Soy Isoflavones
Research reviewed: Up until 03/2026
Soy Isoflavones (Soy Isoflavones (Genistein, Daidzein, Glycitein)) is a dietary supplement with 9 published peer-reviewed studies involving 2,380 participants, researched for Menopause Symptoms, Cardiovascular Health, Bone Health and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Menopause Symptoms
StrongCardiovascular Health
StrongBone Health
StrongCognitive Function
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Menopause Symptoms
To evaluate soy isoflavone supplementation on hot flush frequency and severity in postmenopausal women
Study Type
Randomised double-blind placebo-controlled trial
Purpose
To evaluate soy isoflavone supplementation on hot flush frequency and severity in postmenopausal women
Dose
150 mg soy isoflavones daily (Genistein 90 mg + Daidzein 60 mg)
Participants
197 postmenopausal women
Duration
12 weeks
Results
Soy isoflavone supplementation significantly reduced hot flush frequency (−57% vs −33% placebo) and hot flush severity. MENQOL scores improved significantly for vasomotor and psychosocial domains.
How They Measured It
Hot flush frequency (diary), hot flush severity composite score, MENQOL, serum FSH
To quantify the efficacy of soy isoflavone supplementation in reducing menopausal hot flushes
Study Type
Meta-analysis
Purpose
To quantify the efficacy of soy isoflavone supplementation in reducing menopausal hot flushes
Dose
Soy isoflavone supplements (40-160 mg/day)
Participants
Meta-analysis of 17 RCTs (n=1496)
Duration
Various
Results
Soy isoflavone supplementation significantly reduced hot flush frequency by 20.6% more than placebo. Effects were larger in Asian women and those with more frequent baseline hot flushes. Duration and dose correlated with response.
How They Measured It
Meta-analysis of hot flush frequency data from double-blind RCTs
Cardiovascular Health
To evaluate soy isoflavone supplementation on lipid profiles and cardiovascular risk in postmenopausal women
Study Type
Randomised double-blind placebo-controlled trial
Purpose
To evaluate soy isoflavone supplementation on lipid profiles and cardiovascular risk in postmenopausal women
Dose
80 mg soy isoflavones daily
Participants
350 postmenopausal women
Duration
6 months
Results
Soy isoflavones significantly reduced LDL cholesterol (−8.1%), total cholesterol (−6.3%), and CRP compared to placebo. HDL modestly increased. Effects were greatest in women with highest baseline LDL.
How They Measured It
Total cholesterol, LDL, HDL, triglycerides, CRP, fibrinogen, homocysteine
To comprehensively evaluate the cardiovascular effects of dietary soy isoflavones
Study Type
Systematic review and meta-analysis
Purpose
To comprehensively evaluate the cardiovascular effects of dietary soy isoflavones
Dose
Dietary soy protein + isoflavones or isoflavone supplements
Participants
Meta-analysis of 23 RCTs (n=1382)
Duration
Various
Results
Soy isoflavones significantly reduced LDL (−0.10 mmol/L), total cholesterol (−0.15 mmol/L), and triglycerides, while modestly increasing HDL (+0.05 mmol/L). Endothelial function (FMD) was also significantly improved.
How They Measured It
Meta-analysis of lipid, blood pressure, endothelial function from RCTs
Bone Health
To evaluate the effects of soy isoflavones on bone mineral density in postmenopausal women
Study Type
Randomised double-blind placebo-controlled trial
Purpose
To evaluate the effects of soy isoflavones on bone mineral density in postmenopausal women
Dose
80 mg soy isoflavones daily
Participants
224 postmenopausal women
Duration
3 years
Results
Soy isoflavone supplementation significantly preserved lumbar spine BMD (0.2% gain vs 0.8% loss in placebo) over 3 years. Bone resorption marker CTX was significantly lower. Equol producer subgroup showed greatest benefits.
How They Measured It
DXA scan at lumbar spine and total hip, CTX, P1NP
To determine the effects of soy isoflavones on BMD and bone turnover in postmenopausal women
Study Type
Meta-analysis
Purpose
To determine the effects of soy isoflavones on BMD and bone turnover in postmenopausal women
Dose
Soy isoflavone supplements (≥50 mg/day)
Participants
Meta-analysis of 9 RCTs (n=432)
Duration
Various
Results
Soy isoflavone supplementation significantly increased lumbar spine BMD (SMD 0.36) and reduced bone resorption markers. Effects were larger in women who were Equol producers and in the early postmenopausal period.
How They Measured It
Meta-analysis of BMD and bone turnover marker data from RCTs
Cognitive Function
To evaluate soy isoflavone supplementation on cognitive function in postmenopausal women
Study Type
Randomised double-blind placebo-controlled trial
Purpose
To evaluate soy isoflavone supplementation on cognitive function in postmenopausal women
Dose
100 mg soy isoflavones daily
Participants
202 postmenopausal women
Duration
12 months
Results
Soy isoflavone supplementation significantly improved verbal memory and category fluency compared to placebo. Greater benefits observed in women with higher baseline cognitive function and Asian ethnicity. Processing speed not affected.
How They Measured It
Neuropsychological test battery (verbal memory, attention, processing speed), serum isoflavone levels
To examine the impact of soy isoflavone supplementation on cognitive function in older men
Study Type
Randomised double-blind placebo-controlled trial
Purpose
To examine the impact of soy isoflavone supplementation on cognitive function in older men
Dose
160 mg soy isoflavones daily
Participants
122 men aged 55-74
Duration
6 months
Results
Soy isoflavone supplementation did not significantly improve cognitive outcomes in older men on the primary composite score. Secondary analyses showed modest improvements in verbal working memory in younger men (55-65 years).
How They Measured It
Neuropsychological testing (working memory, verbal/non-verbal fluency, processing speed, attention)
To evaluate the effects of soy isoflavones on cognitive function across the lifespan
Study Type
Systematic review
Purpose
To evaluate the effects of soy isoflavones on cognitive function across the lifespan
Dose
Soy isoflavone supplements and dietary soy
Participants
Meta-analysis of 12 RCTs (n=706)
Duration
Various
Results
Soy isoflavones significantly improved verbal memory (SMD 0.37) and processing speed in postmenopausal women. Effects were not significant in men or perimenopausal women. Timing of initiation relative to menopause is critical.
How They Measured It
Systematic review and meta-analysis of RCTs and observational studies
Frequently Asked Questions
Common questions about Soy Isoflavones research
There are currently 10 peer-reviewed studies on Soy Isoflavones (Soy Isoflavones (Genistein, Daidzein, Glycitein)), involving 2,380 total participants. Research covers Menopause symptoms, Cardiovascular health, Bone health and 1 more areas. The overall evidence strength is rated as Very Strong.
The evidence is currently rated as "Very Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (9 human studies), and reported outcomes.
Soy Isoflavones has been researched for: Menopause symptoms, Cardiovascular health, Bone health, Cognitive function. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 9 out of 10 studies are human trials. Human trials carry more weight in our evidence scoring system.
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