The regular consumption of fish-oil has a potentially favourable role in inflammation, carcinogenesis inhibition and cancer outcomes. An analysis of the literature aimed to review the evidence for the roles of dietary-fish and fish-oil intake in prostate-cancer (PC) risk, aggressiveness and mortality.
A systematic-review, 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.
A total of 37-studies with 495,321 participants were analysed. They 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.
The authors concluded that 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.
Several other recent reviews have also generated encouraging evidence, e.g.:
…omega-3 fatty acids may exert their anticancer actions by influencing multiple targets implicated in various stages of cancer development, including cell proliferation, cell survival, angiogenesis, inflammation, metastasis and epigenetic abnormalities that are crucial to the onset and progression of cancer.
If I was aiming for a career as a cancer quack, I would now use this evidence to promote my very own cancer prevention and treatment diet. As I have no such ambitions, I should tell you that regular fish oil consumption is no way to treat cancer. It also is no way to prevent cancer. If anything, it might turn out to be a way of slightly reducing the risk of certain cancers. To be sure, we need a lot more research, and once we have it, fish oil will be entirely mainstream. Raising false hopes regarding ‘alternative cancer cures’ based on fairly preliminary evidence is counter-productive, unethical and irresponsible.