Omega 3's may increase prostate cancer risk
A recently published study in the Journal of the National Cancer Institute looks deeper into data from the Selenium and Vitamin E Cancer Prevention Trial (SELECT). Past reported results of this trial showed no evidence of a protective effect of the supplements, and in 2011, after additional follow-up, it was found that participants that took vitamin E alone had a 17 percent increased risk of prostate cancer compared to men on the placebo supplement. More information about the SELECT trial is available from NCI: www.cancer.gov/newscenter/qa/2008/selectqa
Theodore M. Brasky, Ph.D., Research Assistant Professor at The Ohio State University Comprehensive Cancer Center, and his colleagues recently looked back at data and plasma collected in the SELECT trial with the aim of investigating the effect of consumption of ω-3 fatty acids (omega 3 fatty acids). In previous reported work* using data and serum collected from the Prostate Cancer Prevention Trial, Brasky and colleagues reported that a high concentrations of serum phospholipid long chain omega 3 fatty acids was associated with a large increase in the risk of high-grade prostate cancer, and high concentrations of trans-fatty acids were associated with reduced risk of high-grade prostate cancer. These findings are counter to some expectation about the omega 3 fatty acids and authors wished to learn more about inconsistencies in previous research showing that increased omega 3 consumption could lead to decreased cancer risk.
The current study, funded by the National Cancer Institute and the National Center for Complementary and Alternative Medicine**, used a case-cohort design of subjects within the SELECT trial. Case subjects included 834 men diagnosed with prostate cancer. The subcohort consisted of 1,393 men without cancer who were selected randomly and matched to case subjects on age and race. Phospholipid fatty acid assays were performed on blood serum of case and subcohort subjects.
Authors found that, "The mean percentages of total long-chain ω-3 polyunsaturated fatty acids [PUFA] were statistically significantly higher in total, low-, and high-grade prostate cancer case subjects compared with the subcohort." Specifically, "compared with men in the lowest quartile of total long chain omega 3 PUFA, men in the highest quartile had a 44%, 71% and 43% increased risks for low-grade, high-grade, and total cancer, respectively."
In conclusion, authors found that long chain omega 3 PUFA overall, and docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) in particular, were associated with strong linear, increases in prostate cancer risk. Since this data was similar to findings of two other studies, authors note that the replication strongly suggests that long chain omega 3 PUFA do play a role in enhancing prostate tumorgenesis. These finding should be taken into consideration with other studies related to fatty acid intake and cancer risk before starting a regime of increased fatty acid supplement intake.
For more information on this study, view the report online: http://www.ncbi.nlm.nih.gov/pubmed/23843441
*Brasky, T.M., Till, C., White, E., Neuhouser, M.L., Song, X., Goodman, P., … Kristal, A.R.(2011). Serum phospholipid fatty acids and prostate cancer risk: results from the prostate cancer prevention trial. American Journal of Epidemiology, 173(12),1429-39. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/21518693