Researchers in the Public Health Sciences Division found regular use of fish oil supplements, which contain high levels of the omega-3 fatty acids EPA and DHA, is associated with a 32 percent reduction in breast cancer risk. The findings—the first to demonstrate such a link—were published in the July issue of the journal Cancer Epidemiology, Biomarkers & Prevention.

The research, led by Dr. Emily White and funded by the National Cancer Institute, adds to the growing evidence that fish oil supplements may play a role in preventing chronic disease.

The study asked 35,016 postmenopausal women who did not have a history of breast cancer to complete a 24-page questionnaire about their use of nonvitamin, nonmineral “specialty” supplements.

After six years of follow-up, 880 cases of breast cancer were identified using the Surveillance, Epidemiology and End Results registry. 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.

Studies of dietary intake of fish or omega-3 fatty acids have not been consistent.

“It may be that the amount of omega-3 fatty acids in fish oil supplements are higher than most people would typically get from their diet,” said White, who is also a professor and associate dean of the University of Washington’s School of Public Health.

White cautioned against gleaning any recommendations from the results of one study.

“Without confirming studies specifically addressing this, we should not draw any conclusions about a causal relationship,” she said.

Co-authors include Drs. Theodore Brasky, Johanna Lampe and John Potter, all of PHS, and former Center researcher Dr. Ruth Patterson, now at University of California, San Diego.