Several studies have indicated that moderate drinkers have a lower risk of both nonfatal myocardial infarction and fatal heart disease than do abstainers. To determine whether alcohol truly prevents coronary heart disease or whether other factors may contribute to this observed relationship, researchers conducted a systematic literature review and a combined analysis (i.e., meta-analysis) of 42 published studies. This analysis found that consumption of up to two drinks per day can promote changes in the levels of molecules that reduce the risk of heart disease while also increasing the levels of certain molecules that promote heart disease. Alcohol also may affect the risk of heart disease by acting on other various other molecules involved in a variety of physiological processes related to heart disease. Finally, the relationship between alcohol consumption and heart disease may be modulated by genetic factors.