Alcohol guide: Risks, benefits and its effect on your brain

The weekly limit adds up to either six glasses of wine, six pints of moderate strength beer, or just under half a litre of Pimms

If you’re wondering what 14 units equates to, in booze terms it adds up to approximately either six glasses of wine, six pints of moderate strength beer, or just under half a litre of Pimms, if you’re feeling summery.

Yet regularly we are consuming quite a bit more than that. In 2023, a Parliamentary enquiry found that around 10 million people in England regularly exceed the recommended alcohol guidelines, which advise no more than 14 units per week, spread over at least three days.

But while we should all realistically try to limit our alcohol consumption, how much we can tolerate does depend partially on our genetics. And if you love a cocktail or a few glasses of wine on a warm summer’s day, it’s not all bad news, as research indicates there are some steps you can take to make your drinking a little more tolerable for the body.

So let’s dive in – what does alcohol do to the body and why?

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What are the short-term effects of alcohol? 

  • Relaxation

  • Lowered inhibitions

  • Poor sleep

  • Dehydration

  • Nausea

The effect on the brain

Alcohol has a potent impact on your brain chemistry, disrupting the balance of various chemical messengers which affects your feelings, thoughts, and behaviour. The first of these messengers to be impacted is called GABA (gamma-aminobutyric acid), one of the reasons why alcohol is such an effective relaxant.

“GABA acts like a sedative to calm the brain down, while another chemical called glutamate, excites the brain and makes it more active,” says Prof Anne Lingford-Hughes, an expert in addiction biology at Imperial College London.

The more you drink, the more this balance between GABA and glutamate becomes disrupted. The frontal parts of the brain, regions involved in attention and planning, are particularly sensitive to this shift which is why we become more impulsive and lose our inhibitions as we drink.

If you keep drinking, the shift in brain chemicals ultimately spreads to the cerebellum at the back of the head which we need to coordinate muscle movements. This is why people who drink to excess are more prone to having accidents and struggle to walk in a straight line.

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The effect on the body and sleep

But alcohol doesn’t just impact the brain. It can irritate the stomach lining and increase acid release, causing nausea, while it also acts as a diuretic, prompting the body to drain fluids from your blood through the kidneys, bladder, and ureters. If you don’t consume enough water with alcohol, you can wake up extremely dehydrated the next day.

It isn’t only excessive drinking which disrupts the body’s rhythms. A handful of drinks can still impact your sleep quality because of the elevated levels of glutamate, which have an excitatory effect on the brain. As a result, Dr Matthew Parker, a neuroscientist at the University of Surrey, suggests drinking earlier in the day instead of late in the evening.

“The longer your body has to metabolise the alcohol and excrete it before bed, the better for your sleep,” he says. “There are three reasons for this. First, alcohol has what we call a biphasic effect on sleep. It makes us drowsy and fall asleep quickly, but then disrupts sleep in the second part of the night, the period when our brains are active, trying to repair any low-level damage that occurs during the day, and consolidate our memories. Again, this is worse if the alcohol is consumed near bedtime.”

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What are the long-term effects on health?

  • Increased risk of dementia

  • Increased risk of several types of cancer

  • Weakened immune system

  • Pancreatic inflammation

  • Liver inflammation and scarring

  • Irregular heartbeat

  • Greater risk of stroke and high blood pressure

Regularly chugging more than 14 units can have wider consequences. “Excessive alcohol may lead to liver diseases such as fatty liver, cirrhosis and liver cancer,” says Clarissa Lenherr, a nutritionist. “It can also impact the production of digestive enzymes, impairing your body’s ability to absorb nutrients from your food.”

Worldwide, excessive alcohol consumption has been linked to around three million deaths per year, including more than 400,000 from cancer. In 2022, a study from scientists at Oxford Population Health indicated that alcohol is a direct cause of cancers in the head, neck, oesophagus, liver, colon and breast. Previous research has also shown that approximately 4 per cent of cancer cases in the UK are related to alcohol.

The major reason for this is because when the body breaks down alcohol, it releases a toxin called acetaldehyde which can both damage cells and also stop them from effectively repairing this damage. Research has also shown that alcohol can sensitise cells in the mouth and throat so that they absorb greater quantities of harmful chemicals, for example from tobacco smoke, one of the reasons why smoking and alcohol consumption work synergistically to increase cancer risk.

While excessive drinking can directly damage various internal organs, causing inflammation and scarring, the high calorie content of alcohol can also lead to elevated blood pressure over time and predispose you to cardiovascular diseases. “Alcohol itself is very calorific,” says Prof John Holmes, who directs the Sheffield Addictions Research Group. “Cutting down the alcohol content of your drinks is also a good way to cut out the calories and thus make them less damaging.

While moderate alcohol consumption is not thought to be connected with cognitive decline, consistently high alcohol consumption is a known risk factor for dementia.

“Heavy alcohol use over many years reduces the cognitive reserve you have as you age,” says Dr Ronald Petersen, who directs the Mayo Clinic Alzheimer’s Disease Research Centre. “As we age, things build up and we become less cognitively acute. Our brain can compensate for this to an extent but consistently drinking too much reduces this resilience.”

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Safe alcohol consumption guidelines

Prof Holmes recommends taking steps such as having fewer alcoholic drinks per day, planning to drink on fewer days, and having a dry month now and then to reset your relationship with alcohol. “Measuring your serving to limit how much you drink can help,” he says.

Dr Parker particularly recommends trying to stick to beer or wine, and avoiding spirits which offer few benefits. “Spirits are the worst of the lot,” he says. “Heavy spirit consumption is associated with very poor health outcomes.”

