietary Fiber; D005260:Female; D006801:Humans; D008297:Male; D016016:Proportional Hazards Models; D012306:Risk