In 2013, a paper from Brasky et al suggested a link between intake of marine omega 3 fatty acidsand the risk of developing prostate cancer. A new, comprehensive meta-analysis from Alexander et al which included studies using both self-reported dietary intake and biomarker studies did not support an association between marine omega 3 fatty acid intake and prostate cancer.
In the USA, prostate cancer is the most common form of cancer among men. The precise causes are unknown, but age, family history, Afro-Caribbean descent have been found to be associated with the disease. It is also believed that factors such as obesity, lack of exercise and smoking increase the risk, but the magnitude of increased risk has yet to be determined. A report by the World Cancer Research Fund (2) in 2007 reported that no dietary factors had yet been demonstrated as risk factors for the development of prostate cancer.
In 2013, Brasky et al. produced a paper that used a fixed effects meta-analysis model and examined prospective nested case-control and case-cohort studies that concluded there were some significantly positive associations with EPA & DHA intake and prostate cancer incidence. Contrary to other findings, trans-fat consumption was shown to be protective by this model. Use of a more comprehensive statistical model such as the random-effect model may have delivered a different result as it accounts for variation both between studies and within individual studies.
The Alexander et al 2015 meta-analysis included the data from the two aforementioned Brasky studies. In fact, it included 12 self-reported dietary intake and nine biomarker studies, which includes totals of 446,243 and 14,897 participants respectively. Even using the same statistical model as Brasky, there was no association between omega 3 fatty acid intake and risk of prostate cancer. Indeed the trends suggested a protective effect, but these did not achieve significance.
From a biological plausibility point of view, it would make sense that marine omega 3 fatty acids inhibit prostate carcinogenesis. It is known they have anti-inflammatory, pro-apoptotic and ant-proliferative effects on prostate cancer cells. Conversely, trans-fats have been shown to be strongly pro-inflammatory.