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Head-to-head evidence comparison — which supplement is right for you?
Red Clover vs Vitamin D3: Vitamin D3 has the stronger overall evidence (7.5 vs 4.5/10); they're alternatives for bone health — the best pick depends on your goals. Take the 60-second quiz for a pick tailored to your goals.
Vitamin D3 wins 3 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Too few graded studies
1 of 2 studies with measurable effects showed benefit.
Top outcomes
Verdict
Probably helps
7 of 14 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (2)
Outcomes where both Red Clover and Vitamin D3 have evidence — compare verdict strength side-by-side.
40-80mg isoflavones daily
With meals, Consistent daily timing
Standardized extract (40mg isoflavones per dose)
2000-4000 IU daily
Morning with breakfast
D3 (cholecalciferol) softgel or liquid
and 1 more not shown
4-12 weeks
6-12 months
8-12 weeks
Ongoing
4-8 weeks
4-8 weeks
2-4 weeks
4-8 weeks
Role of Phytoestrogen-Rich Bioactive Substances (Linum usitatissimum L., Glycine max L., Trifolium pratense L.) in Cardiovascular Disease Prevention in Postmenopausal Women: A Systematic Review and Meta-Analysis
Nutrients (2022) · Meta analysis
Meta-analysis of flaxseed, soy and red clover trials in postmenopausal women. Each plant was pooled separately.
Evaluation of Clinical Meaningfulness of Red Clover (Trifolium pratense L.) Extract to Relieve Hot Flushes and Menopausal Symptoms in Peri- and Post-Menopausal Women: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
Nutrients (2021) · Meta analysis
Meta-analysis of eight randomised placebo-controlled trials (ten comparisons) of red clover isoflavones in peri- and postmenopausal women.
Isoflavone Supplements for Menopausal Women: A Systematic Review
Nutrients (2019) · Systematic review
We found that isoflavones reduce hot flashes even accounting for placebo effect, attenuate lumbar spine bone mineral density (BMD) loss, show beneficial effects on systolic blood pressure during early menopause, and improve glycemic control in vitro.
Vitamin D supplementation vs. placebo and incident type 2 diabetes in an ancillary study of the randomized Vitamin D and Omega-3 Trial
Nature communications (2025) · Rct · n=22220
Ancillary analysis of VITAL: 22,220 adults without T2D randomized to vitamin D3 2000 IU/day or placebo, with a meta-analysis of 3 additional trials.
Vitamin D Supplementation for Patients with Dysmenorrhoea: A Meta-Analysis with Trial Sequential Analysis of Randomised Controlled Trials
Nutrients (2024) · Meta analysis · n=687
TSA revealed that the current RCTs provide sufficient information.
Vitamin D and respiratory tract infections
BMJ (2017) · Meta analysis · n=11321
25 RCTs, 11 321 participants aged 0 to 95 years. Vitamin D reduced acute respiratory tract infection overall (adjusted OR 0.88, 95% CI 0.81 to 0.96).
The trials behind this curve used 40 to 82 mg of isoflavones a day. A meta-analysis of five trials at that range found a marginal fall of 1.5 hot flushes a day (PMID 17239573). A second meta-analysis of eight trials found a larger effect in the subgroup taking 80 mg or more (PMID 33920485), and a meta-analysis of Promensil at 80 mg found 3.6 fewer hot flushes a day (PMID 28160855). A 6-month RCT at 80 mg improved Menopause Rating Scale scores (PMID 39254422). No cited trial reports 40 mg on its own or tested more than about 80 mg, so no threshold, optimal dose or safety ceiling is plotted.
Both points come from a meta-analysis of double-blind cholecalciferol trials in people aged 60 and over (PMID 15886381). Trials at 700 to 800 IU a day cut hip fracture risk by 26% (RR 0.74) and non-vertebral fractures by 23%, plotted at 800 IU. Trials at 400 IU a day showed no benefit (hip fracture RR 1.15), and the WHI trial of 400 IU with 1,000 mg calcium did not significantly reduce hip fracture (PMID 16481635). Most of these trials also gave calcium, and the Cochrane review found vitamin D alone unlikely to prevent fractures while vitamin D with calcium gave a small reduction (PMID 24729336). Doses above 800 IU were not compared, so no optimal dose or ceiling is set.
AI-estimated from published studies. Interpret as directional guidance.
Vitamin D3 has a higher evidence score (7.5/10 vs 4.5/10) and wins in 3 of 3 categories.
For bone health, Vitamin D3 has a higher relevance score (92 vs 60).
No documented interaction was found in the data searched. This does not establish that this exact combination is safe.
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The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.