*Geek Box: Effects of Flavonoids on the Cardiovascular System
In previous Deepdives where we have focused on flavonoids and the brain, we have discussed three main mechanisms of action identified for flavonoids: stimulation of pathways associated with learning and memory; resolving inflammation; and improving cerebrovascular blood flow.
But in nutrition research there are strong common themes between what is good for the head and good for the heart. And so it is with flavonoids, as it turns out that the effects of flavonoids on vascular function and inflammation are also crucial to the cardiovascular effects of these compounds.
Let’s start with vascular function, and endothelial function in particular. The endothelium lines the insides of blood vessels, and endothelial cells release various signals to regulate blood vessel constriction/dilation, blood clotting, and immune responses. Flavonoids act by increasing expression of an enzyme called endothelial nitric oxide synthase [eNOS], which enhances vascular dilation and therefore lowers blood pressure.
Flavonoids also inhibit inflammatory pathways that influence endothelial inflammation and immune responses. One notable effect of flavonoids in relation to the inflammatory-immune effects on the vascular system is to inhibit the adhesion of monocytes, a type of white blood cell, to the endothelium during inflammatory and immune responses. There is also some evidence that flavonoids may lower the susceptibility of LDL to oxidation, which is a critical step in the development of plaque in the arteries.
However, in terms of strength of evidence it would be the vascular effects of flavonoids that are, at this point, likely to explain in part the cardiovascular benefits associated with these compounds, observed both in epidemiology and intervention studies.