DOI: 10.25549/usctheses-c127-671963
title: Cooking oil, dietary fat, fat metabolizing genes, and prostate cancer risk in a multiethnic population

description: Dietary fat has been implicated as a potential promotional factor leading to progression of small, latent, non-metastatic prostate tumors to invasive, metastatic lesions.  One possible mechanism is conversion of the inflammatory compounds of the polyunsaturated fatty acids (PUFA) produced by the lipoxygenase (LOX) family of enzymes. PUFAs are found in many cooking oils, such as soybean, safflower, and sunflower. Furthermore, foods such as avocado, nuts, cereals, and poultry are rich in polyunsaturated fatty acids. The effect of cooking oil has not been extensively investigated, however, there is evidence of a relationship between dietary patterns and prostate cancer (Stacewicz-Sapuntzakis, 2008). We had three objectives: to examine the effects of dietary fat intake, type of cooking oil used, and whether genetic variants in the PUFA LOX pathways are associated with the risk of prostate cancer. We conducted a population-based case control study of advanced prostate cancer among African-Americans and Caucasians in Los Angeles County.  Dietary fat intake and preferred cooking oil were assessed by a food frequency questionnaire. To assess genetic variants, five LOX gene polymorphisms were examined: 12-LOX Gln261Arg (rs434473), and Ser322Asn (rs1126667), 15-LOX-2 Gln656Arg (rs4792147), 5-LOX Lys254Glu (rs4073259), and the 5-LOX promoter Sp1 motif polymorphism. ❧ We observed a statistically significant association between preferred cooking oil and risk of prostate cancer at all stages. Men, regardless of race, who used vegetable or corn oil, but not hydrogenated fat, were 1.83 times as likely to experience prostate cancer than men who used olive or canola oil; those who used hydrogenated oils were 1.57 times as likely to experience prostate cancer. Similar results were observed among men with localized or advanced stage prostate cancer. ❧ When we evaluated the risks isolated to a particular stage of prostate cancer, we observed that men who use vegetable or corn oil, but not hydrogenated fat, were 1.72 times as likely to experience localized prostate cancer than men who used olive or canola oil, and those who used hydrogenated oils were 1.59 times as likely to experience localized prostate cancer. Furthermore, we observe that men who used vegetable or corn oil, but not hydrogenated fat, were 1.87 times as likely to experience advanced stage prostate cancer than men who used olive or canola oil, and those who used hydrogenated oils were 1.50 times as likely to experience advanced stage prostate cancer. ❧ Among Caucasians, men who used vegetable or corn oil, but not hydrogenated fat, were 2.08 times as likely to experience prostate cancer than men who used olive or canola oil, and those who used hydrogenated oils were 1.53 times as likely. Among African-Americans, there was an increased risk, but it was not as significant as among Caucasians. ❧ We did not observe a statistically significant relationship between PUFA and risk when not taking genotype into account. A statistically significant interaction was observed between 12-LOX Gln261Arg and PUFA (p=0.04).  Among African-American men with the GG genotype, there was a decrease in risk of prostate cancer with PUFA intake below the median PUFA consumption.  Caucasian men with the AA genotype displayed an increase in risk with diets high in PUFAs.  Furthermore, we saw a statistically significant interaction between 12-LOX Ser322Asn and PUFA (p=0.02).  Among African-American men with diets low in PUFAs, there was a decrease in risk.