Lignans

PhytochemicalLignanBest with a meal

What is it

Lignans are a class of plant polyphenols found especially in flaxseed, sesame seeds, and whole grains. The main dietary lignan, secoisolariciresinol diglucoside (SDG), is converted by gut bacteria to enterolignans (enterodiol, enterolactone) with weak estrogenic activity.

Evidence for 2 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Cardiovascular markers

Good Evidence

Flaxseed and lignan consumption modestly improves lipid profile (LDL, total cholesterol) in multiple trials.

Menopausal symptoms

Limited Evidence

Small clinical trials show modest reductions in hot flashes with flaxseed or lignan supplementation, though effects are smaller than HRT or soy isoflavones.

How it works

Enterolignans are phytoestrogens with weak binding to estrogen receptors, producing mild estrogenic or antiestrogenic effects depending on tissue and context. Lignans also have antioxidant activity and may influence sex hormone metabolism. Clinical evidence suggests modest effects on menopausal symptoms, lipid profile, and possibly hormone-related cancer risk. Effects on hot flashes are smaller than soy isoflavones or hormone replacement.

Dosage

Dietary lignan intake from flaxseed: 1-2 tablespoons of ground flax (10-25 mg of SDG). SDG supplements typically deliver 50-300 mg per day.

When and how to take it

WHEN: With meals; daily consistency over weeks matters. HOW: Mix ground flaxseed into food, or take SDG capsules with water and food.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Ground flaxseed

Most accessible dietary source.

Whole-food source providing SDG plus fiber and omega-3s.

SDG extract

Used in supplements for higher-dose intake.

Concentrated lignan content; converted to enterolignans by gut bacteria.

Safety

Generally safe at dietary amounts. Side effects of supplements include mild GI upset. High doses in hormone-sensitive conditions are debated. Flaxseed (whole or ground) is well tolerated.

Who should be cautious

Discuss with clinician if you have hormone-sensitive cancer history or take tamoxifen. Use cautiously in pregnancy with high-dose isolated SDG supplements.

Interactions

Possible interactions with tamoxifen and other hormone-modulating drugs. May enhance anticoagulant effects at very high intakes. Theoretical interaction with thyroid medications.

Food sources

Ground flaxseed

Amount
1 tablespoon (7 g)
%DV
—

Sesame seeds

Amount
1 tablespoon (9 g)
%DV
—

Frequently asked questions

Are lignans the same as omega-3?⌄

No. Both are found in flaxseed but are different compounds. Omega-3 (ALA) is a fatty acid; lignans are polyphenols. Flax oil has the omega-3 but is low in lignans.

Are lignan supplements safer than soy isoflavones?⌄

Both are phytoestrogens. Lignans bind to estrogen receptors more weakly than isoflavones. Safety considerations are similar; discuss with clinician for hormone-sensitive conditions.

References

Lignans on Wikidata — Wikidata link

Lignans (ChEBI:25036) — ChEBI link

Lignans on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Lignans (PubMed search) — PubMed link

Track Lignans with Pilora

Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.