Men with high concentrations of omega 3s also had a 71% higher risk of high-grade prostate cancer and a 44% higher risk of lowgrade prostate cancer. High-grade tumors are more likely to be fatal than low-grade tumors.
The reason for the association between high levels of omega-3s and prostate cancer is unknown. The study did not demonstrate that the fatty acids caused the cancer; it linked them to increased occurrences of prostate cancer. Two previous studies found a similar relationship.
The authors suggested that fatty acids could be involved in prostate tumor growth, and men should consider the potential risks of consuming more fatty acids, including taking fish oil supplements.
The difference in blood concentrations of omega-3s between the men with the highest and lowest levels was about 2.5%. This correlates to approximately two extra servings of salmon per week. The study looked specifically at blood levels of omega-3s, so the researchers did not know if the men with high levels of omega-3s took fish oil supplements or ate greater amounts fatty fish than men with low levels of the fatty acids. Other factors, such as genetics, could affect the increased risk of prostate cancer.
“Because of this study, I have recommended to my patients to discontinue taking fish oil supplements and eat a balanced diet, avoid excessive use of vitamins and supplements – everything in moderation.”–Dr. William J. Catalona
Brasky TM., et al. “Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial.” J Natl Cancer Inst. 2013; 105(15):1132-41.