OBJECTIVE: To generate the evidence for an association between blood level omega-3 polyunsaturated fatty acid (n-3 PUFA) and prostate cancer risk through a meta-analysis of epidemiological studies.
METHODS: MEDLINE, Unbound MEDLINE, EMBASE, Science Direct, OVID, Proquest and Cochrane Library databases up to September2011 were searched. All studies included described effect estimates of high blood level omega-3 FA on prostate cancer risk in humans. Critical appraisal was done by two independent reviewers. Data were pooled using the general variance-based method with random-effects model; derived effect estimates were expressed as risk ratio (RR) with 95% confidence interval. Heterogeneity was assessed by Chi? and quantified by F, publication bias was also determined using Begg and Egger's test.
RESULTS: Twelve epidemiological studies were included (6 prospective and 6 retrospective case control studies). The overall effect esti mate of blood level n-3 PUFA in general has no association with total prostate cancer, advanced prostate cancer and high grade tumor risk. Significant negative association was noted between high blood level of n-3 PUFA docosapentaenoic acid (DPA) and total prostate cancer risk(RR:0.756; 95% CI 0.599, 0.955; P=0.019); this finding was generated from homogenous studies (P=0.566; P=O%) with no publication bias. Likewise, a positive association was noted between high blood level of fish oil content n-3 PUFA, eicosapentanoic acid and docosahexanoic acid, (EPA+DHA) and risk of high grade prostate tumor (RR: 1.381; 95%CI 1.050, 1.817; P=0.02l); however, this finding was evident only after adjustment was done on inter-study variability through removal ofa lower quality study from the pool.Notably, a non-significant positive association was also found between high blood levels of alpha-linolenic acid (ALA) and total prostate cancer risk (RR: 1.188 ;95%CI 0.955, 1.477; P=0.123), with no significant heterogeneity (P=0.24, P=22%) nor publication bias.
CONCLUSIONS: This review provided evidence showing high blood levels of n-3 PUFA DPA is associated with reduced total prostate cancer risk. While high blood level ofEPA+DHA is associated with increased high grade prostate tumor risk. These findings warrant further clinical studies to clarify associations.