What is alcohol? | New Scientist

Alcohol is a psychoactive drug that has been consumed in drinks for most of human history. In chemistry, the term alcohol refers to a whole class of organic compounds that include a hydroxyl group – consisting of an oxygen atom and a hydrogen atom – bonded to a carbon atom. In common parlance, however, the word alcohol usually refers to a specific chemical with the formula C2H5OH, which chemists call ethanol.

Alcohol is produced naturally when yeasts ferment sugars to generate energy, and some animals that eat a lot of fruit or nectar have evolved to metabolise it. Chemical evidence from fragments of pottery in China suggests that humans began brewing alcoholic drinks at least 9000 years ago.

Although Homer Simpson’s description of alcohol as “the cause of, and solution to, all of life’s problems” may not be entirely accurate, it encapsulates the drug’s ability to make people feel either very good or very bad. The individual involved, the amount of alcohol consumed and the social context all play a role in determining what effects it can have.

What effect does alcohol have on the body?

After you drink alcohol, it is absorbed into the blood, where it can travel to the brain. At low levels, alcohol typically makes people feel relaxed, animated and disinhibited. It can also impair coordination and judgement, which is why it is considered unsafe to drive after drinking alcohol.

At higher concentrations, the effects of alcohol become more severe, and people find it harder to think clearly. They may be more prone to losing control of their emotions and becoming aggressive, which is why alcohol is sometimes a factor in violent crime and antisocial behaviour. A very high blood alcohol level can cause people to pass out and potentially stop breathing.

Alcohol also affects the regulation of body fluids, causing people to urinate more and become dehydrated.

If someone drinks excessively, they often feel unwell the following day – a condition called a hangover. Hangovers can involve a wide range of symptoms, including headache, dry mouth, tiredness, nausea and low mood. Alcohol also impairs memory, so people may struggle to remember what happened while they were drunk.

In the long term, high levels of alcohol consumption can cause health problems and increase the risk of many diseases, including several types of cancer, dementia, heart and liver disease as well as affecting mental health. According to the World Health Organization, 3 million deaths worldwide are attributable to alcohol each year. Some users develop alcohol addiction, called alcoholism. Drinking alcohol while pregnant can cause developmental disorders in the fetus.

Is drinking alcohol bad for you?

The UK’s official guidance changed in 2016 to say that both men and women should drink no more than 14 units of alcohol a week, equivalent to about six pints of average-strength beer or 10 small glasses of low-strength wine. Some studies have claimed that having one or two drinks a day is linked to better health than avoiding alcohol completely. However, it is hard to unpick correlation and causation in these studies, and the putative benefits of moderate drinking remain controversial.

Alcohol can exert such a wide range of effects because it interacts with numerous receptors on brain cells. One of its major mechanisms is to mimic the action of GABA, an inhibitory neurotransmitter in the brain, bringing about sedative effects. It also inhibits the activity of glutamate, an excitatory neurotransmitter. In addition, alcohol activates the reward system of the brain, triggering the release of dopamine and serotonin, which makes low doses feel enjoyable.

Drinking behaviour is strongly influenced by both biological and social factors, explaining why some people choose to avoid it, some enjoy moderate amounts and others have difficulty stopping. Recent findings show that FGF21, a hormone produced by the liver, accounts for some individual differences in our response to alcohol.

Even a temporary break from alcohol consumption, be it a month, as promoted by the Dry January campaign, or just introducing alcohol-free days, can have health benefits, such as lowering high blood pressure, cholesterol and diabetes risk.