The study focused on the potential health benefits of 15 different supplements on breast cancer risk. The Fred Hutchinson Cancer Research Center in Seattle says the only one that had any effect was fish oil.
Fish oil supplements made from fatty fish such as salmon contain high levels of Omega-3 fatty acids.
In the study, 35,000 Washington state women between the ages of 50 and 76 and all past menopause were asked questions about their use of non-vitamin, non-mineral supplements. None of the women had a history of breast cancer.
In a follow-up six years later, 880 women had been diagnosed with breast cancer. Researchers found the women who took fish oil on a regular basis had a 32 percent lower incidence of developing the illness.
The study is published in the July issue of Cancer Epidemiology, Biomarkers & Prevention.
The study's senior author said this is the first study to suggest a connection between fish oil supplements and reduced breast cancer risk. Earlier research has suggested that the Omega-3 fatty acids found in fish may be heart-healthy.
The American Cancer Society said more study is needed. Harvard researchers are enrolling participants to look at the impact of Omega-3 fatty acids and vitamin D on the risk of cancer, heart disease and stroke.