Researchers at the Fred Hutchinson Cancer Research Center in Seattle, Wash., led by Emily White, Ph.D., a member of the public health sciences division, asked 35,016 postmenopausal women who did not have a history of breast cancer to complete a 24-page questionnaire about their use of non-vitamin, non-mineral "specialty" supplements in the Vitamins and Lifestyle (VITAL) cohort study.
After six years of follow-up, 880 cases of breast cancer were identified using the Surveillance, Epidemiology and End Results registry.
Regular use of fish oil supplements, which contain high levels of the omega-3 fatty acids, EPA and DHA, was linked with a 32 percent reduced risk of breast cancer. The reduction in risk appeared to be restricted to invasive ductal breast cancer, the most common type of the disease.
The use of other specialty supplements, many of which are commonly taken by women to treat symptoms of menopause, was not associated with breast cancer risk.
This research is the first to demonstrate a link between the use of fish oil supplements and a reduction in breast cancer. Studies of dietary intake of fish or omega-3 fatty acids have not been consistent.