10% off €30 OR 15% off €40
What should you eat to keep your gut healthy? And can bacteria really be good for you?
With the help of Holland & Barrett nutritionist, Isabel Tarrant, we delve into the science of digestion and reveal some of the best foods for gut health.
We’ll also find out why fermented foods are the hottest new wellness trend – and how to include them in your diet to work towards a healthy gut.
The gut is a nine-metre-long tube that starts at the mouth, moves from the oesophagus to the stomach, through the small and large intestines, and ends at the back passage.
It’s where digestion takes place, and this involves three important processes:
The diversity of our gut bacteria is established at the very start of our development... but it can be altered by multiple factors.
Our gut microbiome begins to develop when we are still in the womb.1
It is very sensitive, and something as small as a baby being delivered vaginally vs being delivered by caesarean can affect which strain of bacteria are dominant in our system.
It then continues to evolve over time, becoming relatively stable once we’re around 3 years old.2
Multiple factors can affect our microbiome throughout our lives. The most common is our diet:
Right from the start, when we drink either breast milk or baby formula, our diet affects our gut bacteria.
For instance, breastfed babies tend to have better immunity and more diverse gut bacteria than those who are fed formula.3 4
Vegetarian and vegan diets have also been found to be associated with better bacteria diversity than a non-vegetarian diet.5
Eating probiotic and prebiotic sources, such as fermented foods, in appropriate doses have also been seen to cause specific changes in the structure of our gut microbiota and may benefit our health.6
For most people, a balanced and gut-friendly diet is the easiest and most effective way of keep our microbiome in check.
In the gut exists a thriving community of bacteria. As well as aiding digestion, they provide essential support for immune functioning, your skin, and brain health.
“We have approximately 100 trillion live bacteria living inside of us – this equates to 2kg of our body weight,” says Isabel Tarrant, Holland & Barrett nutritionist. “These helpful bacteria thrive by feeding off the food we eat. So, food is essential not only to feed and fuel us, but also to feed and fuel our friendly gut bacteria.”
But how does our gut activity impact our overall health and wellness?
A staggering 70% of our immune cells are in our gut.7
As a result, problems in your gastrointestinal tract can make you more susceptible to feeling run down or picking up illnesses.
“Friendly bacteria produce metabolites, such as short chain fatty acids. They play a crucial role in regulating T cells – the key peace-keeper cells of our immune system,” says Isabel. “Moreover, our gut bacteria produce compounds which support the healthy functioning of white blood cells, known as macrophages.”
The health of your gut microbiome impacts cognitive function and mood. This is down to a two-way relationship between the gut and the brain, known as the gut-brain axis.
“Bacteria in the gut modulates the activity of various chemicals in the brain, known as neurotransmitters. For example, it’s estimated that 90% of the ‘happy hormone’, serotonin, is made in the gut,” Isabel explains. “Research shows that individuals with anxiety, depression, and autism tend to have greater imbalance in their gut, with more negative bacteria than positive, compared to healthy individuals.” 8
There’s a strong relationship between the composition of your gut bacteria and sleep quality:
“Imbalances in the gut microbiome are associated with increased risk of sleep disturbances and poorer sleep quality,” says Isabel. “This is due to the interaction between gut bacteria and the regulation of sleep hormones.”9
Gut bacteria produce compounds known as short-chain fatty acids (SCFAs), which influence the production of the hormones responsible for the feeling of hunger and fullness.
“Individuals with a healthy gut bacteria composition tend to also produce more SCFAs, which leads to reduced hunger and increased fullness,” Isabel says. “This has a direct impact on eating habits and weight.
Research shows a striking difference between the gut bacteria of overweight and lean individuals.” 10
It’s estimated that, at any one time, about 4 in 10 people have at least one problematic digestive symptom. 11
These symptoms typically include:
As a starting point, you may want to include these good gut foods in your diet:
High-fibre foods such as fruits, vegetables, wholegrains, beans, and legumes may help to feed gut bacteria, allowing them to thrive and grow.
