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Si9.0
Soy Isoflavones Research
Likely helpsModerate safety
36 peer-reviewed studies
What the evidence says
Likely helps
Soy Isoflavones appears to help in 8 of 10 studies with measurable effects — the evidence leans clearly favourable.
Most evidence is from high-quality meta-analyses and randomised trials published 2004–2026 with a typical study size of 789 participants.
Based on 36 studies · 29 meta-analyses · 2 RCTs · 29,637 total participants
Confidence
High
What the studies found
8helped2unclear· 26 more without graded effect data
By outcome
Women's healthMay help manage menopausal symptoms like hot flashes and mood changes · 4-8 weeks · Supports healthy estrogen metabolism and hormonal equilibrium · 4-8 weeks · May help reduce menstrual discomfort and PMS symptoms · 1-3 cycles
Likely helps35 studies
Cholesterol & lipids
Probably helps13 studies
Glucose & metabolic
Mostly mechanism / observational8 studies
Heart & blood pressure
Mostly mechanism / observational6 studies
InflammationImproved lipid profile · 8-12 weeks
Mostly mechanism / observational5 studies
Bone healthSupports bone mineral density and skeletal strength · 8-12 weeks
Mostly mechanism / observational4 studies
Therapeutic & clinical
Mostly mechanism / observational4 studies
Cognitive function
Mostly mechanism / observational3 studies
Weight management
Mostly mechanism / observational3 studies
Liver health
Too few graded studies2 studies
Depression & moodReduced hot flashes and menopausal symptoms · 4-12 weeks
Too few graded studies1 study
Safety profile
Too few graded studies1 study
By the numbers
Pulled from 27 studies with measurable effects
Likely real effects
86%
across studies
People studied
30k
typical study: 789 people
Strongest designs
31
29 pooled, 2 randomised
Showed benefit
80%
8/10 studies
How long studies ran
1–3 months
1
Populations Studied
Postmenopausal women5
Menopausal women5
Women with polycystic ovary syndrome1
Perimenopausal women1
Active research area
25 studies in the last 5 years · Latest meta-analysis: 2025
200420152026
1PCOS symptoms improvementMeta-AnalysisCited 2×n=5,501 · very large study2025
Chromium, inositol, and Omega-3 were found to be beneficial for improving lipid profile.
Zhao G et al. · Reproductive biology and endocrinology : RB&E (2025)
Inositol significantly decreased total cholesterol and triglyceride levels, while curcumin was most effective in improving low-density and high-density lipoprotein cholesterol levels.
Chromium, inositol, and Omega-3 were found to be beneficial for improving lipid profile.
For improving obesity, sex hormone levels, inflammatory factors and oxidative stress indicators of PCOS patients, carnitine, chromium, and soy isoflavones are effective options, respectively.
2Measures of estrogenicityMeta-AnalysisCited 7×n=3,285 · very large study2025
Addressing public health concerns may promote soy foods as high-quality plant protein sources with low environmental impact and cost, particularly benefiting postmenopausal women and aligning with ...
Viscardi G et al. · Advances in nutrition (Bethesda, Md.) (2025)
Addressing public health concerns may promote soy foods as high-quality plant protein sources with low environmental impact and cost, particularly benefiting postmenopausal women and aligning with sustainable dietary patterns and guidelines.
This study was registered in PROSPERO as CRD42023439239.
3Systematic ReviewCited 16×n=3,254 · very large study2025
There is some evidence to support the use of nutritional interventions for improving psychological symptoms of PMS.
Robinson J et al. · Nutrition reviews (2025)
There is some evidence to support the use of nutritional interventions for improving psychological symptoms of PMS.
However, more research using consistent protocols, procedures to minimize risk of bias, intention-to-treat analysis, and clearer reporting is required to provide conclusive nutritional recommendations for improving PMS-related psychological outcomes.
4Menopausal symptomsMeta-AnalysisCited 3×n=533 · large study2025
More trials should be conducted in the future to validate our findings.
Luan H et al. · PeerJ (2025)
Noticeable benefit
← WorseNo effectBetter →
Likely real
In October 2024, we screened 2,099 articles, of which 12 were eligible for meta-analysis, and found that soy isoflavones were effective for treating menopausal symptoms (seven studies, 533 participants, Hedges' g = -0.25, 95% CI [-0.42 to -0.08], p = 0.00).
However, our results should be interpreted with caution owing to the small sample size.
More trials should be conducted in the future to validate our findings.
5Non-alcoholic fatty liver disease parametersMeta-AnalysisCited 64×n=2,173 · very large study2022
Based on current evidence, curcumin can reduce BMI, TG, TC, liver enzymes, and insulin resistance; catechin can reduce BMI, insulin resistance, and TG effectively; silymarin can reduce liver enzymes.
