M.Sc Thesis

M.Sc StudentChaiter Yoram
SubjectNutritional Epidemiology of Colorectal Cancer-Carotenoids
DepartmentDepartment of Medicine
Supervisor PROF. Gad Rennert


Background: Controversy exists around possible protective role of  carotenoids in the causation of colorectal cancer(CRC). No information exists about the role of their isomers.

Objectives : To examine the associations of  dietary intake  of  carotenoid isomers with the risk of developing CRC.

Methods: A  population based case- control study in Northern Israel with matched population controls. A semi quantitative food  frequency questionnaire was used. Carotenoid  isomers database was created by analyzing all  food items for carotenoid isomers content using HPLC.
 Mean daily intake  of carotenoid isomers was calculated.  Odds ratios and 95% confidence intervals were calculated from a conditional logistic regression model including energy, fiber, fat , vitamins D, C, E, fruits and vegetable consumption, age ,use of NSAID’S ,family history of CRC and physical activity as covariates.

Results : 712 pairs of cases and controls were included in analysis.9-cis- beta-carotene, all-trans beta-carotene, beta- zea-carotene, cis- beta-cryptoxanthin, zeaxanthin and lutein were inversely associated with CRC risk . In females, only 9-cis beta-carotene, all-trans beta-carotene and beta -zea-carotene were protective.  In the older age group (>70 yrs) ,only 9- cis beta carotene, all -trans- beta carotene and beta- zea- carotene were found protective.
No protective effects of carotenoids were noticed in  current smokers.
In Ashkenazi Jews 9-cis beta-carotene, all-trans- beta-carotene and beta- zea-carotene were found protective. Only all-trans- beta-carotene was found to be protective in Sephardi Jews 9-cis -beta-carotene, all-trans- beta-carotene, zeaxanthin and lutein  were protective against left side tumors of the colon. 9-cis beta-carotene and beta- zea-carotene were  protective against right side tumors. Rectal tumors were protected  by 9-cis- beta-carotene, zeaxanthin and lutein .
Lycopene increased the risk of CRC in  most subgroups except in Sephardic Jews and current smokers.

The protective effects of carotenoid isomers differed by age, ethnicity and gender. A broader protective effect was noticed for left-sided colon tumors.The finding of lycopene as increasing the risk of CRC is intriguing and deserves  further study.