Are Blood Levels of Omega-3 Fatty Acids Related to an Increased Risk of Developing Prostate Cancer?

Prostate cancer is the second leading cause of cancer death in U.S. men, with annual mortality of approximately 32,000. Nearly 175,000 new cases of prostate cancer are diagnosed in the U.S. per year.

Inflammation plays a role in many types of cancer, including prostate cancer. A number of variables such as obesity and diet have been shown to be related to inflammation. For example, long-chain polyunsaturated omega-3 fatty acids have anti-inflammatory effects. These fatty acids, otherwise known as fish oils, are found mostly in fatty fish and dietary supplements and have also been shown to be beneficial for cardiovascular health. While most studies have not shown an association between fish oils and prostate cancer, there was one large study published in 2013 that did show an increased risk of prostate cancer, particularly more aggressive cancer, with increased blood levels of omega-3 fatty acids. Thus, the goal of the current study was to examine the relationship between baseline levels of omega-3 fatty acids and prostate cancer development in a sample of healthy men. A secondary goal of this study was to add our findings to an existing meta-analysis of similar studies.

We used a sample of 5607 healthy men with no history of prostate cancer. All men underwent at least two comprehensive medical examinations at the Cooper Clinic in Dallas, Texas between 2007 and 2019. At the baseline exam, blood levels of omega-3 fatty acids were measured by using a method called the Omega-3 Index (O3I). The O3I measures the percentage of fatty acids in red blood cell membranes that are composed of omega-3’s. A value of <4% is considered low, while values of 4-8% and >8% are considered normal and high, respectively. The men were then followed for an average of 5.1 years between exams, during which time 116 new cases of prostate cancer were identified.

Our main findings were as follows:

• Using the Low O3I category as a reference group, men in the Normal and High categories were 22% and 28% less likely to develop prostate cancer, respectively. We note that these differences were not statistically significant, but trended in the right direction.
• For each 1% increment in the O3I, men were 4% less likely to develop prostate cancer. Again, while this was not statistically significant, it trended in the right direction.
• When added to 9 previous studies on the same topic, the overall conclusion was that there is no significant relationship between the O3I and future risk of prostate cancer.

Conclusion    

Because of the overwhelming majority of studies including the current one, men can continue to consume 1-2 fatty fish meals per week as advised by the American Heart Association and/or take omega-3 supplements in order to benefit their cardiovascular health without being concerned that doing so will increase their risk of future prostate cancer. Men over 40 years of age are encouraged to see their urologist annually for a prostate health exam, particularly if there is a family history of prostate cancer.      

References

1. Brasky, T.M.; Darke, A.K.; Song, X.; Tangen, C.M.; Goodman, P.J.; Thompson, I.M.; Meyskens, F.L., Jr.; Goodman, G.E.; Minasian, L.M.; et al. Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. J. Natl. Cancer Inst. 2013. 105:1132–1141. doi:10.1093/jnci/djt174.
2. Farrell, S.W., DeFina, L.F., Tintle, N.L., Leonard, D., Cooper, K.H., Barlow, C.E. Haskell, W.L., Pavlovic, A., Harris, W.S. Association of the Omega-3 Index with Incident Prostate Cancer with Updated Meta-Analysis: The Cooper Center Longitudinal Study. Nutrients. 2021. 13:384. https://doi.org/10.3390/nu13020384