Effects of chocolate, cocoa, and flavan-3-ols on cardiovascular health: A systematic review and meta-analysis of randomized trials

Norwich Medical School, University of East Anglia, Norwich, United Kingdom.
American Journal of Clinical Nutrition (Impact Factor: 6.77). 03/2012; 95(3):740-51. DOI: 10.3945/ajcn.111.023457
Source: PubMed


There is substantial interest in chocolate and flavan-3-ols for the prevention of cardiovascular disease (CVD).
The objective was to systematically review the effects of chocolate, cocoa, and flavan-3-ols on major CVD risk factors.
We searched Medline, EMBASE, and Cochrane databases for randomized controlled trials (RCTs) of chocolate, cocoa, or flavan-3-ols. We contacted authors for additional data and conducted duplicate assessment of study inclusion, data extraction, validity, and random-effects meta-analyses.
We included 42 acute or short-term chronic (≤18 wk) RCTs that comprised 1297 participants. Insulin resistance (HOMA-IR: -0.67; 95% CI: -0.98, -0.36) was improved by chocolate or cocoa due to significant reductions in serum insulin. Flow-mediated dilatation (FMD) improved after chronic (1.34%; 95% CI: 1.00%, 1.68%) and acute (3.19%; 95% CI: 2.04%, 4.33%) intakes. Effects on HOMA-IR and FMD remained stable to sensitivity analyses. We observed reductions in diastolic blood pressure (BP; -1.60 mm Hg; 95% CI: -2.77, -0.43 mm Hg) and mean arterial pressure (-1.64 mm Hg; 95% CI: -3.27, -0.01 mm Hg) and marginally significant effects on LDL (-0.07 mmol/L; 95% CI: -0.13, 0.00 mmol/L) and HDL (0.03 mmol/L; 95% CI: 0.00, 0.06 mmol/L) cholesterol. Chocolate or cocoa improved FMD regardless of the dose consumed, whereas doses >50 mg epicatechin/d resulted in greater effects on systolic and diastolic BP. GRADE (Grading of Recommendations, Assessment, Development and Evaluation, a tool to assess quality of evidence and strength of recommendations) suggested low- to moderate-quality evidence of beneficial effects, with no suggestion of negative effects. The strength of evidence was lowered due to unclear reporting for allocation concealment, dropouts, missing data on outcomes, and heterogeneity in biomarker results in some studies.
We found consistent acute and chronic benefits of chocolate or cocoa on FMD and previously unreported promising effects on insulin and HOMA-IR. Larger, longer-duration, and independently funded trials are required to confirm the potential cardiovascular benefits of cocoa flavan-3-ols.

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Available from: Jeffrey S Cohn, Jun 25, 2014
    • "Nevertheless, in one study, consumption of a flavanol rich cocoa drink (150 mL twice a day, approximately 900 mg of flavanols) for 2 weeks improves endothelial function in patients with hypertension without changing BP or insulin sensitivity[71]. Overall, a systematic review and meta-analysis of acute and short-term randomized controlled trials[63,64]have confirmed that the consumption of flavanol rich cocoa could have beneficial effects upon BP, lipid profile, endothelial function and insulin resistance. Altogether, these evidences support the notion that cocoa could be useful in pathological situations such as metabolic syndrome and diabetes slowing the progression of DMT2 and its associated cardiovascular complications. "
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    • "In this study, cocoa extract exhibited antioxidant activity, antihyperlipidemic and membrane stabilizing effect. The T. cacao extract may exert its protective effect by radical scavenging amongst other mechanisms; as intervention studies have suggested that cocoa has several beneficial effects on cardiovascular health, which includes the lowering of blood pressure, the improvement of vascular function and glucose metabolism, the reduction of platelet aggregation and adhesion (Sudano et al., 2012a) Cocoa and its flavanols increase nitric oxide (NO) bioavailability, activate nitric oxide synthase (NOS), and exert antioxidative, anti-inflammatory, and anti-platelet effects, which in turn improves vascular function, reduces blood pressure and therefore, explains the positive impact on clinical outcome proposed by epidemiological studies (Corti et al., 2009; Shrime et al., 2011; Hooper et al., 2012; Sudano et al., 2012b). More so, there is some evidence that flavanols and flavanol-rich foods including cocoa inhibit angiotensin-converting enzyme (ACE) activity in vitro (Actis-Goretta et al., 2003; Actis- Goretta et al., 2006). "
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