The seven worst drinks for your gut health (and what to have instead)

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2 days ago

Every year, new studies are published showing the crucial role played by the gut in our overall wellbeing. Our intestines are home to an ecosystem of bacteria, fungi and viruses collectively known as our gut microbiome which affects everything from our immune system to our mental health.
Research is revealing, too, that the modern Western diet can wreak havoc on our gut. Ultra-processed foods kill off our healthy microbes and encourage the growth of harmful ones, resulting in an imbalance – known as gut dysbiosis – that can ultimately lead to disease and illness.
Thankfully, the message about consuming gut-friendly foods is beginning to get through. But while many of us are dutifully eating kimchi or taking probiotics, it may not cross our minds that what we drink also has major repercussions on gut health.
'In general, people think less about the drinks they consume than they do about food,' says Prof Tim Spector, an epidemiologist, author and co-founder of science and nutrition company Zoe. 'It might be partially because they can't imagine that a small glass of something can contain as much added sugar as a highly processed chocolate bar.'
With many of us now trying to improve our diets with gut health in mind, could what we drink be undoing all our good work? 'Life is all about balance,' Prof Spector says, 'and we shouldn't get too obsessed with 'undoing' our good work. The most important thing is to switch out any unhealthy drinks that you drink regularly. A can of cola once a month or so won't be an issue, but if you're having a few a day, it certainly will.'
Here are the eight worst drinks for your gut health, and what to have instead.
1. Bottled iced tea
Tea, which is rich in beneficial polyphenols, is a gut-friendly drink. Ready-made, bottled iced teas, on the other hand, are at the opposite end of the health scale. 'Almost all the commercial iced teas are full of sugar, or artificial sweeteners, emulsifiers, stabilisers and artificial flavourings,' says Stephanie Moore, a clinical nutritionist, health coach and author of Eat Your Brain Happy.
'All these additives are increasingly seen as gut disruptive, even at very low levels. Most iced teas are essentially no better than fizzy drinks, even if they do contain tiny amounts of tea.'
What to have instead: home-made iced tea or tea infusions
You can make your own, gut-friendly iced tea by mixing tea, lemon and water in a jug with lots of ice cubes.
Moore recommends adding slices of lime or fresh ginger root to boiling water, allowing it to steep and then either drinking it as a tea or allowing it to cool. 'You get all the anti-inflammatory compounds and the polyphenols and the various compounds that are present in both. I often advise people to experiment with taking a big jug of water and adding cucumber, berries or mint, or small pieces of fruit, and letting it infuse. That way, you get the flavour without the sugar.'
2. Fizzy drinks
'Fizzy drinks – whether they contain sugar or artificial sweeteners – are robustly associated with poorer health,' says Prof Spector.
Their high sugar content disrupts blood-sugar levels and feeds the pathogens in our gut. 'We all have lots of good microbes and probably a few bad microbes hanging around in our microbiome,' Moore explains. 'The bad ones thrive on sugar. So if you're regularly consuming sugary drinks, these pathogens are being fed. They proliferate and crowd out your good microbes. That's when we become prone to bloating and general digestive problems.'
Diet drinks, she warns, are no better for your gut. 'They are now believed to disrupt the gut microbiome quite dramatically,' says Moore. 'They're man-made chemicals, so the gut microbes have no idea how to cope with them. It appears that in the process of breaking these chemicals down, which is the job of the microbes, some kind of toxic or noxious by-product is emitted that causes die-off of good microbes.'
What to have instead: kombucha or water kefir
'Water kefir or kombucha are great alternatives to boring water or sugary sodas and squashes,' says Moore. Kombucha is a cold, sparkling drink made from fermented tea, while water kefir is made with water and kefir grains. 'I particularly like the lemon and ginger water kefir made by a company called Agua De Madre. It's a really refreshing and healthy option.'
3. Oat milk
Oat milk has seen a dramatic rise in popularity, with sales jumping by 77 per cent in the past five years, mainly because people see it as a healthier option than dairy. Moore, however, is unconvinced. As far as I'm concerned, it might as well be a fruit juice,' she says.
'In the process of making it, you're squeezing out the sugars in the same way you do with a fruit juice, and removing all the beneficial fibre. Then, to make it suitable to use in tea and coffee, they add rapeseed oil or sunflower oil, and some kind of emulsifier. So you end up with a horrible combination of sugar and fat.'
What to have instead: full-fat dairy milk
'For those who are able to tolerate it, I always recommend regular milk,' says Moore. 'Some people can't have dairy because of digestive or genetic issues, but for most people, milk – organic, ideally – is fine in small amounts. I would always say full-fat, because it means you don't lose the fat-soluble vitamins contained in whole milk. And where people can, I would recommend unhomogenised. Homogenisation breaks down the fat particles in milk, which makes the fat less digestible and can cause indigestion and unpleasant side effects.'
Prof Spector is also a fan of dairy milk in small doses. 'Fermented milk drinks [such as kefir] are the best option for gut health,' he says, 'but consuming dairy in moderate amounts is also fine. There is evidence that drinking milk can strengthen your gut barrier, making sure that compounds that aren't supposed to reach your blood stay within the confines of your gut.'
