What does one glass of alcohol do to your body? 

Source: https://www.telegraph.co.uk/

Jack Rear

19 DECEMBER 2019 

Tis the season to be merry – but by now, all those Christmas work drinks and quick-pints-with-friends are starting to take their toll. And that’s before we mention the habitual glass of wine we use to wind down at home.

According to the NHS, the maximum you can safely drink in a week is 14 units (that’s six pints of beer or six medium glasses of wine) – but even then, the alcohol you consume is a toxin: it has an affect on your body. That’s why the health guidelines also recommend you go booze-free for a couple of days every week, to give your organs a chance to recover.

To understand what’s happening to your body after just one glass of wine – and by extension, why you start to feel so low in the drip-drip December party season – the first step is to appreciate exactly what alcohol is. The answer, in a nutshell, is a product of fermentation, when yeast tears apart sugars (in fruit, grain, potatoes, etc) and forms ethanol and carbon dioxide. Ethanol is the part of the alcohol which gets you drunk, causes you to pee more, and, in the long term, can cause liver damage and cancer.

It’s also the thing that makes you tired, happy, and unrested – after just one drink. 

What happens to your single unit of alcohol? 

So, there you are, at the bar sipping the one glass of diluted ethanol you’re allowing yourself to drink this evening, perhaps with a dilution of quinine to add to the flavour. As you sip, the ethanol pours down your throat and into your stomach, where about 20pc of it is absorbed. The other 80pc goes to the small intestine to be absorbed there. 

Small blood vessels take the absorbed alcohol molecules around your body. The liver recognises its presence and dispatches a team of enzymes which break the ethanol down in a process called metabolisation.

“When the alcohol is being broken down it goes through a number of intermediary steps in the liver before it is made harmless and disappears,” explains Dr William Alazawi consultant hepatologist at the London Digestive Centre, at The Princess Grace Hospital. The trouble is what the liver breaks ethanol down into: acetaldehyde then acetate, both poisonous substances that the body has to eject (at best, through digestion; at worst, through vomiting – although that’s very unlikely to happen after one drink).

“The rate at which the liver metabolises alcohol tends to be fairly consistent,” adds Alazawi. “It’s not the case that the more you drink the faster the liver works. The liver works at its own rate.” So just one glass puts the liver to work.

Toilet troubles 

You’ve probably heard that alcohol has a diuretic effect, but what does that really mean? Ethanol inhibits the release of a hormone called vasopressin. Ordinarily, this hormone tells the kidneys to hold onto water. Therefore, as alcohol suppresses it, the kidneys start to release more water, making you need to pee more.

In addition to suppressing vaspressin, there’s another element to alcohol causing increased toilet useage. “Alcohol is itself a diuretic,” says Dr Naveen Puri, lead physician in BUPA Health Clinics. “So it just promotes diuresis or the desire to go for a wee.”

So after just one drink, you’re hit with a triple-whammy of bladder bloat. There’s the need to excrete the liquid you just consumed, the diuretic effect of the alcohol, and the suppression of vasopressin causing the kidneys to release about 10pc more water than normal.

Brain changes

“Broadly speaking there are excitatory neurotransmitters – things that stimulate the brain – and there are inhibitory neurotransmitters – ones that decrease brain activity,” says Puri. “Alcohol has an effect on both of those.

“It makes you think less clearly because it affects the cerebral cortex; that’s the centre responsible for thought processing and also consciousness. That centre also has the inhibitory part of the brain: if you have alcohol, it will reduce inhibitions and therefore you will do things that you wouldn’t necessarily do normally.” 

But that’s not all alcohol does to your brain. It also affects the cerebellum, the area of the brain concerned with movement and balance. And the medulla, which is responsible for breathing regulation, loss of consciousness and temperature control. And it suppresses glutamate, the excitatory neurotransmitter which stimulates waking and alertness. Hence why you feel sluggish after just one drink.

Finally, there’s the old pleasure hormone, dopamine. “Alcohol has the effect of giving you a small hit of dopamine, so that’s why it’s pleasurable relatively speaking compared to say, drinking water,” says Puri.

Restless sleep 

When you wake up after a big night of drinking, you feel worn out and tired, like you barely slept. But what you might not realise is the same thing can happen when you have just one drink – only on a smaller scale.

“There are these ‘distractors’, things that cause us to go into stress mode, and alcohol is a significant one,” explains FirstBeat sports scientist Nigel Stockill. “The body detects alcohol and sees it as a toxin, so it focuses all its resources on detoxifying that alcohol.” He says the body neglects the “fluffy stuff”, such as the slowing down of heart rhythm, which happens when we’re relaxed and during restorative sleep.

“When we talk about every unit of alcohol taking a minimum of an hour to detoxify, it’s only after that the body can even begin to relax and recover,” says Stockill. “Having as little as one unit of alcohol in your system at bedtime can delay the onset of restorative sleep by around one hour. Have just two large glasses of wine (approximately 6 units) late in the evening and sleep for six hours and you may not get any restorative sleep, and therefore won’t recover overnight.”

How does the body get rid of alcohol? 

Eventually, the liver breaks ethanol down into carbon dioxide and water, which you release through breathing, sweating and peeing. As Stockill mentions, the rule of thumb is that it takes about an hour per unit. 

However, many factors can influence how quickly alcohol is metabolised such as age, race, body size, so it’s not always a straight conversion. “I wouldn’t rely on that rule of thumb,” warns Alazawi. “I think it’s really important to underscore the fact that you shouldn’t drink and drive at all. Your judgement may well be impaired after even just one drink.”

However, “the liver is generally good at regenerating itself so a minor amount of injury can be regenerated without any problems,” adds Alazawi. One glass, consumed a good couple of hours before bedtime, is probably fine for you; it’s when you start drinking more than the liver can process that you start damaging it, potentially causing scar tissue to start appearing.

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