Participants were female members of the VITamins And Lifestyle (VITAL) Cohort. Postmenopausal women, ages 50 to 76 years, who were residents of western Washington state, completed a 24-page baseline questionnaire in 2000 to 2002 (n = 35,016). Participants were queried on their recency (current versus past), frequency (days/week) and duration (years) of specialty supplement use.

 

Incident invasive breast cancers (n = 880) from 2000 to 2007 were obtained from the Surveillance, Epidemiology, and End Results registry.

 

Current use of fish oil was associated with reduced risk of breast cancer. Ten-year average use was suggestive of reduced risk. These results held for ductal but not lobular cancers. Other specialty supplements sometimes taken for menopausal symptoms (black cohosh, dong quai, soy and St. John’s wort) were not associated with cancer risk.