Nutrition Bytes

The flax plant (Linum usitatissimum) is an annual herb. The seeds are also one of the richest dietary sources of phytoestrogens (estrogenic compounds derived from plants). Because flaxseed is the richest dietary source of lignans, it has been used to investigate the potentially anticarcinogenic effects of lignans in animal studies and some human trials. The plant lignan secoisolariciresinol diglycoside (SDG) has been suggested to be the primary effector of the antitumorigenic effects of flaxseed observed in vitro with mammary and colon carcinogenesis models. Proposed mechanisms to date for the observed inhibition of tumor growth have included estrogenic and antiestrogenic effects, anti-oxidative effects, antiproliferative and anti-aromatase effects. This review addresses some of the animal and human studies of flaxseed’s anticarcinogenic effects in breast, melanoma, and prostate cancers. The data on possible antitumorigenic effects of flaxseed in humans are inconclusive at best, however, in vitro data suggest that SDG as an anticarcinogenic agent warrants further study. Its potential mechanism of action in cancer prevention remains unclear. Flaxseed supplementation for its own sake is harmless, however, and potentially beneficial in other ways not addressed by this review.