Journal of the National Cancer Institute Advance Access published online on September 25, 2007
JNCI Journal of the National Cancer Institute, doi:10.1093/jnci/djm155
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© The Author 2007. Published by Oxford University Press.
ARTICLES |
Fruits, Vegetables, and Colon Cancer Risk in a Pooled Analysis of 14 Cohort Studies
Affiliations of authors: Departments of Nutrition (AK, DJH, ELG, SASW), Biostatistics (DS), and Epidemiology (DJH, DS, JEB, ELG, SMZ, SASW), Harvard School of Public Health, Boston, MA; The Center for Health Research, Loma Linda University School of Medicine, Loma Linda, CA (WLB, GEF); Department of Epidemiology, Maastricht University, Maastricht, The Netherlands (PAvdB); Epidemiology and Surveillance Research, American Cancer Society, Atlanta, GA (EEC, MLM); Channing Laboratory (EC, CSF, ELG, DJH) and Division of Preventive Medicine (JEB, SMZ); Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA; Department of Social and Preventive Medicine, University at Buffalo, State University of New York, Buffalo, NY (JLF); Department of Cancer Prevention and Population Sciences, Roswell Park Cancer Institute, Buffalo, NY (JRM); Department of Adult Oncology, Dana-Farber Cancer Institute, Boston, MA (CSF); Department of Food and Chemical Risk Analysis, TNO Quality of Life, Zeist, The Netherlands (RAG); Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, Minneapolis, MN (LH, DRJ); Karmanos Cancer Institute/Department of Pathology, Wayne State University School of Medicine, Detroit, MI (IK); Nutritional Epidemiology Unit, National Cancer Institute, Milan, Italy (VK, SS); Division of Nutritional Epidemiology, National Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden (SCL, AW); Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD (MFL, AS); Department of Public Health Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada (ABM); Department of Epidemiology and Health Promotion, National Public Health Institute, Helsinki, Finland (PP, MJV); Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY (TER); Department of Environmental Medicine, Division of Epidemiology, New York, NY (AZJ)
Correspondence to: Anita Koushik, PhD, Department of Social and Preventive Medicine, Centre de recherche du CHUM, University of Montreal, 3875 rue Saint-Urbain, Third floor, Montreal, QC H2W 1V1, Canada (e-mail: anita.koushik{at}umontreal.ca) or Stephanie Smith-Warner, Department of Nutrition, Harvard School of Public Health, 665 Huntington Ave, Boston, MA 02115 (e-mail: pooling{at}hsphsun2.harvard.edu).
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 756217 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, Ptrend = .19) for total fruits and vegetables, 0.93 (0.85 to 1.02, Ptrend = .28) for total fruits, and 0.94 (0.86 to 1.02, Ptrend = .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, Ptrend = .06). The age-standardized incidence rates of colon cancer for these two intake categories were 54 and 61 per 100000 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, Ptrend = .02) for distal colon cancers and 1.02 (0.82 to 1.27, Ptrend = .57) for proximal colon cancers. Similar site-specific associations were observed for total fruits and total vegetables.
Conclusion: 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.
| Context and Caveats Prior knowledge Fruit and vegetable intakes have been associated with a reduced risk of colon cancer; however, in more recent studies, associations have been less consistent. Study design Pooled analysis of 14 prospective studies. Contribution Increasing fruit and vegetable intakes were not associated with colon cancer risk overall, although the lowest intakes were associated with an elevation in risk. When examined by colon site, the inverse association for fruits and vegetables was limited to cancers of the distal colon, although the risk estimates for distal and proximal colon cancer were not statistically significantly different. Results for each fruit and vegetable group were generally consistent between men and women. Implications Diets plentiful in fruits and vegetables remain important given these findings and the benefits that have been observed for other health outcomes. Limitations The study was survey based, and there may have been inaccuracies in reported fruit and vegetable intake. Further, only data on diet at the beginning of each study were available for each study so it was not possible to evaluate associations between fruit and vegetable intakes during childhood, adolescence, or early adulthood and colon cancer risk.
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Manuscript received February 21, 2007; revised July 9, 2007; accepted August 7, 2007.
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J Natl Cancer Inst 2007 99: 1421.
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