formononetin

PhytochemicalIsoflavoneBest with a meal

What is it

Formononetin is an isoflavone phytoestrogen found in red clover, soy, astragalus, and other legumes. It is sold as an isolated ingredient and as a standardized constituent of red clover extracts.

Evidence for 1 use

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

Menopausal symptoms

Limited Evidence

Red clover isoflavone extracts have shown small reductions in hot flash frequency in some randomized trials, but results are mixed and effect sizes modest.

How it works

Formononetin is a methylated isoflavone that is metabolized in the gut to daidzein and other isoflavones. Like other phytoestrogens it binds weakly to estrogen receptors, with preferential activity at ER-beta. Preclinical work suggests effects on bone, vascular tissue, and cancer cell lines through estrogen receptor and antioxidant pathways. Human data come mainly from red clover trials studying menopausal symptoms and bone density. Effects are modest and inconsistent across studies.

Dosage

DSLD does not report a standardized median dose for isolated formononetin. Red clover extracts typically supply 40-80 mg of total isoflavones per day, of which formononetin is one component. No RDA or upper limit has been set.

When and how to take it

Usually taken with food once daily.

2 commercial forms

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

Isolated formononetin

Used in research and a few premium supplements as a standalone isoflavone.

Demethylated in gut to daidzein

Red clover extract standardized to formononetin and other isoflavones

Most common consumer form.

Typical standardization is by total isoflavone percentage

Safety

Short-term use of red clover isoflavones is generally well tolerated. Reported side effects include headache, nausea, and breast tenderness. Long-term and high-dose safety, especially as an isolated isoflavone, is not well characterized.

Who should be cautious

Avoid in pregnancy and breastfeeding. People with a history of hormone-sensitive cancers (breast, uterine, ovarian) should consult a clinician before use. Use cautiously with anticoagulants or hormone-modulating medications.

Interactions

Possible additive effects with hormone therapy and tamoxifen. Theoretical interaction with anticoagulants given coumarin content of red clover.

Food sources

Red clover

Amount
Variable
%DV
—

Soybeans

Amount
Small amount
%DV
—

Chickpeas

Amount
Trace
%DV
—

Frequently asked questions

Is formononetin estrogenic?⌄

Yes, weakly. It binds to estrogen receptors and is considered a phytoestrogen, mostly through its metabolite daidzein.

Is it safe with a history of breast cancer?⌄

Caution is warranted. Anyone with a hormone-sensitive cancer history should consult their oncologist before using isoflavone supplements.

References

formononetin on Wikidata — Wikidata link

formononetin (ChEBI:18088) — ChEBI link

formononetin (PubChem CID 5280378) — PubChem link

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

Research on formononetin (PubMed search) — PubMed link

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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.