The mammalian lignans, enterodiol and enterolactone (see chemical structures), are formed by the action of intestinal bacteria on lignan precursors found in plants (1). Because enterodiol and enterolactone can mimic some of the effects of estrogens, their plant-derived precursors are classified as phytoestrogens. Lignan precursors that have been identified in the human diet include pinoresinol, lariciresinol, secoisolariciresinol, matairesinol, and others (see chemical structures). Secoisolariciresinol and matairesinol were among the first lignan precursors identified in the human diet and are therefore, the most extensively studied. Lignan precursors are found in a wide variety of foods including flaxseeds, legumes, whole grains, fruits and vegetables. While most research on phytoestrogen-rich diets has focused on soy isoflavones, lignans are the principal source of dietary phytoestrogens in typical Western diets (2, 3).
* Lignan precursors are found in a wide variety of plant-based foods, including seeds, whole grains, legumes, fruits and vegetables.
* Flaxseeds are the richest dietary source of lignan precursors.
* When consumed, lignan precursors are converted to the mammalian lignans, enterodiol and enterolactone, by bacteria that normally colonize the human intestine.
* Enterodiol and enterolactone have weak estrogenic activity but may also exert biological effects through nonestrogenic mechanisms.
* Lignan-rich foods are part of a healthy dietary pattern, but the role of lignans in the prevention of hormone-associated cancers, osteoporosis, and cardiovascular diseases is not yet clear.
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