Systematic review of prostate cancer risk and association with consumption of fish and fish-oils: analysis of 495,321 participants

Abstract

Introduction: Fish-oils have a potential role in inflammation, carcinogenesis inhibition and favourable cancer outcomes. There has been increasing interest in the relationship of diet with cancer incidence and mortality, especially for eicosapantaenoic acid (EPA) and docosahexaenoic acid (DHA). This systematic-analysis of the literature aims to review evidence for the roles of dietary-fish and fish-oil intake in prostate-cancer (PC) risk, aggressiveness and mortality. Methods: A systematicreview, following PRISMA guidelines was conducted. PubMed, MEDLINE and Embase were searched to explore PC-risk, aggressiveness and mortality associated with dietary-fish and fish-oil intake. 37 studies were selected. Results: A total of 495,321 (37-studies) participants were investigated. These revealed various relationships regarding PC-risk (n = 31), aggressiveness (n = 8) and mortality (n = 3). Overall, 10 studies considering PC-risk found significant inverse trends with fish and fish-oil intake. One found a dose-response relationship whereas greater intake of long-chain-polyunsaturated fatty acids increased risk of PC when considering crude odds-ratios [OR: 1.36 (95% CI: 0.99-1.86); p = 0.014]. Three studies addressing aggressiveness identified significant positive relationships with reduced risk of aggressive cancer when considering the greatest intake of total fish [OR 0.56 (95% CI 0.37-0.86)], dark fish and shellfish-meat (p < 0.0001), EPA (p = 0.03) and DHA (p = 0.04). Three studies investigating fish consumption and PC-mortality identified a significantly reduced risk. Multivariate-OR (95% CI) were 0.9 (0.6-1.7), 0.12 (0.05-0.32) and 0.52 (0.30-0.91) at highest fish intakes. Conclusions: Fish and fish-oil do not show consistent roles in reducing PC incidence, aggressiveness and mortality. Results suggest that the specific fish type and the fish-oil ratio must be considered. Findings suggest the need for large intervention randomised placebo-controlled trials. Review criteriaRecent studies have indicated that fish oil may be associated with an increased risk of prostate cancer, though other studies have presented conflicting results. Studies have included fish and fish oils to examine this relationship. Message for the clinicGreat inconsistence in study design limits metaanalysis. When considering fish consumption there is no direct link with prostate cancer incidence but relationships with reduced mortality have been demonstrated. Different fish oils present differing results regarding reductions in prostate cancer risk, aggression and mortality, thus more extensive research is required before consideration in nutritional therapy and cancer prevention. IntroductionThe role of fish-oils in preventing and treating disease has been investigated for over 50 years (1). Fish-oil is known to be a common source of omega-3 fatty acids and evidence suggests favourable outcomes relative to cancer symptoms such as fatigue and cachexia (2,3). Long-chain omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) form important componen...

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