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Advisory Committee Chair

John W Waterbor

Advisory Committee Members

Emily B Levitan

Xiao-Ou Shu

Yong-Bing Xiang

Bin Zhang

Document Type

Dissertation

Date of Award

2013

Degree Name by School

Doctor of Philosophy (PhD) School of Public Health

Abstract

Colorectal cancer (CRC) is a major global health concern and the intake of certain foods, such as cruciferous vegetables, has been studied for their potential protective effects against cancer development. The observed association between cruciferous vegetable consumption and CRC has been inconsistent, possibly related to glutathione S-transferase (GST) gene polymorphisms. Therefore, we aimed to (1) evaluate the association between fruits and vegetables, including cruciferous vegetables, on the risk of CRC; (2) determine factors associated with urinary isothiocyanate (ITC), a biomarker of cruciferous vegetable intake; and (3) evaluate the association between cruciferous vegetable consumption and CRC and to estimate the potential interaction between cruciferous vegetable intake and GST gene polymorphisms using data from the Shanghai Men's Health Study (SMHS). In the SMHS cohort, 398 cases of CRC (236 colon and 162 rectum) were observed as of December 31, 2010. Fruit consumption was inversely associated with the risk of CRC while vegetable intake was not significantly associated with risk. Similarly, cruciferous vegetable intake was not significantly associated with colorectal, colon, or rectal cancer risk. Using data from nested case-control studies within the Shanghai Men's and Women's Health Studies, usual cruciferous vegetable intake as assessed by a food frequency questionnaire was weakly correlated with urinary ITC level, while recent cruciferous vegetable intake was more strongly correlated with urinary ITC. Overall, the GST genotypes were not associated with urinary ITC level, but significant differences according to genotype were observed among current smokers and participants who provided an afternoon urine sample. In the nested case-control study from the SMHS, CRC risk was not associated with cruciferous vegetable intake, whether measured by self-report or by urinary ITC, nor with GST gene variants. No statistical interactions were detected between cruciferous vegetable intake and GST gene variants on the odds of CRC. Stratifying by timing of urine sample collection (morning versus afternoon) and excluding colorectal cancer cases diagnosed in the first two years of follow-up did not materially alter the results. In conclusion, this study does not support an association between cruciferous vegetable intake and CRC in a population of middle-aged and older men in Shanghai, China.

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