OBJECTIVE: To determine the relationship between dietary omega-3 fatty acid(n-3PUFA) and omega-6 fatty acids (n-6PUFA) with prostate cancer risk from a meta-analysis of prospective cohort studies.

DESIGN: Cohort studies that investigated the relationship of dietary omega fatty acids and prostate cancer risk were retrieved from MEDLINE, Unbound MEDLINE, EMBASE, OVID, Cochrane Library and Science direct up to June 2011, and were critically appraised using Newcastle-Ottawa Quality Assessment for cohorts. General variance-based method was used to the pool the effect estimates at 95% confidence interval. Heterogeneity was assessed by chi square and quantified by I2.

RESULTS: Eight cohort studies were included for meta-analysis. n-3PUFA, n-6PUFA and their derivatives were not significantly associated with risk of prostate cancer in general. A significant heterogeneity (P=0.023,I2=63%) between studies was noted. After inter-study variability adjustment was done, repeat analysis showed a significant negative association between high dietary intake of alpha-linolenic acid(ALA) and prostate cancer risk (pooled RR:0.915;95% CL:0.849, 0.985;P=0.019) Likewise, a slightly positive association was noted on dietary long chain omega-3 fatty acids (EPA+DHA) and prostate cancer risk (pooled RR: 1.135; 95% CI:1.008, 1.278 P=0.036), however when two other cohort studies with data of EPA and DHA both analyzed separately was included into the pool, the association became not significant (RR=1.034;95%CI:0.973,1.096;P=0.2780).

CONCLUSION: The intake of n-3PUFA and n-6PUFA does not significantly affect the risk of prostate cancer. High intake of ALA may reduce risk of prostate cancer, while intake of long-chain omega-3 fatty acids does not have a significant effect.