Impact of caffeine on the gut
Impact of caffeine on the gut

How Caffeine Can Impact The Gut

According to The British Coffee Association, 95 million cups of coffee are consumed every day in the UK! And one of the key components that drives this demand is Caffeine – the world’s most commonly used drug! (1) And whilst many of us enjoy a cup of coffee or tea, do you actually know how caffeine is impacting the gut? Read on to find out more.



Caffeine is a stimulant found naturally in herbs, coffee beans and cacao (aka chocolate!). 

It works its magic in two main ways:

  1. First by halting the effects of one of our neurotransmitters that contributes to relaxation and tiredness– adenosine. 
  2. Secondly, caffeine prompts us to produce our stress hormones, cortisol, adrenalin and others which is why some say that caffeine makes them feel alert, energised and focused.

We do need to be mindful that there is an upper limit with caffeine consumption, there really is such a thing as “too much of a good thing”. The recommended intake of caffeine for adults is no more than 400mg which is about:

  • 4 cups of standard coffee
  • 7/8 cups of lightly brewed tea

If you are pregnant, trying to conceive or under the age of 18 then consume no more than 200mg a day.



Caffeine can be found in more than just coffee, it is also found in Green tea, black tea, matcha, dark chocolate, fizzy drinks such as diet colas and full-fat colas, energy drinks, some ice cream, protein bars and even hidden in some medications.



There are more than 1000 bioactive molecules in coffee, with lots of other beneficial things including Vitamin B2, Magnesium and Polyphenols. So how do these chemicals affect the gut?


Compounds from caffeine including polyphenols and fibres can exert some effects in the large intestine, where they are fermented by microbes. 

Small scale studies have linked high caffeine consumption with a higher amount of anti-inflammatory bacteria such as Faecalibacterium and Roseburia, and with lower levels of potentially harmful Erysipelatoclostridium. (4)

The link between coffee and the microbiome may be dose-dependent. A PREDICT study showed that individuals who drank four cups of coffee per day tended to have higher microbiome diversity, compared with people who drank fewer cups or none at all. This may be linked to the fact that coffee contains polyphenol and soluble fibre compounds that act as food for our beneficial “good” gut microbes rather than due to the caffeine content. (5)


One of the most obvious effects of coffee is its ability to keep things moving through the gut. Caffeine activates contractions in the digestive tract, whilst other compounds in coffee stimulate the production of stomach acid. 

Both of these help to move food through the gut and keep you regular, nearly 30% of people say that drinking coffee makes them need to poop within 30 minutes! (6)

Some individuals still have this reaction even when drinking decaf- this could be down to the small amounts of fibre, the hot water or learned mechanism. 


Caffeine increases stomach acid production, stimulating motor activity levels in the gut, leading to diarrhoea. Those who regularly get loose bowel movements and have diarrhoea-predominant IBS will be more affected by caffeine than those with constipation-prevalent IBS. 



Regular consumption can lead to a tolerance, where a higher dosage is required to get the same energising effects as before. And ever tried going cold turkey on caffeine? Abstinence can lead to withdrawal symptoms such as headaches, nausea and irritation. 

Consuming caffeine prompts the secretion of cortisol, our stress hormone, and whilst a little bit of this can be stimulating and excitatory, we need to ensure we aren’t getting all excited and energised at the wrong time of the day.  An elevation in Cortisol late at night may potentially impact your sleep, anxiety and stress levels. 

However, even though caffeine can be disturbing your sleep, it doesn’t mean that it’s time to cut it out completely. 



Here are a few ideas for managing your coffee consumption:

  • Set a cut off time for coffee at 2 pm. Caffeine has a half-life of around 6-10 hours, which in other words it means it takes up to 6 hours for half the caffeine consumed to be removed from the body. For this reason, it’s best to limit caffeine consumption for the morning hours and limit it to early afternoon at the latest.