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Potential benefits of moderate alcohol consumption

  • Improving gut microbiome diversity

  • Better cardiovascular health

  • Better immune health

  • Health benefits of beer

To be clear, this remains a highly contentious subject with many scientists. However, in 2023 a new paper emerged in the journal Frontiers in Nutrition which suggested that the plant chemicals present in certain beers could be useful in improving the diversity of microbial species within the gut microbiome, as well as releasing anti-inflammatory chemicals, which could have some benefits for immune health.

The paper suggested this could be more the case for darker beers such as brown ales or Belgian beers, than industrially manufactured mass market products. Drinks like mead and artisan cider brands could also offer similar benefits due to the presence of sugars floating in the drink known as polysaccharides, which could act as fuel for healthy bacteria

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Health benefits of red wine 

Dr Parker says that there is evidence that red wine is the most beneficial of all alcoholic drinks due to its high content of plant chemicals. “Moderate consumption of red wine is associated with better cardiovascular health and seems to lower the risk of certain cancers and dementia,” he says. “Polyphenols seem to offer protective effects on these health outcomes primarily through increasing high-density lipoprotein cholesterol. Moderate beer consumption has also been associated with cardiovascular benefits, again owing to its polyphenol content. However, compared to wine, the overall benefits are less clear.”

However, scientists still conclude that overall, the potential harms of alcohol likely outweigh the benefits, and any positives likely arise from low consumption, meaning no more than a single glass. Drinking more than two alcoholic drinks at a time is thought to make the gut wall more permeable, which allows bacteria and other chemicals to move into the bloodstream and contribute to low-level inflammation.

Risks of alcohol misuse

As well as chronic illnesses, drinking too much alcohol can also have a range of short-term risks such as accidents due to impaired judgement, balance and vision. Dr Parker points out that people are two to five times more likely to be hospitalised following binge drinking episodes.

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How to drink responsibly

Even if you’re currently regularly surpassing the weekly 14-unit limit, Prof Holmes says that it’s never too late to cut your intake for the sake of your health.

“Everyone can benefit from drinking less,” he says. “Cutting your consumption by even a small amount, whether that’s planning to drink on fewer days or having a dry month to reset your relationship with alcohol, it can all reduce your risk of suffering harm.”

Dr Parker strongly recommends avoiding binge drinking, which constitutes as more than eight units in a single session for men and six units for women. “This not only dramatically increases the risk of acute and long-term health issues, even for those who drink moderately on other occasions, but it dramatically increases the risk of accident and injury as you’re far more likely to misjudge situations or have impaired reactions.”

He also recommends different hacks such as using apps to self-monitor your alcohol intake and set yourself boundaries, as well as being aware of the triggers which lead you to drink in excess. “These triggers vary from person to person,” he says. “Relaxing with a drink after a hard day can be very therapeutic, but a dysfunctional relationship between stress and alcohol is a common precursor to drinking getting out of hand. Recognising these triggers and avoiding them can prevent over-consumption.”

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Statins and alcohol

Research shows that there are no immediate problematic side effects from drinking alcohol while taking statins. However, consuming excessive amounts on a regular basis could become dangerous because some studies have indicated that statins can sometimes affect the liver.

“Before starting a statin, speak to a health professional about your alcohol consumption,” says Dr Unnati Desai, a national GP lead at Nuffield Health. There is no strict guideline to stop drinking alcohol when taking a statin, however, adds Dr Desai, “it is important to stay within the recommended limit of 14 units per week and ensure alcohol-free days by spreading alcoholic drinks over three or more days”.

Alcohol intolerance 

Some people metabolise alcohol less well than others, due to genetic variants which impact how much of an enzyme called ALDH2 they produce.

“People with low levels of ALDH2 activity experience more of a build-up of acetaldehyde,” says Dr Stuart Grice, a geneticist. “For people with some genetic make-ups, acetaldehyde levels can be between six to 19 times higher than normal and one study highlighted that individuals with genetically lower ALDH2 activity, who consume alcohol, have a 20 per cent higher risk of cancer.”

Dr Grice says that the higher amounts of acetaldehyde also stimulate the release of chemicals such as histamine and adrenaline which can lead to side effects from drinking such as excessive nausea, palpitations, facial flushing or particularly severe hangovers. Experiencing these symptoms, even when you have only consumed a moderate or low amount of alcohol, is a key indicator that you might be carrying genetic variants which make you more susceptible to its effects.

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Can you drink alcohol on antibiotics?

Research has shown that you shouldn’t drink alcohol when taking any of the following antibiotics:

  • Cefoperazone

  • Cefotetan

  • Griseofulvin

  • Isoniazid

  • Ketoconazole

  • Linezolid

  • Metronidazole

  • Tinidazole

This can lead to serious and potentially dangerous side effects ranging from excessive sweating to an elevated heartbeat, liver damage, high blood pressure, nausea, dizziness, severe headache, flushing and diarrhoea, because of how alcohol interacts with their chemical structure.

In general, alcohol is not thought to impact the efficacy of antibiotics. However, drinking alcohol while taking any antibiotic medication is not advisable as aside from the potential for side effects, some research suggests that it can delay infection recovery in other ways, for example through impacting sleep quality or energy levels.

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Does alcohol raise blood pressure?

In 2023, a study of more than 19,000 people across the United States, South Korea and Japan, found for the first time that both moderate and high alcohol intake can have an impact on blood pressure. This finding seemed to be particularly pronounced in people who were found to already have elevated blood pressure.

“Alcohol is certainly not the sole driver of increases in blood pressure,” says Marco Vinceti, a professor of epidemiology and public health at the University of Modena and Reggio Emilia University in Italy, who led the study. “However, our findings confirmed that it contributes in a meaningful way.”

The good news, however, is that the study also found no noticeable fluctuations in blood pressure between people who did not drink alcohol at all, and people who only consumed low amounts – suggesting that you still can have the odd drink or two without any cause for concern.

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