The Role of Polyphenols in Cardiovascular Diseases

Diet rich in fruits and vegetables has been associated with a decreased risk of cardiovascular diseases (CVD). Polyphenols, such as flavonoids and phenolic acids, are ubiquitous in plants and thus potential protective compounds in them. Several epidemiological studies have suggested a high intake of dietary flavonoids to be associated with a decreased risk of coronary heart disease, but the studies on stroke are limited. In addition, out of tens of potentially health beneficial polyphenols, studies have concentrated on a few. The most popular hypothesis for the protective mechanism(s) is the ability of polyphenols to act as antioxidants, but the studies have resulted in inconsistent findings. The aims of this work were to study the relation between dietary polyphenol intake and carotid atherosclerosis, and risk of CVD. In addition, our aim was to explore possible mechanisms of action by studying the effects of polyphenol supplementation on oxidative stress in humans. In the first study, the association between flavonoid intake and atherosclerosis, assessed with the common carotid artery intima-media thickness (CCA-IMT), was explored in 1380 middle-aged men participating in the Kuopio Ischaemic Heart Disease Risk Factor (KIHD) study. In this crosssectional study, the high intake of flavonoids was associated with a decreased CCA-IMT. In a consequent follow-up study, we studied the relation between flavonoid intake and the risk of ischemic stroke and CVD death in 1950 middle-aged men of the KIHD study. In this study, the high intake of flavonoids, especially flavonols, was associated with a decreased risk of ischemic stroke. In a three week supplementation trial, we studied the effects of chocolate polyphenols on serum lipids and lipid peroxidation in 45 healthy, nonsmoking volunteers. We found that chocolate polyphenols increased the concentration of serum high-density lipoprotein (HDL) cholesterol in a dose dependent manner, but had no effect on lipid peroxidation. We also assessed the effects of three week consumption of coffee (0, 450 or 900 ml/d), which is rich source of phenolic acids, on lipid peroxidation in 45 healthy, nonsmoking men. In this study, no effect of coffee on lipid peroxidation was observed. In a four week double blind supplementation study, we assessed the effects of catechin rich phloem on serum lipids and lipid peroxidation in 75 nonsmoking, hyperlipidemic, but otherwise healthy men. In the study phloem decreased lipid peroxidation, measured as oxidation susceptibility of whole serum, while no changes in other the parameters were observed. In summary, these results suggest that the high intake of dietary flavonoids may be associated with decreased carotid atherosclerosis and the risk of ischemic stroke. We found little support for the hypothesis that flavonoids and other polyphenols would decrease lipid peroxidation in humans. National Library of Medical Classification: QU 85, QU 95, QU 220, QV 223, QV 325, QZ 180, WB 438, WG 120, WL 355 Medical Subject Headings: Antioxidants; Cacao; Coffee; Cardiovascular Diseases/prevention and control; Cerebrovascular Accident/prevention and control; Cholesterol, HDL; Diet; Double-Blind Method; Finland; Flavonoids; Fruit; Heart Diseases/prevention and control; Lipid Peroxidation; Male; Middle Aged; Oxidative Stress; Phenols; Phloem; Plant Bark; Risk Factors; Vegetables