The federal agency said that no randomized trials have been carried out in this area.
"Given their limitations, nonrandomized studies about the health effects of moderate drinking should be interpreted with caution, particularly since excessive alcohol consumption is a leading health hazard in the United States," wrote the researchers.
CDC reached its conclusion after researchers, led by Timothy Naimi of the CDC's emerging investigations and analytic methods branch, studied data gathered from the 2003 Behavioral Risk Factor Surveillance System, a telephone survey of adults in the United States.
Their aim was to determine the prevalence of 30 CVD-associated risk factors or groups of factors in the population, and potential confounders among non-drinkers and moderate drinkers (defined as male consumers of two drinks or less per day by men and women consumers of one or less).
The results of the survey, published in the May issue of the American Journal of Preventative Medicine, showed that non-drinkers were likely to be affected by 27 of the 30 risk factors, including demographic, social, behavioral, health-care access and health related factors.
The additional risk factors could therefore explain increased CDC mortality rate amongst non-drinkers group compared with moderate drinkers. The apparent protective effect of moderate alcohol consumption on CVD may be due to residual or unmeasured confounding, argued the researchers.
Amongst the studies which seem to point towards health benefits of consuming moderate amounts of alcohol is a 14-year study which investigated potential factors leading to stroke.
Between 1986 and 2000, 38,156 male participants answered questions about their diet, medical history and including alcohol consumption every four years.
"In this study, the participants who were at lowest risk for stroke were the men who consumed one or two drinks on three to four days of the week," said lead author Kenneth Mukamal, at Beth Israel Deaconess Medical Center and assistant professor of Medicine at Harvard Medical School.
However scientists at the University of Buffalo concurred with the CDC to some degree. A study published in December 2004 indicated that drinking any amount of alcohol without food could be a significant risk factor in developing high blood pressure.CDC statistics show that there 19,928 alcohol-induced deaths in the US 2002, excluding accidents and homicides, and 27,257 from chronic liver disease and cirrhosis.
According to the American Heart Association, 70.1 million Americans suffered from some form of CVD in 2002 (34,2 percent of the population), and it was the cause of 0.9 million deaths.