Enterolactone

Pharmacology & Research

Enterolactone is the principal mammalian lignan — and the honest hinge of the whole page is that it is not a plant constituent. It is produced in the colon by gut bacteria from dietary plant lignans (matairesinol, secoisolariciresinol, lariciresinol and others, via enterodiol), and it is the molecule that “lignan/phytoestrogen” epidemiology actually measures: serum/urinary enterolactone is the validated biomarker of lignan and whole-grain/fibre intake. That makes two caveats load-bearing everywhere below — confounding (high enterolactone marks a plant-rich, high-fibre diet) and microbiome-dependence (antibiotics abolish its production). All human evidence is observational; there are no isolate trials.

1. Breast cancer (risk & prognosis)

The highest-evidence application — and the honest headline is that it is inconsistent. A pooled meta-analysis found a modest inverse association of enterolignans with breast-cancer risk restricted to postmenopausal women ^{4Reference 4Buck K et al. · 2010Meta-analysisMeta-analyses of lignans and enterolignans in relation to breast-cancer riskView study →}, while a well-powered prospective serum study found no protective association at all ^{5Reference 5Zeleniuch-Jacquotte A et al. · 2004Circulating enterolactone and risk of breast cancer: a prospective study in New YorkView study →}. For prognosis, higher enterolactone is associated with lower all-cause and breast-cancer mortality in postmenopausal patients ^{6,8Reference 6Seibold P et al. · 2014Meta-analysisEnterolactone concentrations and prognosis after postmenopausal breast cancer: effect modification and meta-analysisView study →Reference 8Micek A et al. · 2021Meta-analysisDietary phytoestrogens and biomarkers of their intake in relation to cancer survival and recurrence: a systematic review with meta-analysisView study →}, but one meta-analysis found the direction differs by menopausal status (postmenopausal benefit; a premenopausal signal toward higher mortality) ^{7Reference 7Liu Z et al. · 2021Meta-analysisLignan intake and enterolactone concentration and prognosis of breast cancer: a systematic review and meta-analysisView study →}.

Gap: entirely observational and biomarker-based — serum enterolactone co-tracks a high-fibre, plant-rich, lower-BMI, health-conscious phenotype, so residual confounding is unresolved, effect sizes are small, and no isolate RCTs exist ^{5,7Reference 5Zeleniuch-Jacquotte A et al. · 2004Circulating enterolactone and risk of breast cancer: a prospective study in New YorkView study →Reference 7Liu Z et al. · 2021Meta-analysisLignan intake and enterolactone concentration and prognosis of breast cancer: a systematic review and meta-analysisView study →}.

2. Cardiovascular & all-cause mortality

Low serum enterolactone was associated with higher risk of acute coronary events in a prospective Finnish study ^{9Reference 9Vanharanta M et al. · 1999ObservationalRisk of acute coronary events according to serum enterolactone: a prospective population-based case-control studyView study →} and with higher cardiovascular and all-cause mortality in the Kuopio cohort ^{10Reference 10Vanharanta M et al. · 2003Risk of cardiovascular-disease-related and all-cause death according to serum enterolactone: Kuopio Ischaemic Heart Disease Risk Factor StudyView study →}; higher enterolactone was associated with lower mortality among people with type 2 diabetes in a Danish cohort ^{11Reference 11Eriksen AK et al. · 2019ObservationalPre-diagnostic plasma enterolactone and lower mortality among individuals with type 2 diabetes: Danish Diet, Cancer and Health cohortView study →}.

Gap: the same biomarker confound in a different disease — enterolactone is a proxy for a high-fibre/Mediterranean dietary pattern that is independently cardioprotective, and no interventional evidence shows that raising enterolactone changes outcomes ^{9,10Reference 9Vanharanta M et al. · 1999ObservationalRisk of acute coronary events according to serum enterolactone: a prospective population-based case-control studyView study →Reference 10Vanharanta M et al. · 2003Risk of cardiovascular-disease-related and all-cause death according to serum enterolactone: Kuopio Ischaemic Heart Disease Risk Factor StudyView study →}.

3. Prostate cancer

The largest Nordic nested case-control study found no association between circulating enterolactone and prostate-cancer risk ^{12Reference 12Stattin P et al. · 2002ObservationalCirculating enterolactone and prostate-cancer risk: a Nordic nested case-control studyView study →}.

