lavonoids are a group of around 4000 plants compounds that have a common 3 ring structure. Flavonoids are bioavailable in humans and studies suggest that high intakes of flavonoids are associated with protection from certain diseases. In particular, flavonoids may reduce the risk of developing cardiovascular disease. The ability of flavonoids to protect from cardiovascular disease is thought to relate to their ability to prevent free radical formation, although some evidence suggests gene regulatory activity. Recent research has shown that antioxidants such as flavonoids are protective of cardiovascular disease because they prevent the free radical induced inhibition of nitric oxide synthase. This enzyme is required for the production of nitric oxide, which in turn causes a relaxation of circular muscle in arteries. This causes a dilation of blood vessels and a lowering of blood pressure.
The protective effects of flavonoids has been investigated with regard changes to blood pressure and arterial stiffness. In a cross-sectional study of 1898 women aged 17 to 75 years1, researchers measured the flavonoid intakes of a number of sub-groups including anthocyanins, flavan-3-ols (catechins), flavanones, flavonols, flavones and proanthocyanidins, using a food frequency questionnaire. The researchers then directly measured a number of cardiovascular parameters associated with impaired nitric oxide synthesis. The results showed that a higher intake of anthocyanins was significantly associated with a lower central systolic blood pressure as well as a lower mean arterial blood pressure. In addition, a higher flavone intake, a higher wine intake and a higher berry intake were all associated with a lower pulse wave velocity. Wine, berries, anthocyanins and flavones may all therefore be protective of cardiovascular disease.
One of the mechanisms by which flavonoids may protect from cardiovascular disease therefore may be due to the protective effects on arterial function. Atherosclerosis was originally considered to be caused by blood lipid abnormalities including increased concentrations of low density lipoprotein (LDL). However, this theory has fallen out of favour and current thinking suggests that arterial stiffness is actually caused by excessive free radical generation and underproduction of nitric oxide. The anthocyanins in berries appear to be particularly protective of the endothelial lining of arteries. This may relate to their specific properties with regard absorption and metabolism. Anthocyanins are unique amongst the flavonoids because they are absorbed intact from the stomach and flavonoid glycosides are therefore present in plasma following ingestion.
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