Numerous observational studies have shown that moderate alcohol drinkers have a lower incidence of cardiovascular disease (CVD) than do non-drinkers. Although most of these studies controlled for major cardiac risk factors, CVD is independently associated with other factors that could explain the benefits attributed to moderate drinking.
Data from the 2003 Behavioral Risk Factor Surveillance System, a population-based telephone survey of U.S. adults, was used to assess the prevalence of CVD risk factors and potential confounding factors among moderate drinkers and nondrinkers. Moderate drinking was defined as 2 drinks or fewer per day for men and 1 drink or fewer per day for women. After adjusting for age and gender, nondrinkers were more likely to have characteristics associated with increased CVD mortality in terms of demographic factors, social factors, behavioral factors, access to health care, and health-related conditions. Of the 30 CVD-associated factors or groups of factors that were assessed, 27 (90%) were significantly more prevalent among nondrinkers. Removing those with poor health status or a history of CVD did not change the results.
Comment: While alcohol is a known cardiac poison when consumed in high doses, most researchers and practitioners believe that moderate drinking is beneficial for the heart. All of the evidence supporting that viewpoint has come from observational studies or from controlled trials that measured intermediate endpoints such as lipid levels or platelet function, and there have been no randomized controlled trials directly assessing the effect of alcohol on heart disease. Reliance on observational studies has in the past led the scientific community to incorrect conclusions; for example, estrogen-replacement therapy was believed to prevent heart disease until randomized controlled trials found that it probably does the opposite.
The results of the present study suggest that there are fundamental differences between non-drinkers and people who drink moderate amounts of alcohol. Some of these differences, rather than alcohol consumption per se, might explain the association between alcohol consumption and heart disease. I have observed that many non-drinkers stay away from alcohol because consuming even small amounts makes them feel ill. Perhaps their higher risk of heart disease is caused not by the fact that they avoid alcohol, but by the same constitutional weakness which renders them intolerant to alcohol. If that is the case, then alcohol avoidance would be a marker, not a cause, of increased CVD risk, and persuading non-drinkers to drink alcohol would make them sicker, not healthier.
To be sure, there are some potentially cardioprotective substances in certain alcoholic beverages, such as silicon and glucose-tolerance factor in beer and polyphenols in red wine. However, these beneficial substances are also present in a wide range of healthful foods that do not contain alcohol.
Naimi TS, et al. Cardiovascular risk factors and confounders among nondrinking and moderate-drinking U.S. adults. Am J Prev Med 2005;28:369-373.
