TORONTO, Canada--Researchers have discovered that a high-fiber grain cultivated since the times of the ancient Egyptians may delay the growth of cancerous tumors. In studies conducted on rats, Lilian Thompson, PhD, of the University of Toronto, found that a component isolated from flaxseed reduced mammary tumor growth by more than 50%.
Presenting her work at the annual meeting of the American Association for Cancer Research, Dr. Thompson said that flaxseed, also known as linseed, helps the body to produce animal lignans--diphenolic, small-molecule compounds that can affect hormone levels and have antioxidant and antitumor effects.
Plant Foods Tested for Lignan
Dr. Thompson and her team tested 66 different high-fiber grains, fruits, and vegetables for plant lignans, or lignan-like compounds, that the body can convert into usable animal lignans. She chose flaxseed because "it contains 75 to 800 times more lignan than any other plant food."
Flaxseed also contains an oil rich in alpha-linolenic acid, which is known to have anticancer effects. To determine the active ingredient that suppresses the growth of mammary tumors, Dr. Thompson fed flaxseed and/or secoisolariciresinol diglycoside (SD), the major animal lignan precursor extracted from flaxseed, to rats 13 weeks after they had been injected with a mammary carcinogen.
Dr. Thompson reported that after just 7 weeks, tumors in the animals that had received either flaxseed and/or the SD lignan grew at less than half the rate of the tumors in the control animals that did not get supplements. She also found that there were fewer and smaller new tumors in the group that received lignan.
"Lignan has characteristics that are similar to estrogen," Dr. Thompson said. She suspects that flaxseed lignan interferes with estrogen, limiting the body's ability to synthesize and reabsorb the hormone. She also surmises that lignan may inhibit the growth of blood vessels in the tumor, thus starving the tumor.