Lignans are naturally occurring chemicals widespread within
the plant and animal kingdoms. Several lignans—with intimidating names such as
secoisolariciresinol—are considered to be phytoestrogens, plant chemicals that
mimic the hormone estrogen. These are especially abundant in flaxseeds and sesame
seeds. (Although flaxseed oil
contains Omega 3, it does not contain the lignan and fiber as found in the
flaxseed. The lignans and fiber are removed during the process of making
Bacteria in our intestines convert the naturally occurring
phytoestrogens from flaxseed into two other lignans, enterolactone and
enterodiol, which also have estrogen-like effects.
Lignans are being studied for possible use in cancer
prevention, particularly breast cancer. Like other phytoestrogens (such as soy isoflavones), they
hook onto the same spots on cells where estrogen attaches. If there is little
estrogen in the body (after menopause, for example), lignans may act like weak
estrogen; but when natural estrogen is abundant in the body, lignans may
instead reduce estrogen's effects by displacing it from cells. This
displacement of the hormone may help prevent those cancers, such as breast
cancer, that depend on estrogen to start and develop. In addition, at least one
test tube study suggests that lignans may help prevent cancer in ways that are
unrelated to estrogen.
The richest source of lignans is flaxseed (sometimes called
linseed), containing more than 100 times the amount found in other foods! Flaxseed oil,
however, does not contain appreciable amounts of lignans. Sesame seed is an
equally rich source. Other food sources are pumpkin seeds, whole grains,
cranberries, and black or green tea. Cooking flaxseed apparently does not decrease the amount of
lignans absorbed by the body.
A number of preliminary human and animal studies suggest
that lignans may be helpful for cancer
prevention , particularly of breast and colon cancer, as well
reduction of cholesterol. Other highly preliminary research suggests that
flaxseeds or lignans may decrease menopausal symptoms and improve kidney
function in various types of kidney disease.
The most promising use for lignans is in cancer prevention.
According to observational studies, people who eat more lignan-containing foods have a lower incidence of
breast and perhaps colon cancer. This, however, does not prove that lignans are
the cause of the benefit, for other factors in these foods, or in the characteristics
of the people who consume these foods, may have been responsible.