Flavonoids, which are found in many commonly consumed plant foods and beverages, improve a number of different cardiovascular risk factors, according to an article published in the July issue of the American Journal of Clinical Nutrition.

Lee Hooper, Ph.D., of the University of East Anglia in Norwich, U.K., and colleagues performed a systematic review of the literature to determine the relationship between flavonoids and cardiovascular disease (CVD), and specific CVD risk factors such as lipoproteins, blood pressure and flow-mediated dilatation. After employing a structured search strategy and applying inclusion, exclusion and validity criteria, a meta-analysis was performed.

While no randomized controlled trials examined the effects of flavonoids on CVD morbidity or mortality, 133 trials examined the effects of flavonoids on specific risk factors for CVD, the authors report. Acute and chronic chocolate intake increased flow-mediated dilatation and reduced both systolic (-5.88 mm Hg) and diastolic (-3.30 mm Hg) blood pressure. Of all soy products, only soy protein isolate significantly reduced diastolic blood pressure (-1.99 mm Hg) and low-density lipoprotein (LDL) cholesterol (-0.19 mmol/L). Black tea intake increased systolic (5.69 mm Hg) and diastolic (2.56 mm Hg) blood pressure, while green tea improved LDL (-0.23 mmol/L), the report indicates. Many flavonoids were unable to be assessed due to insufficient evidence.

"This report is the first systematic review assessing the effectiveness of the range of flavonoid subclasses and flavonoid-rich food sources on CVD risk factors within randomized controlled trials," according to the authors. But in an accompanying editorial, Johanna M. Geleijnse and Peter Hollman of Wageningen University in the Netherlands write, "Substantial evidence for a vasoprotective effect of specific flavonoids is, however, still lacking…to really advance the field, the step to individual flavonoids must be made now."

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