High levels of omega-3 in the blood -- which is good for the heart -- may boost the risk of aggressive prostate cancer in men, U.S. researchers found. Theodore M. Brasky and colleagues at the Fred Hutchinson Cancer Research Center in Seattle analyzed data from a nationwide study involving more than 3,400 men. Half developed prostate cancer during the course of the study and half did not. The study, published in the American Journal of Epidemiology, found men with the highest blood percentages of docosahexaenoic acid, or DHA -- an inflammation-lowering omega-3 fatty acid commonly found in fatty fish such as salmon -- have two-and-a-half-times the risk of developing aggressive, high-grade prostate cancer compared to men with the lowest DHA levels. In addition, the study found men with the highest blood ratios of trans-fatty acids -- linked to inflammation and heart disease and abundant in processed foods that contain partially hydrogenated vegetable oil -- had a 50 percent reduction in the risk of high-grade prostate cancer. Neither fat was associated with the risk of low-grade prostate cancer risk. \"We were stunned to see these results and we spent a lot of time making sure the analyses were correct,\" Brasky said in a statement. \"Our findings turn what we know -- or rather what we think we know -- about diet, inflammation and the development of prostate cancer on its head.\" However, overall, the beneficial effects of eating fish to prevent heart disease outweigh any harm related to prostate cancer risk, Brasky adds.