All 3 studies report beneficial effects of cocoa flavanols on reducing systolic blood pressure, with effect sizes ranging from small to moderate. The most-studied dose is 500 mg twice daily, and effects have been observed over a median duration of 30 days. Evidence comes from one meta-analysis and two RCTs in older adults without cardiovascular disease.
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). The meta-analysis reported a small effect (−1.56 mmHg), while the two RCTs reported moderate reductions (−5.4 to −7 mmHg), suggesting possible overestimation in smaller trials.
catechin supplementation decreased systolic (-1.56 [-2.75, -0.37] mmHg) and diastolic blood pressure (-0.95 [-1.69, -0.20] mmHg)
the systolic blood pressure decreased by 7 mmHg [∼4.7 ± 1.9% (p = 0.04)]
CF decreased resting systolic and diastolic BP by 5.4 mmHg (95% CI -10.7 to -0.1 mmHg) and 2.9 mmHg (95% CI -5.5 to -0.4 mmHg), respectively.