A meta-analysis of more than 1 million people across the globe found that moderate drinkers all have one thing in common: They tend to live longer than nondrinkers and, especially, heavier drinkers.
"Our data shows that consumption of little amounts of alcohol leads to a reduction of mortality up to 18 percent," said lead author of the study Augusto Di Castelnuovo, a researcher at Catholic University of Campobasso, Italy. "But after a certain number of glasses things radically change. [He or she] who drinks too much not only loses this advantage, but increases his own risk of death in relation to the amount of alcohol consumed."
The research, published in the December issue of the Archives of Internal Medicine, states that the study was conducted because, although moderate alcohol consumption is associated with favorable heart health, the substance's relation to mortality is still "controversial" (possibly more so considering three to four glasses of wine a day for men is considered moderate in Europe, while four glasses is considered heavy drinking in a United States-based study).
The scientists pooled information from 34 studies from around the world--excluding Africa and South America--that examined the lifestyle factor of 1,015,835 subjects, in research that, in some cases, dated back to the early 1980s. During the two and a half decades, a total of 94,533 deaths were recorded and Di Castelnuovo and his team analysed their causes of death, be it natural or unnatural, in relation to their drinking habits.
The team found that when compared to nondrinkers, a low dose of alcohol--the equivalent of half a glass of wine--consumed every day resulted in the greatest protection for both sexes, at an average of 18 percent lower mortality.
After half a glass, the results differ between the sexes. Women who drink the equivalent of one glass of wine a day had a 16 percent lower mortality rate than nondrinkers. Women who drank two and a half glasses, though, broke even with abstainers, and anything more than that and the risk of dying became greater. Women who drank four servings of alcohol per day where 20 percent more likely to die younger, when compared to nondrinkers.
The same effect was observed in men, but at greater proportional quantities of consumption. Half a glass proved to be the most protective, but men had ten percent lower mortality at three servings (instead of two for women). At four drinks they were even with nondrinkers, and had a 20 percent greater risk of mortality with seven drinks a day.
Moderate drinking and longer life, and its different relations to women and men, was "a fact linked to metabolism," said Licia Iacoviello, head of the Genetic and Environmental Epidemiology Laboratory at the university. "We know that women metabolize alcohol in a different way and the blood-alcohol concentration reaches higher levels. Therefore, consuming more than two doses might lead to several harmful effects," she warned, "such as liver diseases or increased risk of certain forms of tumors."
However, the scientists said there are many problems with such wide-reaching estimations, and that the focus should not be on how much one should drink to prolong life, but on the way alcohol is consumed.
"It is the way we drink that makes the difference: little amounts, preferably during meals, this appears to be the right way," said coauthor Giovanni De Gaetano, the director of the research laboratories at the university. "This is another feature of the Mediterranean diet, where alcohol, wine above all, is the ideal partner of a dinner or lunch, but that's all." he said. "The rest of the day must be absolutely alcohol-free."
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