Abstract B131: A prospective study of phytanic acid intake from red meat and dairy products and prostate cancer risk

Abstract

Abstract B131 Phytanic acid - a 3-methyl branched-chain fatty acid - is found almost exclusively in red meat and dairy products, and may contribute to the increases in prostate cancer risk that are consistently observed with higher intakes of these animal foods. The potential importance of phytanic acid in prostate carcinogenesis is further underscored by evidence that the branched-chain fatty acid oxidation pathway is selectively upregulated in prostate tumors. We constructed a novel summary measure of phytanic acid intake and prospectively examined its association with prostate cancer risk in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study cohort. At baseline, 27,111 Finnish male smokers 50 to 69 years old provided information on demographic, smoking, medical, and other risk factors, and completed a 276-item diet history questionnaire that ascertained frequency of consumption and portion size. Since phytanic acid is not currently included in food composition tables, we used the published phytanic acid content of 151 major food items, including butter, cheese, cream, ice cream, milk, yogurt, and beef products, to estimate total daily intake. Between 1985 and 2006, a total of 1,929 incident prostate cancer cases, including 438 cases of advanced disease (defined as TNM stage 3 or 4 and / or Gleason grade of 8 or higher), were identified. In Cox proportional hazards models adjusted for age, smoking dose and duration, body mass index, education, family history of prostate cancer, energy intake, and trial intervention assignment, higher estimated phytanic acid intake was associated with increased risks of advanced prostate cancer in a non-linear manner. The relative risks and 95% confidence intervals for advanced prostate cancer according to increasing quartiles of phytanic acid intake were 1.00 (referent), 1.29 (0.90-1.86), 1.56 (1.11-2.21), and 1.34 (0.94-1.92); p trend = 0.23. Phytanic acid intake was unrelated to the risk of localized disease. Our study provides evidence for the first time that increased consumption of phytanic acid may be associated with higher risks of advanced prostate cancer, and provides a putative mechanistic explanation for previously observed associations between red meat and dairy product consumption and prostate cancer risk. Citation Information: Cancer Prev Res 2008;1(7 Suppl):B131.