How alcohol really affects your body: From the first sip to the long haul

Is drinking good for you? How does it impact your brain? And what causes a hangover?

Birds do it, when they eat berries that have fermented in the first frost. Bees do it, when they suck on tree sap. Educated fleas don’t do it, obviously – but “many kinds of monkeys”, noted Charles Darwin in The Descent of Man, “have a strong taste for … spirituous liquors”.

There is evidence that humans were brewing their own booze even before the wheel caught on, but how much do we know about how it works on our brains and bodies?

Well, quite a bit. Recent decades have seen dozens of studies validate some old sayings, debunk others, and give medical experts a much clearer understanding of how alcohol affects us and how much it is really okay to drink. Read on to find out.

The first sip

You may have noticed that the effects of your first drink kick in almost as soon as it hits your mouth, but that may be more to do with your expectations than the alcohol itself. “Most people, the first time they drink, find it horrible,” says Prof David Nutt, the chair of Drug Science, an independent UK scientific body researching drugs and alcohol.


“But, eventually, they come to associate the smell and taste of their favourite drink with the effect in the brain and the pleasure that’s coming.”

From the mouth and gullet, the liquid moves to your stomach, where about 20 per cent is absorbed through the stomach lining. The rest is absorbed once it reaches the small intestines, all of it ultimately ending up in your bloodstream. Food can act like a sponge and slow the alcohol’s absorption: if you are drinking on an empty stomach, the alcohol takes effect much faster. A few minutes after your first sip, once it gets to your bloodstream and into your brain, it starts to have an effect.

“This is what we call the rising phase, which is what most people are looking for,” says Prof Nutt. “Your blood vessels widen, which can make you start to feel a bit flushed, you start to feel a bit relaxed around the jaw and then you start to feel chilled and more sociable and convivial.

“That comes from Gaba, our main inhibitory neurotransmitter, which for most of us is turned down a bit in social situations, making us a bit anxious and tense.”

Alcohol, in other words, turns up the Gaba system, helping us to relax. This can also be accompanied by a temporary feeling of warmth and drop in body temperature. This is, essentially, the good bit: you’re half a pint or a glass of wine down, and things feel great.

The session

As you keep drinking, dopamine kicks in. This is the “seeking” hormone that is often associated with the drive to do things, rewarding us with a little feelgood spike whenever we think about it.

“This is where it gets moreish,” says Prof Nutt. “You get a little hit, you get energised, you get loud, and as the effect starts to diminish, you want more.

“Alcohol releases endorphins, which are the brain’s natural opiates – and they’re also addictive, turning off your sense of control so you drink more than you planned to.”

Alcohol affects the prefrontal cortex, which primarily governs cognitive control, impulse behaviour and the brain’s memory centre. This means that your judgment becomes impaired and movement is disrupted.

If you drink too much, your liver starts to feel the strain. “On average, the liver can only metabolise, or break down, roughly one small glass of wine or a pint of beer an hour,” says nutritionist Hannah Macey.

“When more than this is consumed, your liver becomes unable to deal with the workload so it begins to send alcohol to the heart. This leads to a fall in your blood pressure, while the newly alcohol-rich blood is now pumped to the lungs.”

This means that you exhale some of your intake, which, of course, is how Breathalyser tests work. Oh, and those increasingly frequent toilet breaks you take on a night out? Alcohol limits the brain’s production of antidiuretic hormone, instructing your kidneys to release more water, causing dehydration.

The morning after

While there is no single commonly accepted cause of hangovers, several bad things tend to happen in combination after a big night out.

“Dehydration is common,” says Macey. “But alcohol can also irritate the stomach lining, potentially causing diarrhoea, vomiting and an imbalance of electrolytes including sodium, potassium and magnesium, which the body needs to function well. Together with blood vessels in the brain expanding, this can all cause a thumping headache.”

It is not just the headache: overdoing it inhibits the liver’s normal ability to release sugar, leading to the sluggish feeling that comes with low blood sugar levels. The body also reacts to what it perceives as an imbalance in brain chemicals, and tries to correct it by reducing Gaba – which can cause what many drinkers think of as “hangxiety”. Finally, even one drink will negatively affect sleep, and having a few means you are unlikely to have had much beneficial sleep.

The fix? It is everything you know you should do, but don’t: eat before you start drinking to slow the absorption of alcohol into the blood, and drink plenty of water before, during and after drinking. In terms of food, protein is digested slowly, leaving you feeling fuller for longer, while fermented foods will feed the good gut bacteria you are about to start killing. The morning after, take an electrolyte supplement to replace what you have lost, eat anti-inflammatory foods containing omega-3 fatty acids, and get back on the fermented foods if you can face it.

For a slightly more kill-or-cure option, a cold shower might help. “Some evidence shows that elevated levels of adrenaline in the bloodstream can help with alcohol clearance,” says Macey. “Cold exposure is known to increase adrenaline and dopamine levels in a safe manner. But the evidence isn’t conclusive, and you should always do this safely.”

To put it another way, turning down the temperature of the shower the morning after one too many is fine, but a cold plunge while you’re still drunk could give you hypothermia, or worse.

The medium term

Before we get to alcohol’s long-term effects, what about those weeks and months when you are overdoing it – maybe you are under stress, fitting in with the culture at a new job, or just desperately trying to enjoy the summer? Well, the bad news is that it is probably not helping you much with any of those things.

