Alcohol is a central part of many cultures. It’s often what people turn to when they’re happy or sad, celebrating or commiserating. And many people can be tempted to overindulge during the festive season.
Still, despite its popularity and availability, alcohol is a potentially addictive toxin that can harm your health, including the health of your gut and its microbiome.
In this article, we explore the official alcohol guidelines and describe alcohol’s potential effects on your gut health. Finally, we offer tips to help you drink more safely during the festive season and beyond.
Your guide to units and how much is safe
To keep your health risks low, the UK Chief Medical Officers recommend drinking no more than 14 units of alcohol per week, regardless of your sex.
Still, these experts are clear that there’s ‘no definitively “safe” lower limit.’
Important note: While keeping your drinking within 14 units per week is relatively safe, these units should be spread throughout the week, not consumed in one day.
At the same time, it’s important to have no-drink days each week to give your body a rest.
What’s a unit?
According to the National Health Service (NHS), 1 unit of alcohol is 10 millilitres or 8 grams of pure alcohol. This is roughly what an adult body can process in 1 hour.
Here’s what this means in practical terms:
Spirits
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1 shot (25 ml) of a spirit, such as whiskey or vodka: 1 unit
Red, white and rosé wine
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1 small glass (125 ml at 12%): 1.5 units
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1 standard glass (175 ml at 12%): 2.1 units
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1 large glass (250 ml at 12%): 3 units
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1 bottle (750 ml at 12%): 9 units
Beer and cider
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330-ml bottle at 5%: 1.7 units
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440-ml can at 5%: 2.2 units
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500-ml can at 5%: 2.5 units
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1 pint of low-strength (3.5%): 2 units
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1 pint of higher-strength (6%): 3.4 units
If your tipple isn’t on this list, you can work out how many units a drink has using this formula: alcohol strength (%) x volume (ml) ÷ 1,000 = units.
Here’s an example for a small glass of wine:
12% x 125 ml = 1,500
1,500 ÷ 1,000 = 1.5 units
Handy tools for calculating and tracking units are available from Drink Aware.
Alcohol and your gut health
Drinking too much in one sitting or drinking frequently for weeks or months can cause a range of gut symptoms, including:
Acid reflux (heartburn)
Alcohol relaxes the ring of muscle that protects your oesophagus (food pipe) from stomach acid.
As this muscle relaxes, it allows stomach acid to rise into your oesophagus, damaging its tissues and causing pain.
Drinking alcohol frequently over time is also associated with gastroesophageal reflux disease (GERD). This is essentially a long-term version of acid reflux.
Gastritis (stomach inflammation)
Drinking alcohol increases your risk of an inflamed stomach.
The main symptom of gastritis is burning chest pain (like heartburn). It may also cause bloating, nausea and vomiting.
The symptoms of gastritis can last a few days or longer. If it happens repeatedly, damage from gastritis may increase the risk of stomach cancer.
Bloating
We’ll learn more about this later, but shifts in your gut microbiome caused by alcohol consumption can lead your microbiome to produce more gas. This, in turn, leads to bloating.
Meanwhile, carbonated (fizzy) alcoholic drinks, like beer and cider, can also lead to bloating. Any time you're consuming a lot of gas, you'll probably feel a bit bloated.
Other alcoholic drinks are often mixed with sugary or sweetened extras, like fruit juice or syrup, which can also trigger bloating.
In one study, which mostly included people with irritable bowel syndrome, beer consumption was linked to prolonged bloating, lasting 24–72 hours.
Diarrhoea
Because alcohol disrupts the normal functioning of your gut, it can cause diarrhoea.
For instance, alcohol can:
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draw water from your body into your gut, making your poo more runny
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cause inflammation, which can speed up the digestive process
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quicken the contractions that push food through your gut
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disrupt your community of gut microbes (more on this below)
Vomiting
Being sick is your body’s way of removing toxic compounds, such as alcohol.
While this method is highly effective, it’s also unpleasant. Plus, stomach acid can damage your teeth and the lining of your oesophagus as it passes through.
Alcohol and the gut barrier
One way alcohol can influence gut health is by making the lining of your gut more ‘leaky.’
This barrier is vital for keeping unwanted compounds from travelling into your blood. Because alcohol disturbs your gut’s lining, toxins and bacteria may reach your bloodstream and circulate throughout your body.
Your immune system identifies these stowaways and mounts a response, causing inflammation in your gut and beyond.
In addition, alcohol puts you at a higher risk of gut-related cancers, including oesophageal, stomach and colorectal cancer.
Alcohol and your gut microbes
Drinking alcohol can impact your gut microbiome in many ways.
Because alcohol is used in antibacterial sprays, it makes sense that it would upset the balance of the gut microbiome.
However, most alcohol in a drink is absorbed fairly early in its journey through your gut, so smaller amounts reach your large intestine, where most gut microbes live.
Part of the reason alcohol affects the the large intestine may involve its circulation in the bloodstream, including the blood vessels that supply the gut.
Because this is quite a niche area of research, scientists are still determining the effects of alcohol on the gut microbiome.
