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Head-to-head evidence comparison — which supplement is right for you?
Cocoa Flavanols vs Iron: Iron has the stronger overall evidence (9 vs 5/10); they're alternatives for sharpen focus — the best pick depends on your goals. Take the 60-second quiz for a pick tailored to your goals.
Iron wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Too few graded studies
0 of 1 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
6 of 8 studies with measurable effects showed benefit.
Top outcomes
200-500 mg cocoa flavanols daily (COSMOS used 500 mg a day). A cited dose-response meta-analysis put the peak endothelial benefit near 710 mg, above the highest dose in the cited trials.
Any time of day
Standardized cocoa flavanol extract (epicatechin-standardized)
18-40mg elemental iron for deficiency (varies by severity) (a typical label dose, not the dose used in the cited trials, which used 60 to 120 mg a day)
On empty stomach if tolerated, Away from tea, coffee, dairy
Ferrous bisglycinate (gentle, well-absorbed) or iron protein succinylate
and 6 more not shown
2-8 weeks
Acute to 8 weeks
Years
Throughout use
2-4 weeks
4-8 weeks
4-12 weeks
Effect of cocoa flavanol supplementation for the prevention of cardiovascular disease events: the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial.
Am J Clin Nutr (2022) · Rct · n=21442
21,442 older US adults, 500mg flavanols/day, median 3.6 years, double-blind placebo-controlled
Effect of cocoa on blood pressure.
Cochrane Database Syst Rev (2017) · Meta analysis
Cochrane meta-analysis of flavanol-rich cocoa vs control
Dose-response relationship between cocoa flavanols and human endothelial function: a systematic review and meta-analysis of randomized trials.
Food Funct (2019) · Meta analysis
15 articles, 18 intervention arms pooled
Daily oral iron supplementation during pregnancy
The Cochrane database of systematic reviews (2024) · Meta analysis · n=48971
There is probably little to no difference in maternal death (2 versus 4 events, RR 0.57, 95% CI 0.12 to 2.69; 3 trials, 14,060 women; moderate-certainty evidence).
The Prevalence of Anemia among Pregnant Women in China: A Systematic Review and Meta-Analysis
Nutrients (2024) · Meta analysis · n=1376204
The results showed that the prevalence of anemia, ID, and IDA among pregnant women in China were 30.7% (95% CI: 26.6%, 34.7%), 45.6% (95% CI: 37.0%, 54.2%), and 17.3% (95% CI: 13.9%, 20.7%), respectively.
Treatment for women with postpartum iron deficiency anaemia
The Cochrane database of systematic reviews (2024) · Meta analysis · n=4558
Intravenous iron versus oral iron supplementation The evidence is very uncertain about the effect of intravenous iron on mortality (risk ratio (RR) 2.95, 95% confidence interval (CI) 0.12 to 71.96; P = 0.51; I² = not applicable; 3 RCTs; 1 event; 572 women; very low-certainty evidence).
Iron has a higher evidence score (9/10 vs 5/10) and wins in 2 of 3 categories.
For sharpen focus, Cocoa Flavanols has a higher relevance score (28 vs 20).
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.