Abstract
The oxidation of low density lipoprotein (LDL) is one mechanism by which serum cholesterol may deposit in the arterial wall causing coronary heart disease (CHD). Epidemiological studies have provided evidence to suggest an inverse relationship between the dietary intake of flavonoids and the risk of CHD. Of the many groups of flavonoids present in foods, chiefly in vegetables, fruit, tea and wine, the polyphenols are especially important since they have been shown to express potent antioxidant activities in vitro. They are particularly abundant in red wine, a high consumption of which has been implicated in the low mortality from CHD in countries such as France, giving rise to the ‘French paradox’. Despite intense interest in the potential health benefits of dietary polyphenols, the outcome of studies addressing this issue have been largely inconclusive. The overall aim of this study was to determine whether the putatively protective effects of red wine are mediated through an in vivo antioxidant action of extracted red wine polyphenols and related foods and whether alcohol affects their biological activity. The initial objective of this study was to develop methods for assessing the oxidative status of plasma and oxidative susceptibility of LDL. Once established, these assays were used to test a range of different polyphenols for their antioxidant potential in vitro for a human ‘intervention trial’. The selected polyphenol supplements were then used as dietary supplements in a 2 week dietary intervention in healthy male volunteers. Measures of oxidation status and polyphenol content in plasma and LDL were determined before and after dietary supplementation. Supplementation with red wine and extracted red wine polyphenols either alone or in combination with white wine, alcohol, or vitamin E was associated with a significant increase in total antioxidant status of plasma and decrease in the oxidative susceptibility of LDL and lipid peroxides. It was also shown to increase the polyphenol content of plasma and LDL, and total plasma TGF-β levels. From these data it can be concluded that the polyphenols contained within red wine and similar beverages are powerful inhibitors of LDL oxidation and that alcohol promotes pro-oxidation changes in these parameters.