Coffee, tea, and caffeine consumption and incidence of colon and rectal cancer.
BACKGROUND
Frequent coffee consumption has been associated with a reduced risk of colorectal cancer in a number of case-control studies. Cohort studies have not revealed such an association but were limited in size. We explored the association between consumption of coffee and tea and the incidence of colorectal cancer in two large prospective cohorts of women and men.


METHODS
We used data from the Nurses' Health Study (women) and the Health Professionals' Follow-up Study (men). Consumption of coffee and tea and total caffeine intake were assessed and updated in 1980, 1984, 1986, 1990, and 1994 among women and in 1986, 1990, and 1994 among men. The incidence of cancer of the colon or rectum was ascertained through 1998. Hazard ratios were calculated using Cox proportional hazards models that adjusted for potential confounders. All tests of statistical significance were two-sided.


RESULTS
During almost 2 million person-years of follow-up, 1438 cases of colorectal cancer were observed. Consumption of caffeinated coffee or tea with caffeine or caffeine intake was not associated with the incidence of colon or rectal cancer in either cohort. For both cohorts combined, the covariate-adjusted hazard ratio for colorectal cancer associated with consumption of each additional cup of caffeinated coffee was 0.99 (95% confidence interval [CI] = 0.96 to 1.03). However, participants who regularly consumed two or more cups of decaffeinated coffee per day had a 52% (95% CI = 19% to 71%) lower incidence of rectal cancer than those who never consumed decaffeinated coffee.


CONCLUSIONS
Consumption of caffeinated coffee, tea with caffeine, or caffeine was not associated with incidence of colon of rectal cancer, whereas regular consumption of decaffeinated coffee was associated with a reduced incidence of rectal cancer.
Michels
Karin B
KB
Obstetrics and Gynecology Epidemiology Center, Brigham and Women's Hospital, and Harvard Medical School, 221 Longwood Ave., Boston, MA 02115, USA. kmichels@rics.bwh.harvard.edu
Willett
Walter C
WC
Fuchs
Charles S
CS
Giovannucci
Edward
E
D000328:Adult; D000368:Aged; D002110:Caffeine / Q000008:administration & dosage*; D003069:Coffee; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control*; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D016016:Proportional Hazards Models; D011446:Prospective Studies; D015203:Reproducibility of Results; D018570:Risk Assessment; D011795:Surveys and Questionnaires; D013662:Tea
D003069:Coffee; D013662:Tea; D002110:Caffeine