Men Who Consume Vegetable Oils Rich in Monounsaturated Fat: Their Dietary Patterns and Risk of Prostate Cancer (New Zealand)

Objectives: To investigate (i) dietary patterns associated with consumption of vegetable oils rich in monounsaturated fatty acids (MUFA), and (ii) the risk of prostate cancer associated with consumption of these oils. Methods: A population-based case-control study was conducted in Auckland, New Zealand, involving 317 prostate cancer cases and 480 controls. A food-frequency questionnaire was used to collect data concerning consumption of MUFA-rich vegetable oils (including olive oil, canola or peanut oil) and other dietary variables. Biomarkers for fatty acids were measured in erythrocytes. Results: The group of participants who reported regular consumption of greater than 5.5 ml of MUFA-rich vegetable oils per day had a diet relatively high in monounsaturated fat, vegetables, lycopene, vitamin E, selenium, and n-3 fish oils. Increasing levels of MUFA-rich vegetable oil intake were associated with a progressive reduction in prostate cancer risk (multivariate relative risk = 0.5; 95% confidence interval 0.3-0.9; > 5.5 ml per day vs. non-consumption, p trend = 0.005), and similar trends were observed across all strata of socioeconomic status. Prostate cancer risk was not associated with intake of total MUFA or the major animal food sources of MUFA. Conclusion: This finding may be explained by the protective effect of an associated dietary pattern high in antioxidants and fish oils, an independent protective effect of MUFA-rich vegetable oils unrelated to the MUFA component, or a combination of these factors.