The supplement is especially effective in post-menopausal women who have thicker breast tissue or who are overweight or obese.
Researchers from the Penn State Milton S Hershey Medical Centre tested the supplement against the anti-estrogen drug, Raloxifine, on a group of 266 post-menopausal women with no signs of breast cancer.
Over the two years the women took omega-3, their breast density reduced, although this was most noticeable in those with a body mass index (BMI) above 29, which is borderline obese.
The omega-3 contained 375 milligrams of DHA and 465 milligrams of EPA, the two fatty acids, although the researchers suspect that DHA is the more important fatty acid for reducing breast density.
Breast density is a key bio-marker for breast cancer