Dietary flavonoid intake and cardiovascular mortality.

In this issue of the British Journal of Nutrition, Mursu et al. have reported the association between flavonoid intake, cardiovascular mortality and ischaemic stroke among a group of participants in the Kuopio Ischaemic Heart Disease Risk Factor Study. After following up 1950 Finnish men for an average time of 15·2 years, they ascertained 102 ischaemic strokes and 153 CVD deaths. They found no significant association between total flavonoid intake and risk of ischaemic stroke and cardiovascular mortality; however, individual subclasses of flavonoids were marginally associated with reduced risk of ischaemic stroke and CVD mortality; those in the highest quartile of flavonol intakes had lower risks for ischaemic stroke and those in the highest quartile of flavanone and flavone intakes were less likely to die of CVD. Fruit and vegetable intakes have consistently been reported to be inversely associated with cardiovascular mortality. Parts of this association might be explained by their higher content of flavonoids. Several epidemiological studies have assessed the association between flavonoid intakes and cardiovascular risk, albeit with inconsistent results. Overall, available data suggest that those with higher intakes of flavonoids have modestly lower risks for CVD. However, very few studies considered all flavonoid subclasses and most have used dietary intakes of one or two subclasses. The study by Mursu et al. is the second that has used updated US Department of Agriculture databases of flavonoids. Investigators from the Iowa Women’s Health Study, using updated US Department of Agriculture data, found no significant association between total flavonoid intake and CHD mortality. However, most investigators believe that flavonoids can affect cardiovascular health due to their powerful antioxidant activities. Several reports have shown that flavonoids might reduce LDL-cholesterol susceptibility to oxidation. Because considerable evidence indicates that increased oxidative damage may contribute to the development of CVD, it is logical to expect cardioprotective effects of flavonoids. The potential anti-inflammatory effects, improvement in endothelial function and inhibition of platelet aggregation have also been suggested as other cardioprotective mechanisms of flavonoids.