4. Protein shakes
'These types of drinks tend to contain a wide variety of additives and flavourings that will not support gut health,' says Prof Spector. 'They also tend to contain no fibre or healthy plant compounds to feed your microbes.'
Moore is equally scathing about protein drinks that are usually highly processed, artificially flavoured and contain surprising amounts of sugars. 'They do often contain nutrients and minerals, but at levels that are so negligible, they really don't deserve a place there. They also contain artificial flavourings and artificial sweeteners. It's really important to check the ingredients.'
What to have instead: home-made protein drinks
'It's much better to make your own,' says Moore. 'Use a protein powder – whey or flavourless bone-broth powder – and just whizz that together with a bit of good quality milk and an egg yolk. Add some berries, a little bit of cocoa powder. You've got everything you want in there and it costs a fraction of the price.'
5. Fruit juice
'When I was a young doctor, I would drink orange juice virtually every morning, considering it a healthy option,' Prof Spector recalls. 'Sadly, as delicious as fruit juices are, they're not great for our overall health. The juicing process removes almost all the fibre, so the sugar is absorbed rapidly into your bloodstream, which can cause health issues in the long run.'
One 2025 study published in Nutrients found that juicing increased inflammation in the gut and permeability in the gut lining, negatively affecting the microbiome.
The same applies to smoothies, which may be filled with entirely natural ingredients but contain concentrated amounts of sugar and fructose. 'There is no such thing as a good fruit juice,' Moore says categorically. 'It's a sugar bomb.'
What to have instead: kefir
Kefir usually contains around 30 different strains of microbes, compared with yogurt, which only has four. It makes a good alternative to fruit juice as a breakfast drink and is high in protein.
6. Lager
The message is very simple: alcohol is damaging to your gut health. Lager may contain less alcohol than other drinks, but it has a very high sugar content, which brings with it a range of negative repercussions to the gut microbiome.
As Moore points out: 'While a lot of alcohol will be absorbed before it reaches the gut microbes, some will get through. The effect on your microbes will be loss of number and potentially loss of diversity. These microbes replace themselves very quickly, but if someone is drinking alcohol every night, say, it will be very damaging to the gut microbiome.'
What to have instead: Guinness or alcohol-free beer
'Sadly, alcohol in general is bad for your gut,' says Prof Spector. 'However, darker beers tend to have more polyphenols, so if you enjoy an occasional tipple, opt for something dark.' A good example is Guinness which is known to have high levels of polyphenols.
Alcohol-free beers are also growing in popularity, though Moore points out that they tend to have a high sugar content. 'The debate is then, 'Is the alcohol or the sugar worse for the gut microbiome?' I think either is probably fine in real moderation, but neither are great on a regular basis.'
7. Dark spirits
Dark spirits like whisky, brandy and rum are particularly harmful because they contain high levels of congeners, natural compounds that are associated with more hangover severity and gut inflammation. 'These congeners are chemical compounds that come from the process of making darker spirits, as opposed to vodka and gin,' says Moore.
What to have instead: tequila/mezcal
'All spirits, regardless of colour, are bad for your gut health,' warns Prof Spector. However, if you're looking for a slightly less destructive option, studies suggest that tequila and mezcal could be a comparatively healthier choice. 'Both are made from the agave plant, which is full of inulin, which is a very potent prebiotic fibre,' says Moore.
'If you want to drink a spirit, your best option is to drink tequila mixed with some water kefir. That way you've actually got live microbes in the water kefir and prebiotics in the tequila. So you could potentially be getting something beneficial from an alcoholic drink.'
What should we be drinking to maintain optimal gut health?
Water is the ideal option, but it can get boring so it makes sense to find tasty, healthy alternatives.
When it comes to gut health, the top choice is fermented drinks like kefir and kombucha which contain live microbes. 'Make sure you choose one that doesn't contain lots of additives and sugar, and make sure the label says 'live cultures' or 'live microbes,'' advises Prof Spector. 'If it has been pasteurised to extend shelf life, for instance, the microbes will be dead.'
Moore recommends high-quality matcha green tea powder. Matcha is 'rich in antioxidants, particularly something called epigallocatechin gallate (EGCG), which has anti-inflammatory properties. What's great about it is that you can either drink it as tea or mix it into smoothies.'
What about tea and coffee?
'Black tea contains a wide range of healthy plant compounds called polyphenols,' says Prof Spector. 'These include theaflavins, thearubigins and catechins, which may support gut and overall health. Studies show that regularly consuming tea can reduce the number of 'bad' bacteria and increase levels of more beneficial microbes. However, green tea seems to be better than black.'
Coffee, he adds, is also beneficial. 'It contains fibre and polyphenols, both of which can feed your gut microbiome. In fact, a study found one microbe called Lawsonibacter asaccharolyticus. This species was much more common in people who drank coffee and was associated with a marker of good metabolic and gut health. In general, it seems that drinking up to five cups per day can support your gut health. And if caffeine doesn't agree with you, decaffeinated coffee is just as good for your microbiome.'
The main problem with tea and coffee, of course, is what people put in them. Sugar should be cut out, ideally, and if you're drinking multiple cups per day, add only a small amount of milk – though Moore does point out that for some people, drinking black coffee on an empty stomach may not be advisable: 'It can be quite acidic and disruptive to the digestive system, so adding a bit of milk can soften it and help the body manage the acidity better.'
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