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Head-to-head evidence comparison — which supplement is right for you?
NAC vs Soy Isoflavones: NAC has the stronger overall evidence (6 vs 6/10); they're alternatives for estrogen & progesterone balance — the best pick depends on your goals. Take the 60-second quiz for a pick tailored to your goals.
NAC wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
7 of 8 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
9 of 11 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (1)
Outcomes where both NAC and Soy Isoflavones have evidence — compare verdict strength side-by-side.
600-1800mg daily
Away from food, Split into 2-3 doses
NAC capsules or powder
40-80mg isoflavones daily
Divided doses with meals, Consistent daily timing
Standardized soy isoflavone extract
and 1 more not shown
4-8 weeks
2-4 weeks
1-2 weeks
Immediate
4-12 weeks
6-12 months
8-12 weeks
Initial use
Efficacy of N-Acetylcysteine in Polycystic Ovary Syndrome: Systematic Review and Meta-Analysis
Nutrients (2025) · Meta analysis · n=2515
NAC was associated with a statistically significant increase in progesterone (SMD 0.95, 95% CI: 0.13-1.77, p = 0.02) and endometrial thickness (SMD 0.58, 95% CI: 0.10-1.06, p = 0.02) compared to the placebo and other drugs (SMD 0.71, 95% CI: 0.48-0.94, p < 0.0001).
Efficacy of N-acetylcysteine for patients with depression: An updated systematic review and meta-analysis
General hospital psychiatry (2024) · Meta analysis · n=904
Our findings indicate that adjunctive NAC can ameliorate depressive symptoms in patients with psychiatric problems, particularly bipolar disorder.
N-acetylcysteine as a treatment for substance use cravings: A meta-analysis
Addiction biology (2024) · Meta analysis · n=623
The most targeted substance in the clinical trials was alcohol (3/9; 33.3%), followed by tobacco (2/9; 22.2%) and multiple substances (2/9; 22.2%).
Soy isoflavones prevent bone resorption and loss, a systematic review and meta-analysis of randomized controlled trials
Critical reviews in food science and nutrition (2020) · Meta analysis · n=5313
Soy isoflavones prevent osteoporosis-related bone loss in any weight status or treatment duration.
Effect of Soy Isoflavones on Measures of Estrogenicity: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
Advances in nutrition (Bethesda, Md.) (2025) · Meta analysis · n=3285
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.
Effects of soy isoflavones on menopausal symptoms in perimenopausal women: a systematic review and meta-analysis
PeerJ (2025) · Meta analysis · n=533
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).
Meta-analysis showed efficacy particularly in bipolar disorder patients. Effect appears as adjunctive treatment. Individual response varies significantly.
Meta-analysis of 533 participants showed effectiveness for menopausal symptoms. Effect size appears modest and heterogeneity was noted across studies. Individual response varies significantly.
AI-estimated from published studies. Interpret as directional guidance.
NAC has a higher evidence score (6/10 vs 6/10) and wins in 2 of 3 categories.
For estrogen & progesterone balance, Soy Isoflavones has a higher relevance score (85 vs 65).
No known interactions between NAC and Soy Isoflavones have been documented in our database. However, always consult a healthcare provider before combining supplements.
Weight loss is the real treatment; vitamin E/omega-3 have some evidence, milk thistle modest, TUDCA thin.
Folate is essential; inositol + CoQ10 are the best bets — but conception evidence is limited.
Inositol (40:1), and the supporting cast for insulin resistance, cycles & fertility.
Hot flashes, bone, sleep, muscle — the basics that hold up vs the phytoestrogen hype.
The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.