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 the oil).
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.