Berries are protective of cardiovascular disease, possibly because of the flavonoids that give them their blue and red colours. Although the mechanisms by which flavonoids provide vascular protection is unknown, epidemiological and clinical evidence continues to accumulate to show their benefits. Some of the cardioprotective effects reported from consumption of flavonoid rich foods include reduced blood pressure, decreased platelet aggregation, reversal of insulin resistance and anti-inflammatory effects. In addition, very recent research has shown that flavonoids may be able to reverse endothelial dysfunction, a key mechanism in the development of cardiovascular disease. Endothelial dysfunction is characterised by a decrease in endothelium derived relaxing factor (nitric oxide) and induction of inflammation that together increase arterial stiffness and promote arthrosclerosis. Preliminary evidence suggests that cranberry juice may be able to improve the acute condition of some parameters of arterial stiffness in subjects with cardiovascular disease.
For example, researchers1 have investigated the effects of cranberry juice consumption on measurements of arterial stiffness and vascular function in 44 subjects with coronary artery disease. In a cross-over design study, subjects consumed cranberry juice containing 835mg of total polyphenols and 94mg anthocyanins for 4 weeks, followed by a 2 week rest period and then 4 weeks of a placebo beverage. Subjects were also requested to refrain from consuming other flavonoid containing foods. The results showed that the mean carotid-femoral pulse wave velocity decreased after cranberry juice consumption, but increased after the placebo period. Pulse wave velocity is a recognised measure of arterial stiffness, suggesting that the cranberry juice in the short-term, was able to reduce the stiffness seen in the arteries of the subjects. In an uncontrolled pilot study, the authors also reported an improvement in brachial artery flow-mediated dilation and digital pulse amplitude tonometry ratio.
Cranberry juice contains a number of flavonoid compounds, and is particularly rich in anthocyanins. While cranberry juice was used in this study it is tempting to speculate that similar effects could be seen with other berries that contain similar levels of flavonoid compounds. Carotid-femoral pulse wave velocity is an important measure of vascular stiffness and the ability of cranberry juice to reduce this parameter is of great interest. The fact that cranberry juice did not change measures of endothelial function suggest that perhaps cranberry juice can alter the sympathetic tone of the vasculature. The flavonoids in green and black tea are also able to reduce pulse wave velocity, as are isoflavones. Although not true flavonoids, isoflavones have similar phenolic structures to those found in tea and berries. The results from this study are therefore consistent with other studies showing vascular benefits for flavonoid compounds on measures of arterial stiffness.
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