Emily White linked a 32 percent reduced risk of breast cancer to regular use of fish oil supplements with high levels of the omega-3 fatty acids, EPA and DHA.

However, the study -- reported in Cancer Epidemiology, Biomarkers & Prevention -- finds reduced cancer risk was restricted to only the most common breast cancer type: invasive ductal breast cancer.

White notes supplements may be higher in omega 3-fatty acids than most people would typically get from their diet and cautions against gleaning recommendations from one study.

"We should not draw any conclusions about a causal relationship," White said in a statement.

White and colleagues had 35,016 post-menopausal women with no history of breast cancer complete a questionnaire about their use of non-vitamin, non-mineral "specialty" supplements. During six years of follow-up, 880 cases of breast cancer were identified.

White notes using other specialty supplements -- many commonly taken to treat symptoms of menopause -- did not seem to be associated with breast cancer risk.