Fish oil consumption has been shown to be associated with reduced risk of breast cancer. This study uncovered the molecular mechanism of action of by which fish oil reduces breast cancer cell growth. Nude mice implanted with breast cancer tumors were fed a fish oil diet, which reduced the tumor burden. The diet was found to significantly increase the activity of PTEN, a tumor suppressor gene. Increased PTEN expression inhibits cancer cell growth promoting signals and enhances cell death signals. Further experimentation demonstrated that the marine omega-3 fatty acids found in fish oil were responsible for these effects.

Other studies have also found that fatty fish reduce breast cancer risk

Most, but not all, population studies have found an inverse association between consumption of fatty fish and risk of breast cancer. Marine fatty acids have also been found to enhance the therapeutic effects of taxane chemotherapy (e.g., Taxol). Healthy sources of marine omega-3 fatty acids include salmon, mackerel, and sardines.