“Eating the rainbow” is a great way to ensure you get a range of all the vitamins and minerals you need. But it’s also a way to get phytochemicals – certain chemicals produced by plants that may contribute towards keeping us healthy. 12
The different phytochemicals found in coloured fruits and vegetables can help to encourage the production of a diverse range of positive bacteria in your gut.
Prebiotic foods such as garlic, onion, chickpeas, beans, artichoke, banana, and leeks are special fibres that good gut bacteria love to feed on.
The live bacteria in foods such as sauerkraut, live yoghurt, kombucha, kefir, and tempeh contribute to a healthy gut microbiome.
Alternatively, look out for probiotic supplements with a variety of bacterial strains and a high potency of bacteria.
These antioxidants are found in certain plant foods, including berries, purple carrots, spinach, green tea, grapes, and dark chocolate.
They are broken down by gut bacteria to produce compounds that can support immune functioning and brain health. 13 14
“Gut health foods” aren’t a magic solution, but consuming them often can help keep your microbiome at its strongest and most diverse. Adding a few into your daily diet could introduce a whole host of beneficial bacteria into your gut.
Read on for our top 9 gut health-supporting foods...
Ah, avocados… not just a food trend, they’re packed with gut-friendly nutrients, too.
As well as being a source of “good” fats, one avocado contains a whopping 13g fibre, helping you on the way to a happy gut.15
But it doesn’t end there! Research conducted by the University of Illinois from 2020 found that trial participants who ate an avocado every day had a more diverse gut microbiome, which helps to break down fibre and produce gut-healthy metabolites. 16
As we mentioned before, legumes are a great way to help your gut.
And one of the most versatile (and tasty) form of legumes are lentils. With approximately 15g fibre per cooked cup, they’re a great way to increase your fibre intake and provide support to improve your gut health.17
Scientists have recognised that lentils are a source of prebiotic carbohydrates, which are ingredients that allow for change in the makeup or activity of the gut microflora. 18 19
Perfect in chillis, curries, and stews, black beans are another great gut health-supporting food. With roughly 15g fibre per cooked cup, you won’t want to skimp on them! 20
One study from 2020 found that the resistant starch in black beans increased the level of Clostridia class bacteria – a potential type of bacteria for probiotic use. 21
Porridge has remained a classic breakfast for years... and for good reason. Oats are one of the best foods that can help digestion, as there is 5g fibre per 50g serving.22
But it’s not just any kind of fibre. The type that is found in oats is called soluble fibre, but specifically one called beta-glucan.
This has been shown to support gut health by increasing the level of “good” bacteria in the gut (Lactobacilli and Bifidobacteria).23 24
Everyone’s favourite cinema snack is actually healthier than you might think. Who knew popcorn could be one of the best foods for gut health?
Although - just to be clear - we’re not talking about the kind covered in butter, sugar, and salt.
Pure, air-popped popcorn without any added sugar, fats, or chemicals contains an impressive 14.5g fibre per 100g.25
Hailed as a superfood, chia seeds have become super popular in the health industry.
One of the main benefits they have to offer is their fibre content. In a 25g serving (or just under two tablespoons’ worth), there is approximately 8.6g fibre. 26
Specifically, the fibre in chia seeds is also a soluble fibre. .
This means that it feeds the gut bacteria, helping it to work at its best. 27
As well as boasting 6.9g fibre in two servings (46 almonds), they’ve also been shown to have prebiotic effects on the gut 28
Scientists have observed that almonds can improve the microbiota profile and change intestinal bacterial activity.29
The key to most delicious meals, garlic isn’t just good for the tastebuds – it’s potentially good for the gut, too. Some studies have shown garlic to help with the growth of bifidobacteria in the gut. 30
Equally as important in cooking as garlic, onions also offer more bang for your buck than you might think.
They’rea source of inulin (a type of fibre) and fructooligosaccharides (FOS), which help to strengthen the gut flora. 31 32
Now we’re talking! The short answer is yes, but we think it’s important to provide you with a tad more detail.
