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There is promising news on the cancer front. Research released this week suggests that fish oil supplements may help guard against some types of breast cancer.

But the lead author of the study is quick to add a few words of caution. "This is only one study. And we don't rely on just one study to make a recommendation" to start taking fish oil to stave off breast cancer, says Emily White of the Fred Hutchinson Cancer Research Center in Seattle.

Still, the findings are intriguing and bound to fuel more interest in the already popular fish oil supplements, which are also thought to help curb the risk of heart disease.

The study involved more that 35,000 postmenopausal women who completed a questionnaire about their use of non-vitamin, non-mineral, supplements. Aside from fish oil, the list of supplements also included acidophilus, black cohosh, chondroitin, dong quai, garlic pills, ginkgo biloba, ginseng, glucosamine, melatonin, methylsulfonylmethane, soy and St. John's wort.

After six years of follow-up, a total of 880 women were diagnosed with breast cancer. The researchers then analyzed the data to see if taking any of the supplements bestowed some protection against breast cancer.

Only fish oil stood out. Regular use of this supplement – which contains high levels of omega-3 and other fatty acids – was linked to a 32 per cent reduced risk of breast cancer, according to the findings published in the journal Cancer Epidemiology, Biomarkers & Prevention. But the protection applied to only invasive ductal carcinoma, the most common type of breast cancer. (The second most common form is called invasive lobular carcinoma and it tends to be driven by hormones.)

In theory, at least, fish oil may provide a partial shield against cancer through its anti-inflammatory properties. "Inflammation causes cells to divide and proliferate and when cells divide that provides the opportunity for genetic errors to accumulate and that leads to cancer," Dr. White said. "So there is pretty of good evidence that inflammation is involved in cancer and fish oil [may act as] an anti-inflammatory drug."

Meanwhile, researchers at Harvard University are launching a major clinical trial to assess omega-3. When those results are in, likely several years from now, doctors and patients will have a better idea if fish oil really can help prevent breast cancer.