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Head-to-head evidence comparison — which supplement is right for you?
Soy Isoflavones vs Vitamin K2: Soy Isoflavones has the stronger overall evidence (6 vs 6/10); they're alternatives for menopause support — the best pick depends on your goals. Take the 60-second quiz for a pick tailored to your goals.
Soy Isoflavones wins 1 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
9 of 11 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
10 of 13 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (2)
Outcomes where both Soy Isoflavones and Vitamin K2 have evidence — compare verdict strength side-by-side.
40-80mg isoflavones daily
Divided doses with meals, Consistent daily timing
Standardized soy isoflavone extract
100-200mcg (MK-7)
With a meal containing fat
MK-7 (menaquinone-7)
and 1 more not shown
4-12 weeks
6-12 months
8-12 weeks
Initial use
6-12 months
1-3 years
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).
Vitamins K2 and D3 Improve Long COVID, Fungal Translocation, and Inflammation: Randomized Controlled Trial
Nutrients (2025) · Rct · n=151
The median age was 46 years; 71% were female and 29% were non-white.
The effect of vitamin K2 supplementation on bone turnover biochemical markers in postmenopausal osteoporosis patients: a systematic review and meta-analysis
Frontiers in endocrinology (2025) · Meta analysis · n=2570
Vitamin K2 (VK2) increased osteocalcin (OC; MD 1.86, 95% CI 1.17-2.56) and bone-specific alkaline phosphatase (BAP; MD 1.49, 95% CI 0.98-2.00).
Vitamin K2 in Managing Nocturnal Leg Cramps: A Randomized Clinical Trial
JAMA internal medicine (2024) · Rct · n=310
Of the 199 enrolled individuals, 108 (54.3%) were female, and the mean (SD) age was 72.3 (5.5) years.
Meta-analysis of 533 participants showed effectiveness for menopausal symptoms. Effect size appears modest and heterogeneity was noted across studies. Individual response varies significantly.
Based on meta-analyses showing 2.17% WMD improvement in lumbar BMD. Effects primarily demonstrated with MK-7 form in postmenopausal women. Combination with vitamin D3 may enhance effects.
AI-estimated from published studies. Interpret as directional guidance.
Soy Isoflavones has a higher evidence score (6/10 vs 6/10) and wins in 1 of 3 categories.
For menopause support, Soy Isoflavones has a higher relevance score (90 vs 80).
No known interactions between Soy Isoflavones and Vitamin K2 have been documented in our database. However, always consult a healthcare provider before combining supplements.
Hot flashes, bone, sleep, muscle — the basics that hold up vs the phytoestrogen hype.
The transition years (40s): cycle changes, mood, sleep, brain fog — foundations, vitex, and starting muscle work early.
Which supplements clash with blood thinners, thyroid meds, antibiotics & more — and what to do.
Worth it if you’re deficient (and many are) — dosing, testing, D3 vs D2, and the K2 question.
The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.