enterolactone

Enterolactone is a mammalian lignan produced in the human gut by microbial metabolism of dietary plant lignans, especially secoisolariciresinol and matairesinol. After ingestion, these lignans are converted by intestinal bacteria first to enterodiol and then to enterolactone. The compound is absorbed and circulates in the bloodstream mostly as conjugates (glucuronides or sulfates) and is excreted in urine, where its levels can reflect exposure to dietary lignans.

Biological activity of enterolactone is that of a phytoestrogen with relatively weak estrogenic activity and a tendency to interact with estrogen receptors, sometimes showing a preference for ERβ in experimental assays. It may modulate hormone signaling in tissues and has been reported to possess antioxidant, anti-inflammatory, and antiproliferative properties in various in vitro systems. Its effects can be context-dependent and are generally milder than those of endogenous estrogens.

Health research on enterolactone in humans yields mixed results. Some observational studies associate higher circulating enterolactone levels or greater lignan intake with potential reductions in risk for certain hormone-related cancers and improvements in cardiovascular risk markers, but findings are inconsistent and may be confounded by overall diet and lifestyle. Randomized trials of flaxseed or lignan-rich diets have produced variable effects on menopausal symptoms, lipid profiles, and inflammatory markers.

Dietary sources of enterolactone precursors include flaxseed, sesame seeds, whole grains, and some vegetables. Production depends on the composition and activity of an individual’s gut microbiota, which determines the efficiency of conversion from plant lignans to enterolactone. Mechanistic and epidemiological evidence remains exploratory, and enterolactone is often used as a biomarker of lignan exposure rather than a proven therapeutic agent.