lignans

Lignans are a group of plant-derived polyphenolic compounds that are classified as secondary metabolites of vascular plants. They are characterized by their dibenzylbutane structure and are found throughout the plant kingdom, with particularly high concentrations in seeds, especially flaxseed, as well as in sesame, whole grains, vegetables, and fruits. The major dietary lignan in flaxseed is secoisolariciresinol diglucoside (SDG), which is converted by gut bacteria into enterolignans such as enterodiol and enterolactone, which are absorbed and circulated in the human body.

In humans, lignans act as phytoestrogens; their metabolites can weakly bind estrogen receptors and may exert estrogenic or antiestrogenic effects depending on physiological context. They also exhibit antioxidant and anti-inflammatory properties in some experimental settings. The health implications of lignan consumption remain uncertain: observational studies have linked higher lignan intake with various health outcomes, including lower risk of hormone-dependent cancers and cardiovascular disease, but randomized trials have not consistently confirmed substantial benefits.

Bioavailability of lignans depends on gut microbiota composition, food matrix, and processing. Processing and milling can affect lignan content in foods; fermentation and digestion are required to produce bioactive enterolignans. Analytical measurements often focus on urinary or plasma levels of enterolignans as biomarkers of exposure. No official daily intake is established, but a diet rich in plant-based foods provides lignans as part of a balanced pattern.