Soy Isoflavones
Also known as: Genistein + Daidzein, Soy extract 40%, Phytoestrogens
Isoflavones bind oestrogen receptors (preferentially ER-beta) with weak activity. Meta-analyses of RCTs show a small but real reduction in hot-flush frequency; individual response depends partly on gut conversion of daidzein to equol, which only a minority of people produce.
Last reviewed: 2026-10-06 · 0 indexed studies
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Overview
Soy isoflavones (genistein, daidzein, glycitein) are phytoestrogens standardised in extracts (commonly 40%). The best evidence supports modest reduction of menopausal hot flushes; effects on bone and cardiovascular markers are less consistent.
Mechanism & Function
Mechanism of Action
Selective oestrogen-receptor modulation (ER-beta preferring), with additional antioxidant and tyrosine-kinase-modulating effects shown preclinically.
Physiological Role
No physiological role; dietary phytoestrogens.
Primary Pathways
Performance / Health Relevance
No performance relevance; positioned for menopausal symptom support.
Evidence Review
No human clinical studies indexed for this ingredient yet.
No meta-analyses or systematic reviews indexed for this ingredient yet.
Dimensions marked N/A have no indexed evidence of that class. They are shown as unavailable rather than scored.
Practical Use & Dosage
- Minimum Effective Dose
- ~40–50 mg isoflavones/day
- Optimal Range
- 40–80 mg/day
- Upper / Caution Level
- Up to ~100 mg/day used in trials; long-term high-dose data limited
- Timing
- Daily, divided doses
- Best Format
- Extract standardised for total isoflavones (e.g. 40%)
- Bioavailability
- Glycoside forms are hydrolysed by gut bacteria; equol-producer status affects response.
- Absorption Considerations
- Effects on hot flushes typically take 4–12 weeks to emerge.
Safety & Interactions
Side Effects
- •Mild GI upset
Contraindications
- Oestrogen-sensitive conditions (discuss with a clinician)
- Pregnancy
Drug Interactions
- •Tamoxifen and aromatase inhibitors (theoretical opposition)
- •Thyroid medication (soy can reduce absorption — separate timing)
Who Should Avoid
- •People with oestrogen-receptor-positive conditions without medical advice
Monitoring
Separate from levothyroxine by several hours.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is Soy Isoflavones typically used or indicated?
Soy Isoflavones is most commonly used for: Menopause-support formulas, Women's-health supplements, Bone-health blends. No physiological role; dietary phytoestrogens.
How does Soy Isoflavones work?
Selective oestrogen-receptor modulation (ER-beta preferring), with additional antioxidant and tyrosine-kinase-modulating effects shown preclinically.
What is the recommended dose of Soy Isoflavones?
The optimal range is 40–80 mg/day. with a minimum effective dose of ~40–50 mg isoflavones/day. Best taken: Daily, divided doses. Upper / caution level: Up to ~100 mg/day used in trials; long-term high-dose data limited.
What are the side effects of Soy Isoflavones?
Reported side effects include: Mild GI upset. Monitoring: Separate from levothyroxine by several hours.
Does Soy Isoflavones interact with medications?
Known or theoretical interactions: Tamoxifen and aromatase inhibitors (theoretical opposition); and Thyroid medication (soy can reduce absorption — separate timing). Always check with a clinician before combining with prescription medication.
Who should avoid Soy Isoflavones?
Soy Isoflavones is generally not recommended for: People with oestrogen-receptor-positive conditions without medical advice; Oestrogen-sensitive conditions (discuss with a clinician); and Pregnancy.
How strong is the evidence for Soy Isoflavones?
Evidence level: Limited (overall score 40/100), based on 0 indexed studies on SuppIndex.
Research & References (0)
No studies match this filter
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Research Overview
Limited EvidenceCite this ingredient
One-click citation export in APA, MLA, Chicago, BibTeX, or HTML. The URL below is stable and safe to link.
Stable URL
https://thesuppindex.com/ingredients/soy-isoflavones
SuppIndex. (2026). Soy Isoflavones: Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/soy-isoflavones
Based on 0 indexed studies · Evidence level: Limited.
Goal Ratings
Stack Compatibility
Combined with red clover or black cohosh in menopause formulas.