Garlic consumption and colorectal cancer risk in the CPS-II Nutrition Cohort.
OBJECTIVE
The World Cancer Research Fund/American Institute for Cancer Research identified a probable role for garlic in colorectal cancer prevention based on preclinical evidence and epidemiologic studies, but prospective data are limited. The purpose of this paper was to contribute additional evidence on this topic for men and women in a large prospective cohort study.


METHODS
In 1999, 42,824 men and 56,876 women in the Cancer Prevention Study II Nutrition Cohort completed a questionnaire with information on dietary garlic consumption. Garlic supplement use was assessed in 2001. Cox proportional hazards regression was used to estimate multivariable-adjusted hazard rate ratios (HRs) and 95 % confidence intervals (CIs).


RESULTS
During 7 years of follow-up, 579 men and 551 women were diagnosed with colorectal cancer. Among men, daily garlic consumption was associated with a non-significant higher colorectal cancer risk (HR = 1.04, 95 % CI 0.99-1.08 for each additional clove or "4 shakes" of garlic per week), whereas the association was borderline inverse in women (HR = 0.95, 95 % CI 0.91-1.00, p heterogeneity by sex = 0.03). Garlic supplement use was not related to a lower risk of colorectal cancer, and in men, former use was associated with a higher risk of colorectal cancer (HR = 1.85, 95 % CI 1.13-3.03).


CONCLUSIONS
These results provide weak support for a role of dietary garlic consumption in colorectal cancer prevention in women, but a possible increased risk in men. Further research is needed to confirm different associations by sex.
Epidemiology Research Program, American Cancer Society, Atlanta, GA 30303-1002, USA. marji.mccullough@cancer.org
Marjorie L
ML
McCullough
Eric J
EJ
Jacobs
Roma
R
Shah
Peter T
PT
Campbell
Susan M
SM
Gapstur
D000368:Aged; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000209:etiology* / Q000517:prevention & control*; D019587:Dietary Supplements; D005260:Female; D005500:Follow-Up Studies; D005737:Garlic; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012044:Regression Analysis; D012306:Risk