For a start, the ill effects mentioned above can build up, leaving you overstressed, short on sleep, and with high blood pressure. Regular consumption can cause permanent dilation of blood vessels and weight gain. As well as the significant calories lurking in alcoholic drinks, there is some evidence linking moderate consumption of alcohol to the build-up of visceral fat around the waist, associated with a number of health risks, including cardiovascular disease and type 2 diabetes.

The good news is that alcohol doesn’t seem to affect your performance in the gym too much – as long as you are not specifically aiming to pack on muscle. “Where you may see an impact is with muscle protein synthesis,” says Scott Tindal, a performance nutrition coach and co-founder of Fuelin, a nutrition programme for athletes. He says that, although the greatest impact alcohol has on anyone trying to perform better “is on sleep quality and quantity, over time that will have a huge impact on health and performance”.

Over the medium term, booze can also kill off the helpful bacteria in your gut to an extent that can affect your immune system and mood, the latter enough to make you likely to drink more. “This can lead to a hindered immune response, negative gut symptoms and higher levels of stress, anxiety and depression,” says Macey. “It also plays havoc with our hormones, which can lead to increased hunger and diminished sex drive.”

The long haul

One of the better known health consequences of long-term alcohol consumption is liver disease. Although cirrhosis can take years to develop, regularly drinking over the recommended limits can damage the liver. Meanwhile, cutting down on drinking has become standard advice in lowering the risk of dementia. While alcohol doesn’t appear to directly kill brain cells, it can disrupt the growth of new ones – and also indirectly cause neurological problems that can lead to dementia.

Still, a glass of wine a day might help your longevity, right? Well, unfortunately, rumours of alcohol’s effectiveness in that area may have been exaggerated.

“For a long time, I think we’ve told ourselves alcohol is good for us, partly because we enjoy drinking it,” says Dr Sadie Boniface, head of research at the Institute of Alcohol Studies.

“But science has debunked some of the ‘health benefits’ of moderate drinking, and one thing I think people generally don’t understand is that the official drinking guidelines are for ‘low-risk’ alcohol consumption, not ‘safe’ consumption,” Dr Boniface says.

“When the drinking guidelines were developed, they did an enormous review of the evidence, and did calculations for the health risks of drinking at different levels.” The cut-off they chose for low-risk, she says, was a little below a 1 per cent lifetime risk of death from alcohol: “I think that’s higher than a lot of people would expect, and much higher than the risk of death that we would probably accept for other exposures, such as air pollution.”

It seems fairly clear that there is nothing in alcohol that is directly beneficial: resveratrol, an antioxidant often credited with health-boosting properties, is only present in minuscule amounts in red wine. “The World Health Organisation outlines its thinking quite clearly,” says Dr Inge Kersbergen, a lecturer in public health at the University of Sheffield in the UK.

“Essentially, even low amounts of alcohol consumption increase our risk of seven different types of cancer and there is no evidence that any protective effects for other diseases outweigh this increase in cancer risk,” Dr Kersbergen says.

“So, even though the health risks of light drinking are small, people shouldn’t drink alcohol to try to improve their health.”

Despite this, people who have a drink or two every week aren’t necessarily likely to experience worse health outcomes. A recent meta-analysis that considered results from 107 studies found that, compared with never drinking, low-volume drinking is not associated with an increase in all-cause mortality.

The HSE’s recommended weekly low-risk alcohol guidelines are less than 11 standard drinks for women and 17 standard drinks for men. However, it is not a one-size fits all situation. “There is no single threshold of consumption that decides whether someone might experience problems due to alcohol,” says Dr Kersbergen. “Artificial distinctions between ‘normal drinkers’ and ‘problem drinkers’ can cause people to not recognise it when they are experiencing problems.” If you’re concerned, she advises taking The Alcohol Use Disorders Identification Test, which, she says, is “a helpful 10-question screening tool that is used to assess whether someone is at higher risk of alcohol problems”.

Drip-feeding your alcohol slowly over a week comes with its own issues. “It will reduce the acute risks such as accidents and, of course, hangovers,” says Dr Boniface. “But drinking on a daily basis is also not advisable in terms of habit forming, so it’s good to have alcohol-free days every week.” This limits exposure to the psychological phenomenon known as the “alcohol priming effect” whereby, Dr Kersbergen says: “Drinking even a small dose of alcohol can cause people to drink more, even if they didn’t intend to, due to increased craving and reduced inhibition. Someone who wants to cut down on drinking could therefore find it easier to not drink at all on a day than to drink only one drink.”

If you don’t want to give it up entirely, perhaps the trick is to balance the (relatively) small health risks of low consumption against the fact that having a glass of red with some friends remains a lot nicer than the other health risks we are routinely exposed to.

“Alcohol is the best drug for socialising that we know of,” says Prof Nutt. “And the whole history of humanity is socialising – we’re an enormously social species and alcohol facilitates that.

“The problem is that about 10-15 per cent of people really struggle to control their drinking and quite a few people drink more than they should without knowing it.”

Prof Nutt suggests two things. “First, you should be aware of how much you drink, in the same way you’re aware of your weight and waistline, and try to reduce it if necessary.” The second point may take some practice: “Never have a drink that doesn’t give you value. Most people have one drink and carry on – but most of the value comes from that first drink.” – Guardian

Professor David Nutt’s book Drink? The New Science of Alcohol and Your Health is available now