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.