Impact of cocoa flavanols on blood pressure and vascular function: an updated systematic review and meta-analysis of randomized controlled trials

Background and objective While elevated blood pressure is a major cardiovascular risk factor, a comprehensive evaluation of not only blood pressure but also vascular function is essential to evaluate the risk of cardiovascular diseases and the effectiveness of interventions. Cocoa flavanols may lower blood pressure by improving endothelial function, however evidence regarding vascular indices is limited, and findings remain inconsistent and not the latest. We conducted an updated systematic review and meta-analysis to comprehensively evaluate the effects of cocoa flavanol intake on blood pressure and vascular function. Methods This review was registered in UMIN-CTR (UMIN000059995), and we searched PubMed, Cochrane Library, Ichushi-Web, JDreamIII, ICTRP and UMIN-CTR for eligible randomized controlled trials up to December 8, 2025. Primary outcomes were systolic and diastolic blood pressure (SBP/DBP); secondary outcomes were flow-mediated dilation (FMD), pulse wave velocity (PWV), and ankle–brachial index (ABI). Mean differences (MD) with 95% confidence intervals (CIs) were pooled using a random-effects model. Risk of bias was assessed using a modified version of the Cochrane Risk of Bias 2 (RoB 2), and certainty of evidence was graded. Results Twenty-five studies (n = 1,167) included hypertensive and normotensive participants; daily cocoa flavanol doses ranged from 10.6 to 1,680 mg. Both SBP and DBP decreased significantly following cocoa flavanol intake (SBP: MD −2.734 mmHg, 95% CI [−3.446, −2.023]; DBP: MD −1.848 mmHg, 95% CI [−2.725, −0.971]). Significant improvements were also observed for FMD (MD 1.314%, 95% CI [1.043, 1.585]) and PWV (MD −0.200 m/s, 95% CI [−0.393, −0.007]), whereas ABI showed no significant change, with limited evidence from only two studies. Subgroup analyses were consistent for SBP/DBP in both hypertensive and normotensive participants. Dose–response analyses revealed a significant inverse association between SBP or DBP and flavanol intake, but did not identify clear dose thresholds within the examined intake range. Certainty was moderate for SBP; other outcomes were limited. Conclusion These findings suggest that cocoa flavanol intake of 10.6–1,680 mg/day may modestly reduce blood pressure and may improve selected vascular function indices, although certainty for vascular outcomes remains limited.