Dietary flavonoids: effects on endothelial function and blood pressure

Several population studies have found an inverse association between flavonoid intake and risk of cardiovascular disease. These studies have resulted in the hypothesis that dietary flavonoids protect against cardiovascular disease. Many in vitro studies, studies using animal models and human intervention trials have been carried out to investigate how flavonoids might provide protection. Emerging and largely consistent evidence suggests that flavonoids can improve endothelial function and may reduce blood pressure. In vitro studies show that a variety of flavonoids cause vasorelaxation of isolated arteries from rats. In human intervention trials, flavonoids derived from tea and cocoa or dark chocolate - both rich sources of catechins - have been found to improve endothelial function acutely and with regular ingestion. The evidence for benefits of flavonoids from other dietary sources is less clear. Improvements in endothelial function could contribute to lower blood pressure. Population studies have associated higher intake of tea and chocolate with lower blood pressure. Short-term intervention studies in humans have shown blood pressure lowering with cocoa or dark chocolate, but short-term regular ingestion of tea has not been found to lower blood pressure. The long-term effects of regular ingestion of a flavonoid-enriched diet on endothelial function and blood pressure have yet to be assessed. In addition, there is evidence that flavonoid metabolism is an important factor influencing the biological activity and effects of dietary flavonoids, but further studies are needed to investigate this area. (c) 2006 Society of Chemical Industry