Definition

A group of bioactive polyphenolic phytoestrogens derived from the seed of the flax plant (Linum usitatissimum) with potential antioxidant and chemopreventive activities. Flaxseed lignan is primarily comprised of secoisolariciresinol diglucoside (SDG), isolariciresinol, matairesinol, pinoresinol and lariciresinol. SDG is converted to the enterolignans enterolactone (EL) and enterodiol (ED) by the intestinal microflora in the proximal colon. EL and ED have both weakly estrogenic and anti-estrogenic activities depending upon the tissue. The anti-estrogenic effects in reproductive tissue may help reduce the risk of hormone-associated cancers, while the estrogenic effects in bone may help maintain bone density. Flaxseed is the richest dietary source of lignans.