Gap: predominantly null, with small numbers and the same biomarker confound — included for honest completeness, not as a positive signal ^{12Reference 12Stattin P et al. · 2002ObservationalCirculating enterolactone and prostate-cancer risk: a Nordic nested case-control studyView study →}.

4. Weak SERM / phytoestrogen

Enterolactone binds ERα/ERβ weakly and behaves in a SERM-like (mixed agonist/antagonist) fashion ^{13Reference 13Cosentino M et al. · 2007Estrogenic activity of 7-hydroxymatairesinol potassium acetate and of its active metabolite enterolactone in MCF-7 cellsView study →}, and molecular modelling places lignans as aromatase (CYP19) ligands, supporting weak modulation of estrogen biosynthesis ^{14Reference 14Karkola S · 2009The binding of lignans, flavonoids and coumestrol to CYP450 aromatase: a molecular-modelling studyView study →}.

Gap: affinities are orders of magnitude below estradiol, the direction is concentration-dependent, and this is mechanistic, not clinical ^{13,14Reference 13Cosentino M et al. · 2007Estrogenic activity of 7-hydroxymatairesinol potassium acetate and of its active metabolite enterolactone in MCF-7 cellsView study →Reference 14Karkola S · 2009The binding of lignans, flavonoids and coumestrol to CYP450 aromatase: a molecular-modelling studyView study →}.

5. Antioxidant / anti-inflammatory

Enterolactone is described as a stronger radical scavenger than its parent lignans, and flaxseed lignan (SDG) reduces NF-κB signalling and mammary inflammation in models ^{15Reference 15Bowers LW et al. · 2019The flaxseed lignan secoisolariciresinol diglucoside decreases local inflammation, suppresses NF-κB signalling and inhibits mammary tumour growthView study →}.

Gap: preclinical only, and much of it is on precursor lignans rather than isolated enterolactone — a human flax-lignan trial found no change in antioxidant capacity ^{15Reference 15Bowers LW et al. · 2019The flaxseed lignan secoisolariciresinol diglucoside decreases local inflammation, suppresses NF-κB signalling and inhibits mammary tumour growthView study →}.

Mechanisms

Target / pathway	Effect	Relevant to
Gut microbiota (dehydroxylation/demethylation of plant lignans)	plant lignans → enterodiol → enterolactone	why it is a metabolite/biomarker; antibiotic abolition; huge inter-individual variability
ERα / ERβ	weak SERM-like binding (concentration-dependent)	phytoestrogen framing; hormone-cancer epidemiology
Aromatase (CYP19) / 17β-HSD	weak modelled modulation of estrogen biosynthesis	hormone-cancer mechanistic hypothesis
SHBG	proposed increase → lower free sex-hormone bioavailability	indirect hormone-cancer link (limited human data)
Radical scavenging; NF-κB	antioxidant; suppression in models (mostly parent lignans)	preclinical CVD/anti-inflammatory hypothesis

Pharmacokinetics

Enterolactone is not ingested — it is produced in the colon by gut bacteria from dietary plant lignans (matairesinol, secoisolariciresinol, lariciresinol, pinoresinol; the plant lignans → enterodiol → enterolactone) ^{1,2Reference 1Heinonen S et al. · 2001In-vitro metabolism of plant lignans: new precursors of the mammalian lignans enterolactone and enterodiolView study →Reference 2Wang LQ · 2002Mammalian phytoestrogens: enterodiol and enterolactoneView study →}. The enterolignans are then absorbed, undergo enterohepatic recirculation, are glucuronidated (and sulfated) in the liver, and are excreted in urine, with a plasma half-life on the order of ~12–24 h, so serum/urinary enterolactone reflects habitual rather than acute intake ^{2Reference 2Wang LQ · 2002Mammalian phytoestrogens: enterodiol and enterolactoneView study →}. The defining feature is enormous inter-individual variability driven by the microbiome: conversion efficiency depends on gut-flora composition, and broad-spectrum antibiotics sharply reduce or abolish production for weeks ^{3Reference 3Corona G et al. · 2023Interplay between lignans and gut microbiota: nutritional, functional and methodological aspectsView study →}. The same lignan intake yields very different enterolactone exposure between individuals — central to interpreting every association here.

