Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Epidemiology and Biostatistics

Supervisor

Karp, Igor

2nd Supervisor

Choi, Yun-Hee

Abstract

Colorectal cancer (CRC) is the third most common type of cancer in Canada. Some dietary factors have been identified for the prevention of CRC; however, the effect of consuming fish, fruit, non-starchy vegetables, coffee, or tea remains unclear. The associations between these dietary variables and CRC were investigated using 346 cases and 309 controls from the COLDENT case-control study. To incorporate duration and intensity of consumption, a measure of serving-years/cup-years was used. Multivariable logistic regression was used and included many covariates for adjustment. Associations of cumulative fish, fruit, non-starchy vegetable, coffee, and tea consumption with CRC were almost null. Results for recent past, distant past, and very distant past consumption categories were also close to null. Considering the potential for bias, the results suggest that the true association between these dietary exposures and CRC is not very strong.

Summary for Lay Audience

Colorectal cancer (CRC) is one of the most common types of cancer, globally and in Canada. CRC that is not related to a genetic predisposition to CRC is referred to as sporadic. In an effort to prevent the occurrence of sporadic CRC, a number of dietary risk factors have been identified, including alcohol consumption and red meat consumption. However, it is not yet clear if the consumption of fish, fruit, non-starchy vegetables, coffee, and tea has an effect on the occurrence of CRC. Based on previous literature, it was expected that consumption of these dietary items would prevent CRC.

The effect of fish, fruit, non-starchy vegetables, coffee, and tea on CRC was investigated using the COLDENT study. This study consisted of 655 men and women age 40 to 80 years. There were 346 people with a diagnosis with CRC. Everyone in the study was asked to provide information on their diet from age 20 to the present. Information on other CRC risk factors was also collected. Consumption of the dietary variables was measured as cumulative consumption starting from age 20. Since CRC takes many years to form, consumption of dietary factors was also categorized based on the recent past, distant past, and very distant past. The association between these dietary variables was adjusted for using established CRC risk factors.

The results of this study found that cumulative consumption of fish, fruit, non-starchy vegetables, coffee, and tea did not have an effect on the CRC. There was also no effect on CRC when considering the recent past, distant past, and very distant past consumption of these dietary factors. Taking in consideration inaccuracies that results from a person’s ability to recall their past diet, the results indicate that if an effect for these dietary factors truly exist, the effect on CRC is not strong. Future studies should continue focus on the timing of the dietary exposure when considering the effect of fish, fruit, non-starchy vegetables, coffee, and tea on CRC.

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