secoisolariciresinol

Secoisolariciresinol is a lignan, a type of plant polyphenol, found primarily in flaxseed. It serves as a precursor to the mammalian enterolignans, enterodiol and enterolactone, which are produced by intestinal bacteria from dietary lignans and may exert estrogen-like biological activity in humans.

Natural occurrence and chemical forms: In flaxseed the major lignan is secoisolariciresinol diglycoside (SDG), a glycoside that is hydrolyzed in the gut to the aglycone secoisolariciresinol. SDG and related lignans also occur in smaller amounts in other seeds, cereals, and plant-derived foods.

Biochemical properties and metabolism: After ingestion, SDG is de-glycosylated and converted by gut microbiota into secoisolariciresinol, which is further metabolized into enterodiol and then enterolactone. These metabolites are collectively known as enterolignans and can interact with estrogen receptors, producing tissue- and context-dependent hormonal effects.

Health relevance and evidence: Enterolignans have been studied for potential cardioprotective, anti-inflammatory, and anti-cancer effects, among other activities. Observational and interventional studies yield mixed results; some report modest associations with reduced risk of certain hormone-related cancers and favorable lipid or inflammatory profiles, while others show little or no effect. The mechanisms are not fully understood, and robust clinical evidence remains limited.

Safety, regulation, and use: Lignan-containing foods, particularly flaxseed, are generally considered safe as part of a balanced diet. Very high-dose supplements may interact with medications or hormone-sensitive conditions; individuals with such conditions should seek medical advice before taking lignan supplements.

Applications and research status: Secoisolariciresinol and SDG are used in flaxseed-derived functional foods and supplements. Ongoing research analyzes bioavailability, metabolism, and clinically meaningful outcomes to clarify potential health benefits.