A prospective study of trans-fatty acid levels in blood and risk of prostate cancer.

BACKGROUND: Previous studies suggest a positive association between markers of trans-fatty acid intake and prostate cancer. We therefore prospectively evaluated the association between blood trans-fatty acid levels and risk of prostate cancer. METHODS: We conducted a nested case-control study among 14,916 apparently healthy men who provided blood samples in 1982. Blood fatty acid levels were determined for 476 men diagnosed with prostate cancer during a 13-year follow-up and their matched controls. Controls were individually matched to cases according to age and smoking status at baseline. Conditional logistic regression was used to estimate the relative risk and 95% confidence interval of total, nonaggressive (stage A/B and low grade), and aggressive (stage C/D, high grade, subsequent distant metastasis or death) prostate cancer associated with blood levels of specific trans-fatty acids. RESULTS: Blood levels of all the trans-fatty acids examined were unrelated to total prostate cancer risk. When results were divided according to tumor aggressiveness, blood levels of 18:1n-9t, all the 18:2t examined, and total trans-fatty acids were positively associated to nonaggressive tumors. The relative risks (95% confidence intervals; P trend) comparing top with bottom quintile trans-fatty acid levels were 2.16 (1.12-4.17; 0.11) for 18:1n-9t, 1.97 (1.03-3.75; 0.01) for total 18:2t, and 2.21 (1.14-4.29; 0.06) for total trans-fatty acids. None of the trans fats examined was associated with aggressive prostate tumors. CONCLUSION: Blood levels of trans isomers of oleic and linoleic acids are associated with an increased risk of nonaggressive prostate tumors. As this type of tumors represents a large proportion of prostate cancer detected using prostate-specific antigen screening, these findings may have implications for the prevention of prostate cancer.