It's the time of the office party. Up and down the country, the festive season is well and truly under way, as colleagues pour out of the work place and into the works do for the annual end-of-year piss-up. But as the first couple of pints/glasses of wine turn into a handful, and the hours and conversations blur, what exactly is happening inside your body? And how bad for you is it?
Perhaps it isn't bad at all. Maybe we should follow the example of the French government, which is considering reclassifying wine as a "natural food" rather than an alcoholic drink. It is not the first time the French have challenged conventional thinking on alcohol. The discovery of the so-called French paradox - that levels of coronary heart disease are low in the country despite high amounts of dietary fat - triggered much of the recent research into the possible health benefits of drinking red wine. Several decades on, study after study has shown the same thing: drinking can be good for you, whether it be wine, beer or spirits. "We have known for some time that moderate consumption of alcohol might protect against coronary heart disease," says Charmaine Griffiths, spokesperson for the British Heart Foundation.
The word "moderate" is key. And that is not the only caveat. One of the reasons that there seem to be so many contrary or confusing stories about alcohol and health in the media is that the story cannot be told in such simple terms. Moderate drinking is not good for "health" per se; it protects against a very specific condition caused when fatty deposits build up in the arteries. There is evidence that it also protects against diabetes, gall stones and one form of stroke, called ischaemic stroke. Yet the same alcohol raises your blood pressure and probably increases your chances of contracting cancer of the oesophagus. Certainly, health experts are not yet ready to advise teetotallers to hit the bottle.
Exactly how moderate drinking helps fight heart disease is still a mystery. This is down to the nature of the research that suggested the link in the first place. Called epidemiology, this type of study follows large groups of people over several years to match their behaviour with what happens to them. There is evidence from more than 20 countries that moderate drinkers have 20-40% less incidence of coronary heart disease than non-drinkers. One problem with such epidemiological trials is that they are what statisticians call confounding. People who drink less are likely to be more health-conscious all round, so they probably have better diets and take more exercise, which lowers their risk of heart disease. At the other extreme, ill people do not drink - the sick quitters' hypothesis - possibly skewing the results towards suggesting that those who do are more healthy.
After years of controversy, most experts agree that these confounding effects can be worked through, and that the effect is genuine. But this association between drinking habits and better health casts no light on how one actually causes the other.
Scientists' best guess is that alcohol brings changes in blood cholesterol, which comes in two main forms, known as high and low density lipoproteins (HDL and LDL). Crudely, LDL, high levels of which are associated with a greater risk of heart disease, is bad; HDL cholesterol seems to protect the arteries and is good. Alcohol raises levels of HDL cholesterol.
Does it matter what you drink? Some studies have suggested that red wine is best, because it's full of tannins and other chemicals, from the polyphenol family, that slow down blood clotting and help to widen constricted coronary arteries. Others say this effect would be small and that the ethanol (the chief alcoholic ingredient in all booze) is key. "As of today we don't have any evidence that beverage type matters, at least with the main mechanisms of HDL and cholesterol," says Ken Mukamal, an expert on alcohol and health at Harvard University. Some of this uncertainty could come from similar social factors to those that confound the epidemiologists' work. Wine drinkers may be better educated than beer guzzlers and take better care of themselves.
But before you crack open the bottle, let's find out what happens when we drink booze. First stop is the stomach. Contrary to popular belief, very little alcohol is absorbed there. That is the job of the small intestine, but first the drink has to reach it, and that means passing through something called the pyloric valve, which links the two. The quicker this little ring of muscle opens, the quicker alcohol passes into the blood and you feel the effects. Sugars and fats keep it closed, hence creamy and sugary drinks release their hit more slowly than a slug of vodka - the origin for the drinkers' tale that a glass of milk lines your stomach.
Once alcohol is swirling through the bloodstream the focus switches to the brain. Already a complicated mess of signals and pathways, alcohol makes the situation worse as the chemical lights up various regions, closes down others and generally makes a nuisance of itself. First to be affected are receptors in areas associated with thinking, remembering and pleasure seeking, which are activated more readily. Alpha brainwaves increase, a sign of relaxation, and blood flow to frontal areas associated with mood increases. In short, you feel great.
But if that was the up, get ready for the down. Push past about three or four drinks and the previously pleasurably over-activated receptors start to seize up; other sedative pathways come online to stop neurons firing. Another couple of tequila slammers and, studies suggest, blood flow slows to regions that process sensory, motor and coordination information. And, as a final insult, the alcohol seems to make glucose metabolism in the sozzled brain drop sharply - perhaps explaining everything from blurred vision to slurred chat-up lines. In short, you're a mess.
And that's not the worst of it. The following morning, in the shape of a thirst-raging, stomach-churning, head-banging hell, comes the hangover. Dehydration is the main cause: alcohol suppresses a hormone that stops urine being excreted. During our repeated trips to the loo, we pee more water than we drink. The body then borrows water from organs including the brain, which shrink. The time-honoured glass of water before bed helps address this devastating dehydration, but offers no protection from other hangover effects.
Persistent heavy drinking (roughly defined as more than five or six tipples a day) attacks the liver. It is not alcohol that does the damage, but toxic free-radicals and other substances released as the body struggles to break it down. This means that a third of those who drink heavily develop the serious inflammatory condition alcoholic hepatitis, and a fifth get the fatal build-up of scar tissue in the liver, a sign of cirrhosis.
Exactly what makes some people and not others develop the liver condition is unclear - most individuals who drink heavily for a few weeks will have fatty deposits accumulate in their livers, which disappear if they stick to soft drinks for a while. But continued heavy drinking can bring on sudden inflammation, scarring and the onset of cirrhosis. There are no nerves to signal pain in the liver; sufferers have no idea of the damage they are causing themselves until it is at a very late stage.
Weekend binge drinking - a peculiarly British habit - also has its risks. According to George Davey Smith, of the University of Bristol, there is increasing evidence that binge drinking can interfere with the sensitive electrical rhythms needed to keep the heart muscles beating, with tragic results. "Binge drinking seems to be associated with just dropping dead," Davey Smith says. Studies in Finland and the former Soviet Union show cases of sudden death syndrome peak at the weekend, and are more common among people who say they regularly suffer from hangovers - a sure sign of bingeing behaviour.
All of which means that when you agree to that second, and then third, pint, or gradually work through an opened bottle of wine, it does not take much for the benefit to your heart to be cancelled out. For most people, the drinking never goes that far; a few blurry mornings after the office party will be the worst of their occasional excesses.
Drinkers, it seems, feel generally happier about their health than abstainers. A study in 2001 of 19,000 adults found that wine and beer drinkers were more optimistic about their health, however much they drank, which is probably enough to make anyone raise a glass. Still, as the late evolutionary biologist Stephen Jay Gould said: "We ought to be enormously suspicious of ideas that are enormously comforting."
