Fruits, vegetables, and colon cancer risk in a pooled analysis of 14 cohort studies.
BACKGROUND
Fruit and vegetable intakes have been associated with a reduced risk of colon cancer; however, in more recent studies associations have been less consistent. Statistical power to examine associations by colon site has been limited in previous studies.


METHODS
Fruit and vegetable intakes in relation to colon cancer risk were examined in the Pooling Project of Prospective Studies of Diet and Cancer. Relative risks (RRs) and 95% confidence intervals (CIs) were estimated separately in 14 studies using Cox proportional hazards model and then pooled using a random-effects model. Intakes of total fruits and vegetables, total fruits, and total vegetables were categorized according to quintiles and absolute cutpoints. Analyses were conducted for colon cancer overall and for proximal and distal colon cancer separately. All statistical tests were two-sided.


RESULTS
Among 756,217 men and women followed for up to 6 to 20 years, depending on the study, 5838 were diagnosed with colon cancer. The pooled multivariable RRs (95% CIs) of colon cancer for the highest versus lowest quintiles of intake were 0.91 (0.82 to 1.01, P(trend) = .19) for total fruits and vegetables, 0.93 (0.85 to 1.02, P(trend) = .28) for total fruits, and 0.94 (0.86 to 1.02, P(trend) = .17) for total vegetables. Similar results were observed when intakes were categorized by identical absolute cut points across studies (pooled multivariable RR = 0.90, 95% CI = 0.77 to 1.05 for 800 or more versus <200 g/day of total fruits and vegetables, P(trend) = .06). The age-standardized incidence rates of colon cancer for these two intake categories were 54 and 61 per 100,000 person-years, respectively. When analyzed by colon site, the pooled multivariable RRs (95% CIs) comparing total fruit and vegetable intakes of 800 or more versus less than 200 g/day were 0.74 (0.57 to 0.95, P(trend) = .02) for distal colon cancers and 1.02 (0.82 to 1.27, P(trend) = .57) for proximal colon cancers. Similar site-specific associations were observed for total fruits and total vegetables.


CONCLUSIONS
Fruit and vegetable intakes were not strongly associated with colon cancer risk overall but may be associated with a lower risk of distal colon cancer.
Koushik
Anita
A
Department of Nutrition, Harvard School of Public Health, Boston, MA, USA. anita.koushik@umontreal.ca
Hunter
David J
DJ
Spiegelman
Donna
D
Beeson
W Lawrence
WL
van den Brandt
Piet A
PA
Buring
Julie E
JE
Calle
Eugenia E
EE
Cho
Eunyoung
E
Fraser
Gary E
GE
Freudenheim
Jo L
JL
Fuchs
Charles S
CS
Giovannucci
Edward L
EL
Goldbohm
R Alexandra
RA
Harnack
Lisa
L
Jacobs
David R
DR
Kato
Ikuko
I
Krogh
Vittorio
V
Larsson
Susanna C
SC
Leitzmann
Michael F
MF
Marshall
James R
JR
McCullough
Marjorie L
ML
Miller
Anthony B
AB
Pietinen
Pirjo
P
Rohan
Thomas E
TE
Schatzkin
Arthur
A
Sieri
Sabina
S
Virtanen
Mikko J
MJ
Wolk
Alicja
A
Zeleniuch-Jacquotte
Anne
A
Zhang
Shumin M
SM
Smith-Warner
Stephanie A
SA
D000328:Adult; D000368:Aged; D003110:Colonic Neoplasms / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D005060:Europe / Q000453:epidemiology; D005247:Feeding Behavior; D005260:Female; D005638:Fruit; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009656:North America / Q000453:epidemiology; D016017:Odds Ratio; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D040242:Risk Reduction Behavior; D014675:Vegetables