A startling study shows men who have the highest levels of these compounds—the kinds found in fish but not in vegetable sources—have a higher risk of prostate cancer. Men with the very highest levels had a 71 percent higher risk of high-grade prostate cancer—the kind most likely to spread and kill, they report in the Journal of the National Cancer Institute.Fatty acids found in vegetable oils, flaxseeds and other vegetable sources—including alpha-linolenic acid (ALA)–did not affect prostate cancer risk, the researchers found.Brasky, who says he still eats fish "but in moderation", says the study cannot answer the question of how fish oil might cause cancer. They took into account other factors that might be associated with eating fish and Brasky notes that mercury, which can be found in fatty fish, doesn't cause prostate cancer.The study also doesn't say anything about the effects of fish oil on men who already have cancer. "This study is not about men with prostate cancer," Brasky said, noting that some studies have suggested fish oil might be beneficial in men who already have cancer.

Men might be at a loss for what to do, as omega-3 fatty acids were also believed to lower the risk of heart disease, which is far more common than prostate cancer. The American Heart Association recommends that people with heart disease eat fish twice a week and people with heart disease might need fish oil capsules.

But the researchers point out that recent studies have shown taking extra omega-3 has little effect on heart disease–including a study published in the New England Journal of Medicine in May.
(Google "CNBC fish oil study" for the full article as the above is a compendium). As far as I can make out women, as they say, are off the hook.