Enterodiol

Pharmacology & Research

Enterodiol is a mammalian lignan (an “enterolignan”) — and, like enterolactone, it is not a plant constituent. It is produced in the colon by gut bacteria from dietary plant lignans (chiefly secoisolariciresinol, also matairesinol and lariciresinol) and is frequently oxidised further to enterolactone — so it is best understood as an intermediate on the way to enterolactone, and the less-studied half of the pair. Almost all human epidemiology measures enterolactone (sometimes both), not enterodiol alone, so its own evidence is thin and mostly shared or preclinical.

1. Mammalian-lignan / phytoestrogen

Enterodiol is, with enterolactone, the endpoint of gut conversion of dietary lignans and is classed as a mammalian phytoestrogen ^{1Reference 1Wang LQ · 2002Mammalian phytoestrogens: enterodiol and enterolactoneView study →}; in human-cell ER assays the enterolignans show weak, mixed agonist/antagonist activity on ERα and ERβ ^{5,6Reference 5Mueller SO et al. · 2004Phytoestrogens and their human metabolites show distinct agonistic and antagonistic properties on ERα and ERβ in human cellsView study →Reference 6Rietjens IMCM et al. · 2017The potential health effects of dietary phytoestrogensView study →}.

Gap: binding is weak and generally less characterised than enterolactone, and there are no clinical endpoints for enterodiol as an isolate — the phytoestrogen signal is measured on circulating enterolactone from mixed lignan intake ^{5Reference 5Mueller SO et al. · 2004Phytoestrogens and their human metabolites show distinct agonistic and antagonistic properties on ERα and ERβ in human cellsView study →}.

2. Cancer (preclinical & shared biomarker)

Enterodiol appears in preclinical anticancer work on flaxseed-lignan metabolites ^{7Reference 7De Silva SF · 2023Anticancer potential of flaxseed lignans, their metabolites and synthetic counterparts in relation to molecular targetsView study →}, and an enterodiol-inclusive mouse study found the enterolignans (alone and with genistein) did not promote MCF-7 xenograft growth ^{8Reference 8Power KA et al. · 2006AnimalMammalian lignans enterolactone and enterodiol, alone and with genistein, do not promote the growth of MCF-7 xenografts in ovariectomised athymic nude miceView study →}. Human hormone-cancer epidemiology is on enterolactone (prospective breast-cancer study; a prognosis meta-analysis mixed by menopausal status) ^{9,10Reference 9Zeleniuch-Jacquotte A et al. · 2004Circulating enterolactone and risk of breast cancer: a prospective study in New YorkView study →Reference 10Liu Z et al. · 2021Meta-analysisLignan intake and enterolactone concentration and prognosis of breast cancer: a systematic review and meta-analysisView study →}.

Gap: preclinical plus shared-biomarker only — no study isolates enterodiol’s human contribution, and enterolactone’s epidemiology is deliberately not double-counted here ^{9,10Reference 9Zeleniuch-Jacquotte A et al. · 2004Circulating enterolactone and risk of breast cancer: a prospective study in New YorkView study →Reference 10Liu Z et al. · 2021Meta-analysisLignan intake and enterolactone concentration and prognosis of breast cancer: a systematic review and meta-analysisView study →}.

3. Antioxidant

As a dihydroxy dibenzylbutane polyphenol, enterodiol has expected in-vitro radical-scavenging capacity, discussed at the enterolignan-class level ^{1,6Reference 1Wang LQ · 2002Mammalian phytoestrogens: enterodiol and enterolactoneView study →Reference 6Rietjens IMCM et al. · 2017The potential health effects of dietary phytoestrogensView study →}.

Gap: in-vitro/class-level only, with enterolactone the more-studied and often stronger antioxidant of the pair, and no human antioxidant-outcome data for enterodiol ^{1,6Reference 1Wang LQ · 2002Mammalian phytoestrogens: enterodiol and enterolactoneView study →Reference 6Rietjens IMCM et al. · 2017The potential health effects of dietary phytoestrogensView study →}.

4. Anti-proliferative

Enterodiol is included among flaxseed-lignan metabolites reported to modulate proliferation in cancer cell models ^{7Reference 7De Silva SF · 2023Anticancer potential of flaxseed lignans, their metabolites and synthetic counterparts in relation to molecular targetsView study →}.

Gap: all in-vitro, frequently at supraphysiologic concentrations, usually reported jointly with enterolactone, with no isolate clinical anticancer evidence ^{7Reference 7De Silva SF · 2023Anticancer potential of flaxseed lignans, their metabolites and synthetic counterparts in relation to molecular targetsView study →}.