Yang K et al. · Frontiers in immunology (2022)
Based on current evidence, curcumin can reduce BMI, TG, TC, liver enzymes, and insulin resistance; catechin can reduce BMI, insulin resistance, and TG effectively; silymarin can reduce liver enzymes.
For resveratrol, naringenin, anthocyanin, hesperidin, and catechin, more RCTs are needed to further evaluate their efficacy and safety.
7Fasting blood glucoseMeta-AnalysisCited 35×n=1,529 · large study2016
Although the results displayed a significant tendency in favor of soy isoflavones, it appears that genistein alone played an important role in improving glucose metabolism due to its low heterogeneity.
Fang K et al. · Molecular nutrition & food research (2016)
Noticeable benefit
← WorseNo effectBetter →
The overall results showed that the average difference in fasting blood glucose values between women assigned to soy isoflavones and women in placebo groups was -0.22 mmol/L (95% CI: -0.38 to -0.07 mmol/L) under a random-effects model.
In addition, the effect of soy isoflavones on insulin was also significant: -0.43 μIU/mL (95% CI: -0.71 to -0.14 μIU/mL), as was the effect on homeostasis model assessment insulin resistance (HOMA-IR): -0.52 (95% CI: -0.76 to -0.28).
Although the results displayed a significant tendency in favor of soy isoflavones, it appears that genistein alone played an important role in improving glucose metabolism due to its low heterogeneity.
9Bone mineral densityMeta-AnalysisCited 11×n=63 · small study2024
This systematic review and meta-analysis suggests that isoflavone interventions, especially those containing genistein of at least 50 mg/day, can effectively enhance BMD in postmenopausal women.
Inpan R et al. · Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA (2024)
This systematic review and meta-analysis suggests that isoflavone interventions, especially those containing genistein of at least 50 mg/day, can effectively enhance BMD in postmenopausal women.
10Tumor area in hormone-dependent cancersMeta-AnalysisCited 5×n=30 · small study2024
Therefore, caution should be exercised when considering the intake of dietary isoflavones in female hormone-dependent cancer patients, particularly in the form of supplements.
Chakravarti B et al. · Phytotherapy research : PTR (2024)
Huge benefit
← WorseNo effectBetter →
Likely real
On the other hand, dietary isoflavones increased tumor area (Hedge's g = 1.136, 95% CI = 0.752 to 1.520, p = 0.000).
Dietary isoflavones have potential benefits and risks in female hormone-dependent cancers.
Therefore, caution should be exercised when considering the intake of dietary isoflavones in female hormone-dependent cancer patients, particularly in the form of supplements.
Although our results clearly showed soy isoflavones containing soy protein can have decreasing effect on inflammation in participants with chronic inflammatory disease, more large-scale and high quality interventional studies still need to be done to clarify our results.
Gholami A et al. · Journal of health, population, and nutrition (2025)
Noticeable benefit
← WorseNo effectBetter →
Likely real
Twenty-seven articles were involved in the systematic review and twenty-two articles with thirty-four effect sizes were considered for meta-analysis.
The overall estimates revealed that soy isoflavones containing soy protein significantly decreased serum levels of CRP in comparison with control group (weighted mean difference (WMD)= -0.49 mg/L; 95% confidence interval (CI): -0.74, -0.25; P = 0 < 0.001).
Although our results clearly showed soy isoflavones containing soy protein can have decreasing effect on inflammation in participants with chronic inflammatory disease, more large-scale and high quality interventional studies still need to be done to clarify our results.
12Serum concentration of leptinMeta-Analysisn=421 · medium study2022
Soy isoflavones plus soy protein had a non-significant decreasing effect on the serum concentration of leptin.
Gholami A et al. · Clinical nutrition ESPEN (2022)
No clear effect
← WorseNo effectBetter →
A pooled analysis revealed that the combination of soy isoflavones and soy protein had a borderline non-significant on serum concentration of leptin (weighted mean difference (WMD): -1.03 ng/ml, 95% confidence interval (CI): -2.11, 0.05 ng/ml).
Soy isoflavones plus soy protein had a non-significant decreasing effect on the serum concentration of leptin.
However, making firm conclusion needs more studies on participants with different health condition, and different soy isoflavones doses and intervention duration.
Still, the inconsistent results across the included RCTs require further clinical research to establish optimal dosage and duration.
Ranneh Y et al. · Nutrients (2024)
Most studies on silymarin showed a reduction in liver enzymes and lipid profile; however, no changes were observed in inflammatory cytokine levels.
The dietary supplementation of hesperidin and naringenin or green tea extract caused improvements in liver enzyme, lipid profile, and inflammatory cytokine, while genistein supplementation did not modulate blood lipid profile.