Clinical trials

There are no interventional trials of isolated enterolactone in humans — by definition it is generated endogenously from dietary lignans by the microbiome, not administered as a drug. All human evidence is observational: prospective cohorts and nested case-control studies using serum/urinary enterolactone as a biomarker ^{4,5,6,7,8,9,10,11,12Reference 4Buck K et al. · 2010Meta-analysisMeta-analyses of lignans and enterolignans in relation to breast-cancer riskView study →Reference 5Zeleniuch-Jacquotte A et al. · 2004Circulating enterolactone and risk of breast cancer: a prospective study in New YorkView study →Reference 6Seibold P et al. · 2014Meta-analysisEnterolactone concentrations and prognosis after postmenopausal breast cancer: effect modification and meta-analysisView study →Reference 7Liu Z et al. · 2021Meta-analysisLignan intake and enterolactone concentration and prognosis of breast cancer: a systematic review and meta-analysisView study →Reference 8Micek A et al. · 2021Meta-analysisDietary phytoestrogens and biomarkers of their intake in relation to cancer survival and recurrence: a systematic review with meta-analysisView study →Reference 9Vanharanta M et al. · 1999ObservationalRisk of acute coronary events according to serum enterolactone: a prospective population-based case-control studyView study →Reference 10Vanharanta M et al. · 2003Risk of cardiovascular-disease-related and all-cause death according to serum enterolactone: Kuopio Ischaemic Heart Disease Risk Factor StudyView study →Reference 11Eriksen AK et al. · 2019ObservationalPre-diagnostic plasma enterolactone and lower mortality among individuals with type 2 diabetes: Danish Diet, Cancer and Health cohortView study →Reference 12Stattin P et al. · 2002ObservationalCirculating enterolactone and prostate-cancer risk: a Nordic nested case-control studyView study →}, plus flaxseed/lignan feeding studies that raise enterolactone and measure intermediate endpoints rather than clinical outcomes ^{15Reference 15Bowers LW et al. · 2019The flaxseed lignan secoisolariciresinol diglucoside decreases local inflammation, suppresses NF-κB signalling and inhibits mammary tumour growthView study →}. The entire clinical evidence base is associational, not causal.

Completed	Planned	Terminated	Observational (biomarker)
— (no isolate trial)	—	—	Extensive

Last checked: July 2026.

Toxicity & Safety

Enterolactone is effectively an endogenous metabolite of a normal plant-rich diet — anyone with lignan intake and an intact microbiome produces it continuously, and there is no toxicity signal at dietary exposures (and no isolate to dose). The only caution is theoretical and phytoestrogenic: because enterolactone has weak SERM-like ER activity, concentrated/supplemental phytoestrogen use warrants caution in hormone-sensitive conditions (ER-positive breast cancer, endometrial disease), and the premenopausal-prognosis signal in one meta-analysis ^{7Reference 7Liu Z et al. · 2021Meta-analysisLignan intake and enterolactone concentration and prognosis of breast cancer: a systematic review and meta-analysisView study →} is a reason not to over-encourage high-dose lignan supplementation. This is precautionary, not evidence of harm at food intakes. Note a microbiome interaction rather than a toxicity: antibiotics markedly reduce enterolactone formation, blunting any expected benefit.

Pregnancy & lactation

Dietary lignans fine; avoid supplements. Enterolactone from ordinary dietary lignans (flaxseed, whole grains, seeds, vegetables) at normal food amounts is part of a routine diet and not a specific concern, but because it is a phytoestrogen with weak ER activity, concentrated flax-lignan or enterolactone-boosting supplements should be avoided in pregnancy and lactation on precautionary hormonal grounds — supplemental safety is not established.

Dosage

No therapeutic dose exists and none is recommended. Enterolactone cannot be meaningfully “dosed” — it is produced by the individual’s gut flora from dietary lignans at a microbiome-set rate. The relevant exposure is dietary lignan intake (flaxseed is by far the richest common source; sesame, whole grains/rye, other seeds, legumes and vegetables also contribute), and serum enterolactone is used as a research biomarker, not a target to titrate.

References