Find out all about fermented food and how it can help your gut below.
Thousands of years ago, our ancestors discovered that sealing a food away from oxygen meant bacteria started eating the sugar and starch – turning it into acids or alcohol.
This preserved the food, but it also gave it a unique, tangy flavour6
We all eat fermented foods without really thinking about it. Yoghurt, beer, sourdough bread, sour cream, chutney, sauerkraut, and its Korean cousin, kimchi, all fall into the fermentation category. 33
Sometimes bacteria, like lactic acid, is added to aid the natural fermentation process.
It’s now thought that regularly including these foods in your diet could help keep your gut happy.
One of the benefits of fermented foods is that they are naturally teeming with the healthy bacteria your body needs – and scientists think this may play an important role in keeping your own community of friendly gut bugs thriving. 36
Each of us has over 100 trillion live bacteria in our gastrointestinal tract, aka our gut, which help our body to perform a number of different tasks. 37
However, our gut bacteria need to be balanced to work at their best. For example, there need to be enough good “live” bacteria to balance out the “bad” bacteria that make us ill.
Balanced gut bacteria can support the following systems in the body:
In a 2015 review, published in the journal Current Opinion in Gastroenterology, researchers found that having a varied community of gut bugs may play a role in easing a range of bowel conditions, including irritable bowel syndrome (IBS). 41
As well as helping your digestive health, feeding your gut bacteria may also support other aspects of your wellbeing – for example, your mental health.
In 2016, researchers at University College Cork reported that giving healthy people cocktails of friendly bacteria for four weeks altered their brain activity in MRI scans. Participants were less likely to experience negative thoughts when they felt low. 42 43
Milk fermentation became popular in the late 19th century, when the technology required to produce it on a commercial scale became available.
People have been practising cheese fermentation and milk fermentation for centuries to preserve dairy products, but the live bacteria is usually stripped from them via pasteurisation before they are sold.
However, there are some dairy products specifically fermented and processed to preserve the cultures of live bacteria, some of which we’ve listed below.
Food fermentation can have some pretty tasty (and healthy!) results. Here are 9 of the best fermented foods:
Kefir is a fermented dairy drink that shepherds used to drink in the Caucasus mountains. In Turkish, the word kefir means “good feeling”.
People make kefir by using starter grains called kefir grains, which contain live bacteria like lactic acid and yeast.
It also contains essential minerals, vitamins, amino acids, and enzymes.
It tastes a little like yoghurt, but is said to have even more benefits, and makes a good snack or breakfast. 44
Yoghurt is one of the best and most well-known fermented foods. It’s made from milk that’s been fermented with live, friendly bacteria, namely bifidobacteria and lactic acid bacteria. 45
It’s an easy way to get your daily dose of probiotics; try including it in your breakfast with berries and honey or as a satisfying snack with nuts or granola.
Make sure you’re buying the real deal, though, and go for yoghurts with “live” or “active” cultures, as some yoghurts will have been processed to kill the bacteria.
Buttermilk was more popular back in the day, but if you can get your hands on some now, it makes a fantastic, fermented treat.
You need to make sure it’s made in the traditional way, though.
Buttermilk is simply the leftover liquid you get when making butter and it’s full of vitamins, minerals, and live bacteria.
Most cheese has been fermented, but they don’t always contain probiotics.
This is because most of the cheese found in supermarkets will have been processed in a way that kills the live bacteria.
Friendly bacteria can sometimes survive the ageing process in some cheese types, including mozzarella, gouda, cottage cheese and cheddar. 46 47
Make sure you always check the label for live and active cultures, though, if you want some probiotic goodness along with the protein, vitamins and minerals cheese provides.
Soybean fermentation is another very popular way to enjoy fermented foods.
Fermenting soybeans has been a firm favourite in Asia for centuries, and recently we’ve been enjoying products like tempeh in the West, too.
