Blood levels of specific estrogens linked to increased risk for breast cancer "decreased significantly with flax" supplementation, according to Dr. Joanne Slavin of the University of Minnesota in St. Paul. She presented the findings here Wednesday at the annual meeting of the American Chemical Society.

Previous studies have suggested that naturally occurring compounds called phytoestrogens found in foods like flaxseed and soy work to lower levels of circulating estrogens linked to breast cancer. Flaxseed is especially high in one such phytoestrogen, lignan, which is thought to inhibit estrogen production.

In their study, Slavin's team tracked blood levels of two cancer-related estrogens, estrone sulfate and estradiol, in a group of 28 postmenopausal nuns over the course of one year. On top of their regular diet (which was similar for all the women studied), the nuns received daily supplements of either 0, 5 or 10 grams of ground flaxseed.

The researchers report that levels of the two circulating estrogens fell significantly among women taking the supplements, but remained stable in the non-supplement group.

Speaking to reporters, Slavin cautioned that the findings need to be duplicated in long-term studies before any definite recommendation regarding women and flaxseed consumption can be made.

But she believes that flax may soon join soy as a popular source of cancer-fighting compounds. Already, she said, many people "are starting to use flax as an alternative to soy because of its high levels of phytoestrogens."

Prior studies have suggested flaxseed may protect younger women from breast cancer, as well, Slavin said.

And last month, researchers reported in a small pilot study that a low-fat diet supplemented with flaxseed may reduce the growth of prostate cancer cells.