[Proc Amer Assoc Cancer Res, Volume 47, 2006]
Epidemiology 10: Diet and Cancer Risk
A prospective study of blood trans fatty acid levels and risk of prostate cancer
Walter Willett and
Harvard School of Public Health, Boston, MA, Divisions of Aging and Preventive Medicine, Department of Medicine, Brigham and Womens Hospital and Harvard Medical School, Boston, MA, Channing Laboratory, Department of Medicine, Brigham and Womens Hospital and Harvard Medical School, Boston, MA
Purpose: Results from two previous studies suggest a positive association between markers of trans fatty acid (TFA) intake and prostate cancer. We therefore prospectively evaluated the association between blood TFA levels and risk of prostate cancer. Methods: We conducted a nested case-control study among 14,916 U.S. physicians who provided a blood sample in 1982. Blood samples were frozen at baseline and kept at 82° C until assayed. Incident prostate cancer cases accrued through 1995 were matched to controls by age, smoking status at baseline and length of follow-up. TFA levels as percentage of total fatty acids were determined for 479 cases and their 491 matched controls using gas chromatography. Cases and controls were divided into quintiles according to the distribution of TFA levels among the controls. Conditional logistic regression models were used to estimate the relative risk (RR) and 95% confidence interval (95% CI) of prostate cancer in a given quintile of TFA level in relation to the lowest quintile. Results: Levels of 16:1, 18:1 and total TFAs were not associated with prostate cancer risk. There was a weak positive association between levels of 18:2 TFAs, which result from the hydrogenation of linoleic acid, and prostate cancer risk. The RRs (95% CI) for men in successively higher quintiles of TFA levels were 0.87 (0.57 1.33), 1.24 (0.83 1.87), 1.69 (1.12 2.55) and 1.24 (0.81 1.88), compared to men in the lowest quintile (Ptrend = 0.09). The association was similar for the three 18:2 trans isomers examined: n-6 trans trans(tt), cis trans(ct) and trans cis(tc). When results were divided according to tumor stage at diagnosis, levels of 18:1, 18:2 and total TFAs were positively related to the risk of developing organ confined, but not advanced, tumors. The RRs (95% CI; Ptrend) of localized prostate cancer comparing the highest and lowest quintile of TFAs were 2.11 (1.22 3.64: 0.05) for total, 1.85 (1.08 3.16: 0.15) for 18:1, and 1.84 (1.05 3.22: 0.003) for 18:2 TFAs. Similar results were obtained for non-aggressive tumors (organ confined and Gleason 7). The RRs (95% CI; Ptrend) of non-aggressive prostate cancer comparing extreme quintiles of total, 18:1 and 18:2 TFA levels were 2.47 (1.32 4.63: 0.01), 2.10 (1.13 3.91: 0.06) and 2.29 (1.22 4.30: <0.001), respectively. None of the TFAs explored were associated with advanced (stage C or D) or aggressive tumors (stage C, D, or Gleason > 7). Further adjustment for potential confounders did not substantially change these results. Conclusions: Our prospective data suggests that blood levels of trans fatty acids, in particular trans fats resulting from the hydrogenation of vegetable oils, are associated with an increased prostate cancer risk. This association appears to be specific to organ confined and non-aggressive tumors.
Copyright © 2006 by the American Association for Cancer Research.