Flaxseed is one of the richest sources of lignans, a type of phytoestrogen. Phytoestrogens are a diverse group of plant-derived compounds that can interfere with estrogen metabolism in animals and humans. In fact, phytoestrogens may have contrary biological effects, exhibiting both estrogen and antiestrogen activity.

Lignans have numerous biological properties, including antimitotic, antifungal and antioxidant activities. Lignans from pine cones and the creosote bush have been shown to inhibit replication of the human immunodeficiency virus in-vitro. A newly identified lignan, cinnamophilin, inhibits thromboxane synthase, which decreases thromboxane A2 production and thereby reduces platelet aggregation and vasoconstriction. Flaxseed and other lignans are currently being investigated for their anticancer properties.

What Are the Major Food Sources of Lignans?

Lignans are widely distributed in the plant kingdom, being found in most unrefined grains such as barley, buckwheat, millet, and oats; legumes such as soybeans; and some vegetables such as broccoli, carrots, cauliflower and spinach. The richest source of lignans is flaxseed. Flaxseed contains high levels of the plant lignan precursor, secoisolariciresinol diglycoside(SDG), and provides 75-800 times more plant lignans than most other foods found in vegetarian diets. Most flaxseed lignans are removed during processing and thus are not found in appreciable quantities in flaxseed oil.