So far, research suggests that excessive alcohol intake can cause dysbiosis – an imbalance in the gut microbiome.
It can also promote the overgrowth of certain species. This leads to increased levels of toxins produced by bacteria, which cause inflammation.
To date, most research has focused on people with alcohol use disorder, which used to be called alcoholism.
The microbiome and alcohol use disorder
The National Institute on Alcohol Abuse and Alcoholism defines alcohol use disorder, or AUD, as an ‘impaired ability to stop or control alcohol use despite adverse social, occupational or health consequences.’
A review of studies on AUD and the microbiome found that people with the condition had lower levels of the friendly microbes Akkermansia muciniphila and Faecalibacterium prausnitzii.
The participants also had higher numbers of Enterobacteriaceae, which are associated with an increased risk of infection and certain chronic diseases.
Importantly, the scientists also noted a reduction in several friendly species that produce health-promoting short-chain fatty acids (SCFAs).
‘Good’ bacteria produce SCFAs as they digest fibre, and SCFAs have benefits throughout the body.
Gut microbiome and alcohol: Should you worry?
Research on AUD provides insights into alcohol’s effects on the gut microbiome. However, there’s been much less research into the effects for people who drink 14 units per week at most.
In general, the less you drink, the less impact alcohol is likely to have.
It’s also worth noting: for someone with AUD, other lifestyle factors may be influencing the gut microbiome.
Diet may be one factor, as people with AUD have a higher risk of malnutrition. Alcohol consumption can also significantly disrupt sleep, another influence on the gut microbiome.
This means that for people with AUD, gut microbiome changes might result from a combination of factors, not alcohol alone.
It’s also important to remember that your gut microbiome is resilient and can change rapidly.
If you’re worried that you might have overindulged, take some time to look after your gut by switching to plant-based foods, keeping hydrated and avoiding alcohol for a bit.
Can probiotics help?
Probiotics can support a healthy gut microbiome, and they can likely help rebalance an unbalanced microbiome.
However, there hasn't been much research into whether probiotics can reverse damage caused by alcohol.
In other words, taking a probiotic every day won’t protect you from the harm alcohol can cause.
Are some drinks healthier than others?
Technically, there’s no safe amount of alcohol. For your overall health, including your gut health, the most important thing is to stay within the 14-unit guidelines set out by the government’s health experts.
Still, some drinks may be more harmful than others. Spirits, for instance, contain the highest amount of alcohol per ml and don’t contain much else.
At the other end of the spectrum, red wine is the least bad for you, if you have it in moderation.
Thanks to the grape skins involved, red wine contains polyphenols. These are plant-defence compounds, and when you consume them, they can support your gut microbiome.
Rosé has fewer polyphenols, and white wine has even fewer. This is due to the limited time that grape skins are involved in fermentation.
Some beers, particularly darker beers and those fermented in more traditional ways, also contain polyphenols, although not as many as red wine.
Again, and it bears repeating, no alcoholic drink can truly be considered healthy.
9 tips to help you drink more safely
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Have a non-alcoholic drink, like a glass of water, between each alcoholic one.
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Set a limit before you go out, and stick to it.
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Choose drinks that are lower in alcohol.
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Think in units, so you can keep track of your intake.
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Instead of meeting up in a pub, suggest a walk or coffee.
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Opt for smaller drinks.
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Never drink on an empty stomach.
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If you can avoid it, don’t do rounds. They encourage you to drink more.
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Tell friends and family you’re cutting down, so they’ll help support you.
FAQs
Below, we answer common questions about alcohol’s effects on the body.
Can you cure a hangover?
The only way to avoid a hangover is to drink responsibly. Failing that, make sure to keep your fluid levels up, and get plenty of rest.
Is red wine healthy?
Red wine can’t be called ‘healthy’ because of its alcohol content.
Compared with other alcoholic drinks, it’s less unhealthy. This is due to the bioactive polyphenols that red wine contains. But it’s still not a health tonic.
How can I tell if I’m drinking too much?
If you’re regularly drinking more than 14 units per week, you might be drinking too much.
Anyone who is concerned about their drinking should speak with a doctor. The NHS also offers this useful list of contacts.
Summary
If you’re planning to drink, it’s best to have only a little and not too regularly. The UK’s official guidelines recommend drinking no more than 14 units per week.
Alcohol can cause a range of gut symptoms, including bloating, pain, stomach inflammation (gastritis) and changes in stool consistency.
It can also increase the ‘leakiness’ of your gut lining, causing further inflammation.
According to recent research, alcohol also seems to harm your gut microbiome. For instance, drinking too much is associated with reduced numbers of friendly microbes that produce SCFAs.
No alcoholic drinks are healthy. But red wine may be the least unhealthy, thanks to the polyphenols it contains. If you prefer beer, try a dark variety – these beers also contain some healthy plant compounds.
If you’re worried about overindulging, there are many ways to lower your intake. For instance, have non-alcoholic drinks between alcoholic drinks, and opt for smaller or lower-alcohol varieties.
If you’re concerned about your drinking, help is available, so let your doctor know.
To learn more about other health topics, visit Symprove’s Gut Hub.
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