text: Prostate cancer The effect of fish oil consumption on prostate cancer is controversial. For instance, one study showed decreased risk with higher blood levels of DPA. However, another reported increased risk of more aggressive prostate cancer with higher blood levels of combined EPA and DHA. Some evidence indicated an association between high blood levels of omega-3 fatty acids and an increased prostate cancer risk.
  However, this evidence from the Select Trial has been challenged on the grounds of methodology and that the quantitative difference between those who developed prostate cancer and those who did not "is so small as to be biologically irrelevant".
  Cardiovascular
  There is uncertainty about the role of fish oil in cardiovascular disease, with reviews reaching different conclusions about its potential impact. Multiple evaluations suggest fish oil has little or no reduction on cardiovascular mortality, although there may be a small reduction in the incidence of actual cardiac events and strokes with its use. In 2007, the American Heart Association recommended the consumption of 1 gram of fish oil daily, preferably by eating fish, for patients with coronary artery disease, but cautioned pregnant and nursing women to avoid eating fish with high potential for mercury contaminants including mackerel, shark, and swordfish. (Optimal dosage was related to body weight.)