Soy Isoflavones for Hot Flashes

Verdict: Published with Warning

Across 7 PubMed studies, the evidence for Soy Isoflavones in Hot Flashes grades Tier B — preliminary evidence. Effective, but with safety or population caveats.

B 🟡 B Preliminary Evidence Published with Warning

🔬Why this grade7-layer evidence engine

⚖️

Scoring transparency

All scores computed by a 7-layer evidence engine — fully auditable

Raw score 0.41

← counter-evidence / ineffectiveeffective / strong evidence →

Final grade

B · Published with Warning

Confidence

66%

Broadly consistent

Evidence level

Cochrane high-quality SR/MA

How strongly each layer supports this effect

lower = less supportive

L5 Clinical bodiesAuthoritative stance

0.26

L2 PubMedPrimary literature

0.45

L3 MechanismPlausibility

0.45

L1 ExamineGlobal benchmark

0.50

L11 AI re-checkIndependent read

0.65

Against Mixed Supports

▸View the full decision path (audit trail)

compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.406
tier_from_score — 依分數區間映射至 tier letter
apply_hec_rules — 高品質 SR/MA 內部嚴重矛盾 (3 positive vs 2 negative，各 ≥2)
tier_strict_requirement_check — Tier 條件達標，未降階
detect_disputes — 偵測到 1 個 hard + 1 個 soft dispute
decide_status — 依 tier + dispute 結果決定 status

📄PubMed studies (7)L2 · primary research & systematic reviews

Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and

PMID: 22433977 2012 統合分析 n = 19

Finding: Isoflavones reduced hot flash frequency by 20.6% (95% CI -28.4 to -12.9; p<0.00001) and severity by 26.2% (95% CI -42.2 to -10.2; p=0.001) vs placebo.

🟢 High quality Effect size: Frequency: -20.6%; Severity: -26.2%

View on PubMed

Quantitative efficacy of soy isoflavones on menopausal hot flashes

PMID: 25316502 2015 統合分析 n = 16

Finding: Net efficacy (after placebo subtraction) was 25.2% maximum reduction; requires 13.4 weeks to reach half-maximal effect vs 3.09 weeks for estradiol; full effect requires ≥48 weeks.

🟢 High quality Effect size: Max net effect: 25.2% reduction; 57% of estradiol efficacy

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Soy isoflavones versus placebo in the treatment of climacteric vasomotor symptoms: systematic review and meta-analysis

PMID: 20464785 2010 統合分析 n = 19

Finding: Overall SMD -0.39 (95% CI -0.53 to -0.25) favoring soy; high heterogeneity prevents conclusive interpretation. Extracts showed stronger effect (SMD -0.51) vs dietary supplements (SMD -0.20).

Effect size: SMD -0.39 (95% CI -0.53 to -0.25)

View on PubMed

Phytoestrogens for menopausal vasomotor symptoms (Cochrane Review)

PMID: 24323914 2013 系統性回顧 n = 4,364

Finding: No conclusive evidence that phytoestrogen supplements reduce hot flush frequency or severity overall; high-genistein extracts (>30 mg/day) consistently reduced frequency in 4 non-pooled trials; strong placebo effect in most trials (1–59% reduction).

🟢 High quality Academic Effect size: Promensil subgroup: MD -0.93 (NS); high-genistein: directionally positive, not pooled

View on PubMed

Use of Plant-Based Therapies and Menopausal Symptoms: A Systematic Review and Meta-analysis (JAMA)

PMID: 2529629 2016 統合分析 n = 6,653

— See PubMed for details

View on PubMed

Effects of soy isoflavones on menopausal symptoms in perimenopausal women: a systematic review and meta-analysis

PMID: 40718787 2025 統合分析 n = 533

Finding: Soy isoflavones effective for overall menopausal symptoms (Hedges' g = -0.25, p=0.00); however, no significant effect specifically on hot flushes in this perimenopausal cohort. Strongest effect was for depression (g = -0.72).

Effect size: Overall: Hedges' g = -0.25; hot flushes: NS

View on PubMed

The effect of soy isoflavones given to women in the climacteric period on menopausal symptoms and quality of life: Systematic review

PMID: 38825560 2024 統合分析 n = 425

Finding: No significant effect on overall menopausal symptoms (SMD -0.49, p=0.14) or QoL; significant effect only for depression (SMD -0.41, p=0.01). High risk of conflict of interest noted.

Effect size: Symptoms: SMD -0.49 (NS); Depression: SMD -0.41 (p=0.01)

View on PubMed

🏛️Regulatory & authoritative positionsL4/L5 · FDA / EMA / NIH ODS / Cochrane / Mayo …

L4a US FDA

Cautious

L4b EU EFSA

Against

L4c UK NHS

Cautious

Complementary and alternative treatments, such as herbal remedies and compounded bioidentical ("natural") hormones, are not recommended for symptoms of the menopause or perimenopause. [...] Some complementary and alternative therapies can also interact with other medicines and cause side effects. [nhs.uk/conditions/menopause/treatment/] | NICE NG23 rec.1.4.7: "Explain to people that there is so… source↗

L4d TW TFDA / 衛福部

Cautious

使用原料『大豆萃取物』之有容器或包裝食品應標示警語：「不建議兒童、少年、孕婦、哺乳期婦女、婦科腫瘤患者或有其家族病史者食用」及「異黃酮(Isoflavones)每日食用限量為50毫克以下」字樣，並應於產品容器或外包裝標示該產品依每日建議食用量之異黃酮含量。 source↗

L5b Mayo Clinic

Against

Some plants have substances that are like the hormone estrogen, such as soy, red clover and flaxseed. But studies most often have found that plant estrogens help menopause symptoms little or not at all. source↗

L5c Cleveland Clinic

Cautious

L5d Harvard Health

Cautious

L5e Specialty Society (condition-mapped)

Against

✓PMID 100% verifiedevery citation checked via NCBI Entrez

🔬7 PubMed studiesindependently re-checked by multiple sub-agents

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