Enterodioli

Enterodioli are lignan-derived metabolites produced by the human gut microbiota from dietary plant lignans. The primary circulating compound is enterodiol, which can be further oxidized to enterolactone. These enterolignans are considered phytoestrogens because they can bind estrogen receptors with weak affinity and may exert estrogen-like or anti-estrogenic effects depending on hormonal context.

Metabolism and sources: Dietary lignans such as secoisolariciresinol and matairesinol are ingested; gut bacteria convert them to enterodiol, which is absorbed and subsequently conjugated in the liver to glucuronide or sulfate forms before excretion in urine or bile. Enterodiol can be further metabolized to enterolactone by microbial enzymes. Flaxseed is a particularly rich source of lignans, with other seeds, whole grains, and certain vegetables contributing as well. The amount of circulating enterodiols varies with diet and with an individual’s gut microbiome, and they are often used as biomarkers of lignan intake.

Biological relevance and evidence: Because of their interaction with estrogen receptors, enterodiol and enterolactone are studied for potential roles in cancer risk reduction, cardiovascular health, and menopausal symptom management. Evidence from observational studies is mixed and often inconclusive, and interindividual differences in gut microbiota substantially influence levels and responses. Mechanistic data support weak estrogenic activity and antioxidant properties in some models, but clinical implications remain uncertain.

Measurement and variability: Plasma and urinary levels reflect intake plus microbial conversion efficiency and are influenced by factors such as age, sex, antibiotic use, and geography.