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


METHODS
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.
Hooper
Lee
L
School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, United Kingdom. l.hooper@uea.ac.uk
Kroon
Paul A
PA
Rimm
Eric B
EB
Cohn
Jeffrey S
JS
Harvey
Ian
I
Le Cornu
Kathryn A
KA
Ryder
Jonathan J
JJ
Hall
Wendy L
WL
Cassidy
Aedín
A
D001794:Blood Pressure / Q000187:drug effects*; D002099:Cacao / Q000737:chemistry*; D002318:Cardiovascular Diseases / Q000097:blood / Q000453:epidemiology*; D004032:Diet; D004730:Endothelium, Vascular / Q000187:drug effects*; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects*; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D030262:Soybean Proteins / Q000494:pharmacology*; D013662:Tea / Q000737:chemistry; D027843:Vitis / Q000737:chemistry
D005419:Flavonoids; D030262:Soybean Proteins; D013662:Tea