The Bible advises us to take a little wine for our stomachs' sakes. Scientific research confirms the spirit if not the letter of the advice. As Arthur Klatsky has just summarised authoritatively in Scientific American, drinking little and often can be good for your heart. Unfortunately, this prescription will not suit non-drinkers who are predisposed to developing an unhealthy fondness for drink.
The abuse of alcohol causes enormous misery in Ireland, and it might be argued that more good would result from advocating abstinence than from encouraging moderate drinking. But this would be to ignore the benefits to many of a little of what they fancy. The solution would seem to be that physicians can safely advise people who are at risk of developing coronary heart disease, and who have a very low risk of developing an alcohol problem, to drink alcohol in moderation.
But what does in moderation mean? The consensus is that, on average, two standard drinks a day is the upper limit of moderate drinking for men and that one standard drink a day is the limit for women. A standard drink is a glass of beer, a glass of wine or a half measure of spirits. The benefits to the heart increase as the amount consumed rises from zero to two standard drinks a day. On average, drinking more than this a day can harm overall health. It should also be noted that studies have shown a beneficial effect on coronary-heart-disease risk from consuming far less alcohol than two drinks a day - even as low as three drinks a week.
Coronary heart disease is a very serious health issue in developed countries, where it is responsible for a quarter of all deaths. It results from an accumulation of fatty deposits in arteries that route blood to the heart; the condition is technically called arteriosclerosis. It takes many years to develop, but eventually it can seriously restrict blood flow to the heart and lead to the formation of clots that block the blood vessels entirely. Restricting blood flow to the heart can cause the chest pain of angina, and severe restriction or blocking of an artery can cause fatal heart attack.
The connection between alcohol and arteriosclerosis was first hinted at in the early part of the 20th century, when pathologists noted that the large arteries of alcoholics who died from liver damage, or cirrhosis, were strikingly free of fatty deposits. Careful studies in the 1960s to discover new risk factors for coronary heart disease found, surprisingly, that abstaining from alcohol correlated with a higher risk of heart attack. Much work since then has confirmed this correlation, and the rule of thumb now is that one or two standard drinks a day reduce the risk of dying from coronary heart disease by 30 per cent, compared with not drinking at all.
Alcohol apparently protects the heart by its effect on cholesterol levels and blood clotting. Cholesterol is an important biochemical in our bodies; many of our hormones are derived from it. Our cells synthesise cholesterol, but almost 80 per cent of our cholesterol is made in our livers, and we also ingest cholesterol when we eat animal products such as meat, eggs and dairy products.
Cholesterol is transported in our bloodstream in association with special proteins called lipoproteins. Blood cholesterol is associated either with high-density lipoprotein (HDL) or low-density lipoprotein (LDL). HDL cholesterol, also known as good cholesterol, helps to protect the heart; higher levels of LDL, or bad, cholesterol are definite risk factors for heart disease. Several studies have shown that HDL cholesterol is elevated by 10 to 20 per cent in moderate drinkers; these higher levels seem to account for about half the heart-protective effect of moderate alcohol consumption. Alcohol may also interfere with the complex biochemical events involved in blood clotting, perhaps by making platelets, little blood cells that participate in clots, less sticky. This would make it more difficult for inappropriate clots to form. These occur with disastrous consequences over regions of arteriosclerosis in coronary arteries.
Wine, beer and spirits, consumed in moderate amounts, confer some protection against coronary heart disease, but is wine better than beer or spirits? Some studies have indicated that moderate wine drinkers are at 25 per cent less risk of dying from coronary heart disease than moderate beer or spirit drinkers. It is difficult to be sure about the relative merits of wine, however, as the general lifestyle habits of wine, beer and spirit drinkers tend to differ a lot. This makes it difficult to disentangle the apparent health effects of wine from other factors.
Klatsky's message is clear. All heavy drinkers should reduce consumption or abstain, as should people who are at risk from alcohol, as demonstrated, for example, by a family history of alcoholism. A select group of people are at risk of coronary heart disease, or already experiencing it, but are not at any serious risk of developing an alcohol problem. They should talk to their doctors about the pros and cons of moderate drinking as part of a heart-friendly diet.
William Reville is associate professor of biochemistry and director of electron microscopy at University College Cork