Fish oil linked to lower breast cancer risk

SEATTLE – Cancer Digest – The evidence that fish oil may prevent chronic diseases was given a boost this week with the first study showing that women who took the supplement had a 32 percent lower risk of breast cancer compared to similar women who didn’t.

But don’t go out and start taking omega-3 fatty acid supplements just yet, say the study's authors at Fred Hutchinson Cancer Research Center. Led by Dr. Emily White of the center’s public health sciences division, the researchers caution that this study needs to be confirmed before people start taking such supplements.

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

What that means is that this was a population study and did not directly compare a group of people given the supplement to a group that did not. Instead, they 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 National Cancer Institute’s Surveillance, Epidemiology and End Results cancer registry. When they analyzed the questionnaire results and compared the women diagnosed with breast cancer to the women who hadn’t they found that women in the study who regularly took fish oil supplements had a 32 percent lower risk of breast cancer.

White’s team noted that fish oil supplements contain high levels of the omega-3 fatty acids, EPA and DHA, and 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.

Although studies of omega-3 have shown inconsistent results, omega-3-containing fish oil continues to intrigue researchers, as evidence emerges about its protective effect on cardiovascular disease and now cancer.

Harvard researchers are currently enrolling patients for the randomized VITAL study, which will assess the impact of fish oil supplements and vitamin D on cancer, heart disease and stroke. The researchers plan to enroll 20,000 U.S. men aged 60 years and older and women aged 65 years and older who do not have a history of these diseases and have never taken supplements.

Recruitment for this National Institutes of Health funded study began in January, and more information can be found at www.vitalstudy.org.