  • Limit caffeine to a maximum of 400mg per day. Adults shouldn’t be consuming more than 400 mg of caffeine per day, which equals about four cups of coffee or eight cups of black or green tea. Too much caffeine can trigger nausea, stomach upset, anxiety and irritability. 


  • Try out naturally caffeine-free alternatives such as turmeric lattes, chicory root coffee, tulsi tea or rooibos. Find my favourite’s here




Beverage/ food Caffeine per serving
Single Espresso  80mg
Starbucks Americano 225mg
Cup of black tea 50-75mg
Green Tea 28mg
Can of Coke 32mg
Dark chocolate 45-59%                                    43mg per 100g
Darker chocolate 70-85%        80mg per 100g                                      



One of the new trends is how to get even more out of your daily coffee. Forget alternative milks or froth to creamy ratio, the new buzz entails pimping your coffee with everything from sprinkling ‘superfoods’ in place of chocolate to adding herbs and mushrooms to the mix.

I am all for nutritional boosts and using the power of herbs and nutrients to optimise our health. So read below for my top super coffee add-ins:


Collagen not only gives us a dose of protein, but it can also help with skin, joint and digestive health. Adding collagen to your cup of coffee in the morning can help us balance our blood sugar levels and therefore our energy. This can be a good option for those who find they slump in energy quite quickly after coffee or who find that caffeine causes overstimulation. 

Collagen may also help with intestinal permeability, so adding in some collagen to your caffeine source may also be good for the gut!

Collagen is tasteless and doesn’t change the texture of your drink when you stir or blend it in. Most collagen powders come from bovine sources, so if you are a pescatarian, reach for a marine collagen source. My favourite is Planet Paleo powders (they come in on-the-go sachets too) found here. 



Medicinal mushrooms such as Cordyceps, Reishi and Chaga are famed for being fantastic for immunity, stamina and importantly, energy. Adding them to your morning brew can help offset the jittery effects of coffee and give you an additional energy lift. I love the Four Sigmatic mushroom coffee mix found here.



Caffeine is great for concentration, improving attention and focus. The downsides can be increased heart rate, blood pressure, and that anxious/jittery feeling. Insert L-Theanine, an amino acid that can help counteract some of these side effects.

L Theanine is a relaxant that can reduce heart rate and blood pressure, improve concentration and promote alpha brain waves (associated with relaxation). When combined with caffeine there is a potential pronounced synergistic effect. This means you can experience intensified focus, awareness and energy, alongside reduced stress and improved mental endurance. 

If you are taking any medication, pregnant, breastfeeding, trying to conceive or have a diagnosed condition, please check in with your health care practitioner before adding herbs/plants/supplements to your diet.




If you think your morning coffee ritual is a bad habit that needs to be binned, think twice. There are some clear health benefits associated with having your daily coffee, although everyone is individual and will react to it differently.

However, if you do choose to drink coffee there are so many artificially flavoured milks, creamers and questionable sugars out there that popular high street coffee chains use. Ensure you are consuming it in the right quantities and in the most natural way possible. 

If you suffer from anxiety or have trouble getting to sleep at night, switching to decaf is a great option. In addition, if you are following a low FODMAP diet to manage your gut symptoms, make sure you are opting for low FODMAP coffee options if you can’t go without it. And potentially try caffeine free if you notice it impacts your gut.

If you still think coffee is triggering your symptoms, then eliminate it completely for a couple of weeks to see if your symptoms improve. 


References: (1) (2) (3) (4) (5) (6)

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Hi there

London Nutritionist Clarissa Lenherr

I’m Clarissa, a registered nutritionist (mBANT) and workplace wellness expert. In my practice, I have helped hundreds of clients reach optimal health through creating sustainable, effective habits and dietary adjustments. My aim is to empower people with the skills, tools and knowledge to take their health into their own hands and feel the happiest, healthiest versions of themselves. Featured in The Daily Mail, Women’s Health, The Telegraph, and more.




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