Mechanisms

Target / pathway	Effect	Relevant to
ERα / ERβ	weak, tissue-selective SERM-like binding	phytoestrogen role; hormone-cancer rationale
Gut microbiota (dehydroxylation/demethylation → oxidation)	plant lignans → enterodiol → enterolactone	its precursor→product identity (an intermediate frequently oxidised onward)
Radical scavenging (phenolic H-donation)	antioxidant in vitro (class-level)	antioxidant
Tumour-cell proliferation pathways	anti-proliferative in cell models	preclinical anticancer

Pharmacokinetics

Enterodiol is not ingested — it is produced in the colon by gut bacteria from dietary plant lignans (principally secoisolariciresinol, also matairesinol) ^{1,2Reference 1Wang LQ · 2002Mammalian phytoestrogens: enterodiol and enterolactoneView study →Reference 2Heinonen S et al. · 2001In-vitro metabolism of plant lignans: new precursors of the mammalian lignans enterolactone and enterodiolView study →}. Once formed it is absorbed, undergoes enterohepatic recirculation and glucuronidation/sulfation, and is excreted in urine; a portion is further oxidised by gut bacteria to enterolactone, so enterodiol is best understood as an intermediate on the way to enterolactone ^{1,2Reference 1Wang LQ · 2002Mammalian phytoestrogens: enterodiol and enterolactoneView study →Reference 2Heinonen S et al. · 2001In-vitro metabolism of plant lignans: new precursors of the mammalian lignans enterolactone and enterodiolView study →}. Isolated bacterial strains that convert secoisolariciresinol to enterodiol have been characterised ^{3Reference 3Zhu Y et al. · 2024Bioconversion of lignans in flaxseed cake and isolation of an Enterococcus faecium strain converting secoisolariciresinol diglucoside to enterodiolView study →}. Formation is strongly microbiome-dependent and varies widely between individuals; antibiotics sharply reduce enterolignan production, and enterodiol and enterolactone together are the serum/urinary biomarkers of dietary-lignan intake (enterolactone the more commonly reported) ^{4Reference 4Corona G et al. · 2023Interplay between lignans and gut microbiota: nutritional, functional and methodological aspectsView study →}.

Clinical trials

There are no interventional trials of enterodiol as an isolate. It is measured only as a diet-derived biomarker within enterolignan/phytoestrogen observational studies (which predominantly report enterolactone) ^{9,10Reference 9Zeleniuch-Jacquotte A et al. · 2004Circulating enterolactone and risk of breast cancer: a prospective study in New YorkView study →Reference 10Liu Z et al. · 2021Meta-analysisLignan intake and enterolactone concentration and prognosis of breast cancer: a systematic review and meta-analysisView study →}, and the preclinical evidence is modest — cell models plus one mouse xenograft study showing no tumour promotion ^{7,8Reference 7De Silva SF · 2023Anticancer potential of flaxseed lignans, their metabolites and synthetic counterparts in relation to molecular targetsView study →Reference 8Power KA et al. · 2006AnimalMammalian lignans enterolactone and enterodiol, alone and with genistein, do not promote the growth of MCF-7 xenografts in ovariectomised athymic nude miceView study →}.

Completed	Planned	Terminated	Observational / preclinical
— (no isolate trial)	—	—	Modest (mostly shared with enterolactone)

Last checked: July 2026.

Toxicity & Safety

Enterodiol is an endogenous product of normal gut metabolism of ordinary lignan-containing foods (flaxseed, sesame, whole grains, seeds, vegetables), with a long history of everyday internal exposure and no toxicity signal at dietary intakes — hence [low]. There is no toxicity characterisation of concentrated/supplemental enterodiol (no human isolate data). The phytoestrogen caution is theoretical: weak ER activity means isolated/supplemental phytoestrogen use warrants caution in hormone-sensitive conditions (ER-positive breast cancer, endometrial issues) — precautionary, not evidence of harm at food levels (a mouse study found the enterolignans did not promote MCF-7 xenograft growth ^{8Reference 8Power KA et al. · 2006AnimalMammalian lignans enterolactone and enterodiol, alone and with genistein, do not promote the growth of MCF-7 xenografts in ovariectomised athymic nude miceView study →}). Note a microbiome interaction rather than a toxicity: antibiotics markedly reduce enterolignan formation.

Pregnancy & lactation

Dietary lignans fine; avoid the isolated phytoestrogen. Dietary lignans from ordinary foods are generally considered fine in pregnancy and lactation, but isolated/supplemental enterodiol (or lignan phytoestrogen concentrates) is not recommended — avoid — given weak estrogenic activity and the absence of safety data.

Dosage

There is no established therapeutic dose and no validated human dose — enterodiol is not taken directly but generated internally from dietary lignan intake at a rate set by the individual’s gut flora (flaxseed is the richest common substrate; sesame, whole grains, seeds and vegetables also contribute). Any supplement figures would be research references, not recommendations.

References