Below is a little more information about fermented soy foods:
Tempeh is originally from Indonesia but has become popular all over the world for its high protein content and “meaty”, earthy taste.
It’s made by fermenting soybeans with a specific type of fungus, which creates its vitamin B12 content (that soybeans don’t naturally contain) and gives it its much-loved texture. 48
Vegans and vegetarians tend to be tempeh’s biggest fan, as it is an excellent form of animal-free protein and contains vitamin B12, which usually comes from animal foods like meat, fish, eggs, and dairy. 49
Miso is another fermented soybean product from Japan and is most popular for its use in miso soup.
It’s traditionally made by fermenting soybeans with a type of fungus called koji and salt, but it can also be made by mixing soybeans with rice, barley, and rye.
Miso is full of friendly live bacteria, as well as protein, vitamins, and minerals, including vitamins K and B12. 50
Vegetable fermentation has been around for centuries, as it’s a great way of preserving fresh produce through the winter without needing to use a fridge or freezer.
Only in the last hundred years or so have we discovered the full benefits of using bacteria in this process for our health.
You may have already experienced sauerkraut on your frankfurter sausage or Reuben sandwich, where it provides a deliciously sour and salty flavour.
Sauerkraut has been enjoyed by many European countries for centuries and is made by fermenting finely shredded cabbage with lactic acid bacteria.
Alongside its probiotic benefits, sauerkraut also provides fibre and vitamins, C and K, as well as sodium, manganese, and iron. 51
Make sure you choose unpasteurised sauerkraut, though, as pasteurisation kills any live bacteria.
Similar to sauerkraut, kimchi is another fermented vegetable dish (usually cabbage) but with a lot more seasoning.
It’s made by fermenting cabbage or other vegetables with Lactobacillus kimchi and other lactic acid bacteria, and then adding seasonings like red chilli pepper flakes, ginger, garlic, spring onion and salt.
As well as being a great source of probiotics, it also contains vitamin B2, vitamin K and iron. 52 53
Fermented drinks are rising in popularity as they are an easy way to enjoy probiotics, don’t require much prep, and are usually quite tasty, too!
Kombucha is popping up here, there, and everywhere in recent years as a tasty, drinkable way to get your fill of probiotics.
It’s made by fermenting black or green tea with bacteria and yeast.
This yeast fermentation process makes it naturally fizzy. Then, fruity flavours are usually added...
Researchers agree that a healthy community of gut bugs depends on eating a wide variety of different foods – so including some fermented foods in your diet is a good move. 54
“Free from” foods for a happy gut
Keeping your gut healthy is important for everyone – but it might be even more so if you have allergies or intolerances.
Or, you might just want a quick list of vegetarian, vegan, or gluten-free gut foods...
Vegan gut health foods
You’re in luck when it comes to finding vegan foods that benefit your gut – there are plenty out there!
Vegetarian gut health foods
Gluten-free gut health foods
Unless you’re sensitive to specific foods, you shouldn’t feel you have to cut anything out entirely for the sake of your gut health. The old rule is true: everything in moderation!
However, there are some groups of foods that can have a negative impact on your gut microbiome – so it may be worth considering your intake if you’re looking to keep your gut health on top form...
Alcohol can reduce beneficial bacteria in the gut and promotes the growth of negative microbial species. 55 56
This results in an imbalance in gut bacteria that can have a negative impact on immune functioning, digestion, sleep, mood and weight. 57
Studies show that a high intake of sugar suppresses the growth of positive bacteria. 58 As a result, you may expect a negative impact on your microbiome composition.
Common sweeteners, such as saccharin, aspartame and sorbitol, can prevent the growth of friendly bacteria in the gut. 59 This can cause negative harmful bacteria to thrive.
The advice in this article is for information only and should not replace medical care. Please check with your GP or healthcare professional before trying any supplements, treatments or remedies. Food supplements must not be used as a substitute for a varied and balanced diet and a healthy lifestyle.
Last updated: 9 February 2023