Ethanol and cardiac health
Recent attention in the medical press has focussed on the reported association between “moderate” alcohol consumption and decreased risk of sudden death, especially from cardiovascular causes. This has met with angry reactions from anti-liquor campaigners culminating in an emotional and sometimes bitter controversy. The following discussion is an attempt at presenting and analysing the facts available at present in a critical, unbiased manner.
To begin with, it must be admitted indubitably that alcohol is a vasodilator. But this is not the reason for alcohol’s beneficial effects on the heart since the vasodilation is mostly confined to cutaneous vessels producing the warm, flushed skin of acute intoxication. There is virtually no increase in coronary blood flow in human beings. In fact, in individuals with existing coronary artery disease, ethanol decreases the time period of exercise required to precipitate angina and to produce changes in the ECG which are indica-tive of myocardial ischaemia. It has been proved conclusively that ethanol induces the release of catecholamines from the adrenal medulla, and while intoxicating doses can produce widespread vasodilation, moderate doses can cause appreciable vasoconstriction in such vital areas as the heart and the brain.
However, several studies in the recent past indicated a clear negative corelation between chronic ingestion of small amounts of ethanol and the incidence of coronary heart disease, beginning with the Kaiser-Permanente epidemiologic study done way back in 1974 which was at first received with scepticism by the scientific community. But it marked the beginning of a barrage of studies all around the globe over the next two decades establishing the clear association between moderate alcohol consumption and reduced risk of coronary heart disease. After much study and deliberation investigators have now come to the conclusion that the protective effect of ethanol on the heart is because it increases the concentration of high density lipoproteins (HDL) in the plasma, while at the same time decreasing that of low density lipoproteins (LDL). It is well known that the lower the concentration of HDL in the blood the greater is the risk for developing coronary heart disease (CHD). The reverse is true for LDL. Today several studies have established a convincing relationship between alcohol intake and the level of protective HDL, including both its HDL2 and HDL3 subfractions. Angiographic studies have also demonstrated that moderate alcohol consumers have less severe coronary atherosclerosis than teetotallers. Among the different types of alcoholic beverages there is evidence to suggest that wine (especially red wine) offers maximum protection.
It is now also clear that apart from its beneficial effect on cholesterol levels, alcohol has favourable effects on haemostatic factors such as plasma fibrinogen, fibrinolytic activity, and platelet adhesiveness. Investigations have demonstrated a clear-cut association between ethanol consumption and plasma levels of tissue plasminogen activator which is a major component of the fibrinolytic system. Increased fibrinolytic activity is very important in the prevention of coronary thrombosis and supplements the anti-atherosclerotic effect via the HDL-cholesterol levels. Even forensic autopsies have pointed towards a positive asociation between moderate drinking and cardiac health.
Having come to this conclusion, it must be emphasized that the purported beneficial effects rapidly evaporate as consumption is increased beyond desirable levels, and in fact the deleterious effects would then be much more than in those who don’t drink at all. So the question arises: what is “moderate” alcohol consumption ? Unfortunately the definition of moderation varies from one study to another, but the balance of evidence is that the daily consumption must not exceed 2 to 3 drinks per day. A standard drink is roughly the equivalent of 45 ml of distilled spirits (15.1 gm alcohol) or 150 ml of wine (10.8 gm alcohol), or 350 ml of beer (13.2 gm alcohol).
In the final analysis, while physicians may use their discretion in advising patients about the beneficial effects of moderate ethanol consumption, it must be emphasized that safe drinking is not a panacea for sound cardiac health.
The benefits documented thus far need further study and irrefutable confirmation.