THE DETAILS: Researchers looked at non-vitamin, non-mineral "specialty" supplement use of more than 35,000 postmenopausal women and discovered that those who regularly used fish oil supplements were one-third less likely to develop breast cancer than those who did not use fish oil. "We looked at days per week and years of use, but not dose per day," says study author Emily White, PhD, an investigator at the Fred Hutchinson Cancer Center and professor of epidemiology at the University of Washington, both in Seattle. She noted that most women who used fish oil at the time they entered the study (in the low-risk group) took it four to seven times a week.
"Risk of breast cancer did not vary by years of use," she added. Researchers also found a lower breast cancer risk in higher-risk women (older age, obesity, heavy drinking, and physical inactivity are believed to put women at a higher risk) who reported taking fish oil supplements.
The study author also looked at 14 other non-vitamin, non-mineral supplements and found that no others were related to breast cancer risk. In addition, researchers also found that use of supplements sometimes taken for menopausal symptoms, including black cohosh, dong quai, soy, and St. John's wort, were not associated with breast cancer risk.
WHAT IT MEANS: White says the strength of evidence across all studies is not sufficient for a public health recommendation directing women to take fish oil supplements to prevent breast cancer. And though this study shows promise and warrants further research into the use of fish oil to prevent breast cancer, it's important to note that this was an observational study, so it does not show a cause-and-effect type of relationship that could provide more concrete evidence of a benefit. Still, mounting research suggests a whole slew of health benefits from incorporating omega-3 fatty acids into our diet, including protection against colon cancer and heart disease. (Need ideas? Here are five recipes rich in omega-3s to get you started.)
Flaxseeds, a vegetarian source of omega-3 fatty acids, are chockfull of another type called ALA, which partially converts to DHA and EPA (although the efficiency of the transformation varies, depending on which expert you ask).
Here's what you need to know to reduce breast cancer risk:
• Find the right fish. Omega-3 fatty acids in fish oil supplements are known to calm inflammation, which raises the risk of all sorts of chronic diseases. While it's often best to get your nutrients from whole food sources, i.e., real fish, if you choose to go the supplement route, make sure you read our story on Best Fish Oil Supplements. Whether you're looking at a pill or a real fish entrée, it's important to choose a fish that's lower in contaminants, and species that aren't overfished. Sardines (Vital Choice uses BPA-free cans), anchovies, wild-caught Alaskan salmon, or mackerel. The Superfish List also reveals the greenest, healthiest seafood picks on the planet.
• Eliminate other risk factors. Make healthy to decrease your risk of developing breast cancer. "Women should not take combined hormone replacement therapy (estrogen plus a progestin), or should only take it for a short time," says White. "They should maintain a normal weight and limit alcohol intake."
Exercise has been shown to lower breast cancer risk. In fact, a study published in 2008 in the Clinical Journal of Oncology found that women who exercised a year before diagnosis were 30 percent more likely to survive the disease.