"Recent papers strongly indicate that its effect is significant, and in a range of undoubted public health value," says Professor de Gaetano, speaking at a Symposium on "the bitter-sweet relationship" between the gourmand and his heart (read the ESC Congress Report here
). A meta-analysis conducted by his group of pooled data from 13 studies involving 209,418 subjects found a relative risk of vascular disease associated with wine intake of 0.68 (95% CI, 0.59-0.77) relative to non-drinkers. This statistically significant inverse association was found up to a daily intake of 150 mL of wine.
However, a second arm of the same analysis with respect to moderate beer consumption, derived from 15 studies involving 208,036 subjects, found a less impressive relative risk of 0.78 (95% CI, 0.70-0.86). Unlike wine, no significant relationship between different amounts of beer intake and vascular risk was found after meta-analyzing seven studies involving 136,382 subjects. Any conclusions about beer, says Professor de Gaetano, are thus more difficult to draw.
Despite the weight of epidemiological evidence about moderate wine consumption, there are still doubts about the validity of the studies, with some suggesting that "moderate" wine drinkers will be more healthy, educated subjects and thus more likely to bring a self-selecting bias into any observational study. Studies controlling for such confounders have still found protective results, but there are inconsistencies. Studies into excessive drinking, however, show no such protective effect. A July report in the Journal of Clinical Endocrinology and Metabolism showed that Americans drinking beyond the US recommendation of two (men) or one (women) alcoholic drink per day are at an increased risk of the metabolic syndrome.
The mechanisms underlying the apparently beneficial effects of wine have been mainly limited to lipid metabolism, haemostasis and the specific antioxidant and vasorelaxant properties of its polyphenolic constituents. The latter are the recurring explanations for the beneficial effects of dark chocolate and green tea on endothelial function, both of which have been studied by the Athens group of Dr Charalambos Vlachopoulos (who in tomorrow's Symposium will be speaking on coffee!).
A study reported in the June issue of the ESC's European Journal of Cardiovascular Prevention and Rehabilitation from Dr Vlachopoulos's group found that flow-mediated dilatation of the brachial artery increased significantly following the consumption of green tea, reaching a peak of 3.9% just 30 minutes after consumption. No such increase was found in subjects who consumed a caffeine drink or hot water.
While black tea has been associated with improved short and long-term endothelial performance, this was the first study to show green tea's short-term beneficial effect on the large arteries. Other studies have already shown that green tea reverses endothelial dysfunction in smokers.
Green tea, which originates in China but is now consumed throughout the world, is made with pure leaves, and has undergone little oxidisation during processing. The cardiovascular benefits of all teas - as well as dark chocolate and red wine - are attributed to the flavonoids they contain and their antioxidant activity. However, says Dr Vlachopoulos, flavonoids in green tea are probably more potent antioxidants than in black tea because there has been no oxidisation.