Flavonoids, flavonoid-rich foods, and cardiovascular risk: a meta-analysis of randomized controlled trials

• Published in: The American journal of clinical nutrition 2008-07, Vol.88 (1), p.38-50
• Main Authors: Hooper, Lee, Kroon, Paul A, Rimm, Eric B, Cohn, Jeffrey S, Harvey, Ian, Le Cornu, Kathryn A, Ryder, Jonathan J, Hall, Wendy L, Cassidy, Aedín
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; blood lipids; blood pressure; Blood Pressure - drug effects; Cacao - chemistry; cardioprotective effect; Cardiovascular disease; cardiovascular diseases; Cardiovascular Diseases - blood; Cardiovascular Diseases - epidemiology; chocolate; Clinical trials; Diet; Effects; Endothelium, Vascular - drug effects; Feeding. Feeding behavior; flavonoid-rich foods; flavonoids; Flavonoids - pharmacology; flow-mediated dilatation; Fundamental and applied biological sciences. Psychology; human nutrition; Humans; Lipid Metabolism - drug effects; lipoproteins; Meta-analysis; Mortality; protein isolates; randomized clinical trials; Randomized Controlled Trials as Topic; Risk Factors; soy protein; Soybean Proteins - pharmacology; Tea - chemistry; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vitis - chemistry
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/88.1.38

BACKGROUND:The beneficial effects of flavonoid consumption on cardiovascular risk are supported by mechanistic and epidemiologic evidence. OBJECTIVE:We aimed to systematically review the effectiveness of different flavonoid subclasses and flavonoid-rich food sources on cardiovascular disease (CVD) and risk factors--ie, lipoproteins, blood pressure, and flow-mediated dilatation (FMD). DESIGN:Methods included a structured search strategy on MEDLINE, EMBASE, and Cochrane databases; formal inclusion or exclusion, data extraction, and validity assessment; and meta-analysis. RESULTS:One hundred thirty-three trials were included. No randomized controlled trial studied effects on CVD morbidity or mortality. Significant heterogeneity confirmed differential effects between flavonoid subclasses and foods. Chocolate increased FMD after acute (3.99%; 95% CI: 2.86, 5.12; 6 studies) and chronic (1.45%; 0.62, 2.28; 2 studies) intake and reduced systolic (-5.88 mm Hg; -9.55, -2.21; 5 studies) and diastolic (-3.30 mm Hg; -5.77, -0.83; 4 studies) blood pressure. Soy protein isolate (but not other soy products or components) significantly reduced diastolic blood pressure (-1.99 mm Hg; -2.86, -1.12; 9 studies) and LDL cholesterol (-0.19 mmol/L; -0.24, -0.14; 39 studies). Acute black tea consumption increased systolic (5.69 mm Hg; 1.52, 9.86; 4 studies) and diastolic (2.56 mm Hg; 1.03, 4.10; 4 studies) blood pressure. Green tea reduced LDL (-0.23 mmol/L; -0.34, -0.12; 4 studies). For many of the other flavonoids, there was insufficient evidence to draw conclusions about efficacy. CONCLUSIONS:To date, the effects of flavonoids from soy and cocoa have been the main focus of attention. Future studies should focus on other commonly consumed subclasses (eg, anthocyanins and flavanones), examine dose-response effects, and be of long enough duration to allow assessment of clinically relevant endpoints.