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Head-to-head evidence comparison — which supplement is right for you?
Calcium wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
18 of 20 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
13 of 15 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (3)
Outcomes where both Calcium and Red Clover have evidence — compare verdict strength side-by-side.
1000–1200mg daily (split doses)
Split doses with meals, 500mg with breakfast, 500mg with dinner
Calcium Citrate
40-80mg isoflavones daily
With meals, Consistent daily timing
Standardized extract (40mg isoflavones per dose)
Combined red clover isoflavones and calcium supplementation shows superior preservation of bone mineral density compared to calcium alone in postmenopausal women, where declining estrogen impairs calcium retention.
Red clover isoflavones (40–80 mg/day) combined with calcium (1000–1200 mg/day) and vitamin D3 provides a useful non-hormonal bone protection strategy in perimenopausal and postmenopausal women.
6-24 months
12-36 months
Throughout pregnancy
Within days of starting
4-12 weeks
6-12 months
8-12 weeks
Ongoing
Effects of combined calcium and vitamin D supplementation on osteoporosis in postmenopausal women: a systematic review and meta-analysis of randomized controlled trials.
Food & Function (2020) · Meta analysis · n=12000
Combined calcium and vitamin D significantly improved lumbar spine BMD in postmenopausal women
Association Between Calcium or Vitamin D Supplementation and Fracture Incidence in Community-Dwelling Older Adults: A Systematic Review and Meta-analysis.
JAMA (2017) · Meta analysis · n=51145
33 trials involving 51,145 participants were analyzed
Vitamin D and Calcium for the Prevention of Fracture: A Systematic Review and Meta-analysis.
JAMA Network Open (2019) · Meta analysis · n=51419
Meta-analysis of 11 randomized clinical trials with 51,419 participants
The effectiveness of nutritional supplements in improving polycystic ovary syndrome in women: a systematic review and network meta-analysis
Reproductive biology and endocrinology : RB&E (2025) · Meta analysis · n=5501
Inositol significantly decreased total cholesterol and triglyceride levels, while curcumin was most effective in improving low-density and high-density lipoprotein cholesterol levels.
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
The effect of soy protein on the lipid profile showed a significant decrease in TC levels: WMD = -0.15; 95% CI: -0.25-0.05; p = 0.0048, LDL-C levels: WMD = -0.15; 95% CI: -0.25-0.05; p = 0.0067, as well as a significant increase in HDL-C levels: WMD = 0.05; 95% CI: 0.02-0.08; p = 0.0034.
Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies
Reproductive toxicology (Elmsford, N.Y.) (2021) · Meta analysis · n=752
Sub-analysis of the data according to isoflavone dose and study duration also showed no effect.
Based on meta-analysis of 59 RCTs showing 0.6-1.8% BMD increases. Requires vitamin D co-supplementation for optimal effect. Effectiveness plateaus beyond 1200mg daily.
Based on meta-analysis showing statistically moderate reduction in daily hot flash frequency. Effect size is modest and individual response varies significantly.
AI-estimated from published studies. Interpret as directional guidance.
Calcium has a higher evidence score (8/10 vs 7.5/10) and wins in 2 of 3 categories.
For bone health, Calcium has a higher relevance score (95 vs 72).
Calcium and Red Clover may work well together: Combined red clover isoflavones and calcium supplementation shows superior preservation of bone mineral density compared to calcium alone in postmenopausal women, where declining estrogen impairs calcium retention. Red clover isoflavones (40–80 mg/day) combined with calcium (1000–1200 mg/day) and vitamin D3 provides a useful non-hormonal bone protection strategy in perimenopausal and postmenopausal women.