Omega-3 fatty acids, taken by millions of people as a health supplement, could trigger aggressive prostate cancer, a study claims.
Research has shown the substance could increase the risk of high-grade disease by 71%.
Taking omega-3 was also associated with a 44% greater chance of developing low-grade prostate cancer. Overall, the fatty acids raised the risk of all prostate cancers by 43%.
Writing in the online edition of the Journal of the National Cancer Institute scientists said people considering increasing their intake of omega-3 "should consider its potential risks".