In conclusion, dietary supplementation of polyphenols could potentially prevent and ameliorate NAFLD.
14Cancer-specific mortality and recurrenceMeta-AnalysisCited 15×2024
Soy, enterolactone, and green tea demonstrated significant risk reductions in outcomes following breast cancer.
van Die MD et al. · JNCI cancer spectrum (2024)
Large benefit
← WorseNo effectBetter →
Soy protein and products were inversely associated with cancer-specific mortality for estrogen receptor-positive disease (HR = 0.75, 95% CI = 0.60 to 0.92).
An inverse association was observed for serum or plasma enterolactone, measured prediagnosis and early postdiagnosis, with cancer-specific mortality (HR = 0.72, 95% CI = 0.58 to 0.90) and all-cause mortality (HR = 0.69, 95% CI = 0.57 to 0.83).
There was a 44% reduced risk of recurrence with prediagnostic green tea for stage I and II breast cancer (HR = 0.56, 95% CI = 0.38 to 0.83).
15Menopausal symptoms and quality of lifeMeta-AnalysisCited 5×2024
According to the results of the analysis, soy isoflavones had no effect on menopausal symptoms (vasomotor, psychosocial, physical, sexual, and urogenital complaints) and quality of life in climacteric women but did reduce the level of depression.
Gençtürk N et al. · Explore (New York, N.Y.) (2024)
According to the results of the analysis, soy isoflavones had no effect on menopausal symptoms (vasomotor, psychosocial, physical, sexual, and urogenital complaints) and quality of life in climacteric women but did reduce the level of depression.
There was a high risk of conflict of interest in the included studies.
16Clinical outcomes in diabetic nephropathyMeta-AnalysisCited 6×2024
Moderate to low amounts of evidence suggest that supplementation with probiotics, vitamin D, soy isoflavones, coenzyme Q10, dietary polyphenols, antioxidant vitamins, or salt-restricted diets may significantly improve clinical outcomes in patients with DN.
Cai L et al. · Frontiers in endocrinology (2024)
Moderate-quality evidence suggested that probiotic supplementation could significantly improve blood urea nitrogen (BUN), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels in DN patients.
Low-quality evidence indicated that probiotic supplementation significantly improved the serum creatinine concentration, urinary albumin-creatinine ratio (UACR), fasting blood glucose (FBG), HbA1c and high-density lipoprotein cholesterol (HDL-C) in DN patients.
In addition, low-quality evidence suggested that a salt restriction diet could significantly improve the creatinine clearance rate (CrCl) in patients with DN.
Our results suggests that soy and its isoflavones can be effective in correction changes in lipid metabolism in postmenopausal women and may favorably influence in preventing cardiovascular events.
Barańska A et al. · Nutrients (2021)
Subgroup analysis and meta-regression were performed to assess the modifiers of treatment response.
In total, in the analysis studies, 2305 postmenopausal women took part.
Our results suggests that soy and its isoflavones can be effective in correction changes in lipid metabolism in postmenopausal women and may favorably influence in preventing cardiovascular events.
18Hot flashes and menopausal symptomsMeta-AnalysisCited 166×n=62 · small study2016
This meta-analysis of clinical trials suggests that composite and specific phytoestrogen supplementations were associated with modest reductions in the frequency of hot flashes and vaginal dryness but no significant reduction in night sweats.
Franco OH et al. · JAMA (2016)
There was substantial heterogeneity in quality across the available studies, and 46 (74%) of the included randomized clinical trials demonstrated a high risk of bias within 3 or more areas of study quality.
This meta-analysis of clinical trials suggests that composite and specific phytoestrogen supplementations were associated with modest reductions in the frequency of hot flashes and vaginal dryness but no significant reduction in night sweats.
However, because of general suboptimal quality and the heterogeneous nature of the current evidence, further rigorous studies are needed to determine the association of plant-based and natural therapies with menopausal health.
20IL-6 and TNF-α concentrationsMeta-AnalysisCited 6×2022
In conclusion, our meta-analysis did not confirm any significant effect on serum concentration of IL-6 and TNF-α among post-menopausal women.
Gholami A et al. · Clinical and experimental pharmacology & physiology (2022)
The mean change from baseline and its standard deviation (SD) for intervention and comparison groups were used to calculate the effect size.
In subgroup analysis, soy isoflavones plus soy protein could increase the serum concentration of IL-6 in studies with soy isoflavones dose ≤87 mg/days, cross-over design, weak quality, and studies on participants who had health risk factors or diseases.
The serum concentration of TNF-α increased in studies with cross-over design, intervention duration ≤56 days, and body mass index (BMI) >27, and in studies that were conducted on at-risk or sick participants.