Alcohol and the heart
Large observational studies have found beneficial cardiovascular effects with moderate alcohol consumption.
The effect of alcohol consumption on the cardiovascular system has been the source of much debate over the past few years. Heavy alcohol consumption is associated with detrimental effects on many of the body’s systems, as well as with an increased risk of addiction, motor vehicle accidents, trauma, violence, cancer, and suicide. However, large epidemiological studies also point to a multitude of potential beneficial effects with chronic moderate alcohol consumption – defined here as up to two standard alcoholic drinks (44 mL spirits, 148 mL wine, or 355 mL beer) per day for men and up to one drink per day for women. Observational studies have compared subjects abstaining from alcohol with subjects consuming alcohol and found differences in all-cause mortality and mortality due to cancer, stroke, and coronary artery disease. Despite some adverse effects on arrhythmogenesis and blood pressure, alcohol has been found to generally benefit vascular health and to lower the risk of coronary artery disease. Evidence regarding the effects of alcohol on the cardiovascular system indicates that moderate consumption of up to two drinks per day for men and one drink per day for women is associated with the greatest potential benefit at the lowest overall risk. However, randomised controlled trials are still needed to determine whether the observed associations result from alcohol consumption alone and whether the benefit found relates to the kind of alcoholic beverage consumed.
Heavy alcohol consumption is associated with detrimental effects on many of the body’s systems, as well as with an increased risk of addiction, motor vehicle accidents, trauma, violence, cancer, and suicide. However, large epidemiological studies also point to a multitude of beneficial effects with chronic moderate alcohol consumption. Evidence regarding the effect of surrounding moderate alcohol consumption on the cardiovascular (CV) system is well worth considering.
Definitions
Many different definitions are used in the literature for a “standard” drink and “moderate” alcohol consumption. In this article we use the Department of Health and Human Services and the US Department of Agriculture definition for a standard drink, which is 17.74 mL or 14 g of alcohol. This represents 44 mL (1.5 fl. oz.) of 80-proof spirits, 148 mL (5 fl. oz.) of wine, or 355 mL (12 fl. oz.) of beer. Moderate alcohol consumption is defined in the same guideline as up to two alcoholic drinks per day for men and up to one alcoholic drink per day for women.
Alcohol and mortality
The relationship between alcohol consumption and all-cause mortality has been found to conform to a J-shaped curve, which is attributed to a combination of the beneficial and harmful effects of chronic alcohol consumption. This was clearly demonstrated in a large meta-analysis involving the study of over 1 million subjects.[1] The greatest benefit on all-cause mortality was observed in subjects consuming 6 g of alcohol per day (approximately half a drink per day), while parity with abstainers was reached with subjects consuming around 44 g per day (approximately three drinks per day). Thereafter, higher levels of alcohol consumption were associated with an increase in all-cause mortality.
While both sexes benefitted from chronic alcohol consumption, the authors noted a gender difference with respect to degree of benefit and level of consumption. Although the observed maximum protection of alcohol was similar between the sexes (18% in women and 17% in men) the slopes of the two curves differed, as seen in Figure 1. Whereas up to three drinks per day remained protective in men, women only derived benefit if they consumed less than two drinks per day.
Multiple studies have attempted to subquantify the effect of alcohol consumption on the various modalities of death with remarkably similar results. When taken together, the risk of dying a cardiovascular death appears to conform to an inverse or L-shaped mortality curve, with apparent risk reductions even with consumption of more than two drinks per day.[2,3] The beneficial effects of increasing alcohol consumption on cardiovascular mortality seem to apply to most subtypes of cardiovascular disease, and are generalisable to the elderly and those with a lower baseline risk or type 2 diabetes.[2-4]
Unfortunately, the cardiovascular benefit of increasing alcohol consumption is offset by an increase in noncardiovascular death.[2,3] Specifically, there is a significant association between increasing alcohol consumption and risk of death from cirrhosis, trauma, and cancer (Figure 2).[2,3] Not surprisingly, alcohol-related cancers (mouth, esophagus, pharynx, larynx, and liver) increase in frequency with increasing consumption (RR 1.5 for two to three drinks per day [confidence interval (CI) 1.1–2.1 for men and 0.9–2.5 for women]; RR 2.8 [CI 2.1–3.8] in men and 3.0 [CI 1.7–5.3] for women for more than four drinks per day). Somewhat unexpectedly, there was an observed increase in breast cancer mortality for women who consumed even one drink per day (RR 1.3 [CI 1.1–2.6]). There was no observed relationship between colon cancer risk and alcohol consumption.[2]
When compared with either heavy consumption or abstinence, moderate alcohol consumption is associated with a lower risk of all-cause mortality. With increasing consumption, the risk of cardiac mortality continues to decrease, but the risk of noncardiac mortality (hemorrhagic stroke, cancer, cirrhosis, trauma) increases. The benefit of moderate alcohol consumption applies to the middle-aged and the elderly, as well as to those with diabetes. A gender difference exists, with women deriving less benefit than men at increasing levels of alcohol consumption.
