Bowls of fermented foods against a white background

Fermentation: the secret to good gut health?

Find out why fermented foods are the hottest new wellness trend – and how to include them in your diet.

Fermentation may be the latest health buzzword but there’s nothing new about it – fermenting was originally simply a practical way of preserving foods. But now we know that fermenting foods is not just a clever way of keeping perishable foods edible – it’s a clever (and tasty!) way to enrich your body’s natural bacteria and support your digestive system.

What are fermented foods?

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 flavour.1 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.2 Other fermented products may be less familiar to you, including kefir – a milk drink made from a combination of fermented bacteria and yeast – and kombucha, a fermented sweet tea drink.3 4

The health benefits of fermented foods

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.5

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. However, our gut bacteria need to be balanced for it to work at its best, e.g. there needs to be enough good ‘live’ bacteria to balance out the ‘bad’ bacteria that  make us ill. Balanced gut bacteria support the following systems in the body:

  • Immune system
  • Cardiovascular system
  • Sleep system
  • Digestive system
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.6 As well as helping your digestive health, feeding your gut bacteria may in turn boost 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.7 8 And we know that in China, Japan and Korea, where people traditionally eat lots of fermented foods, such as kimchi and miso soup, bowel complications are far less common.9 Read more about the health benefits of a healthy and balanced gut in our article on How to have a happy gut.

What causes gut bacteria to become unbalanced?

The diversity of our gut bacteria is established at the very start of our development but can be altered by multiple factors. Our gut microbiome begins to develop when we are still growing in our mother’s womb. 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 to become relatively stable at around 3 years old.10

However, there are several lifestyle factors that can alter our bacteria, including:

Antibiotic exposure

In many countries, including the UK, antibiotics are also given to farm animals to increase their growth and weight and protect them from illness. We then eat them, potentially exposing ourselves to antibiotics; which are essential against harmful bacteria, but do not discriminate, and affect levels of our good bacteria too. However, there is no doubt that antibiotics are essential against certain bacteria-caused infections and you should always follow the advice of your GP on this subject.11


Right from the start when we drink either breast milk or baby formula, our diet affects our gut bacteria. For instance, breast fed babies tend to have better immunity and a more diverse gut bacteria than those who are fed a formula. Vegetarian and vegan diets have also been found to be associated with better bacteria diversity than a non-vegetarian diet. Eating probiotics and prebiotics, such as fermented foods, in appropriate doses have also been seen to cause specific changes in the structure of our gut microbiota and benefit our health.10

How to eat more fermented foods

Researchers agree 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. Here are some everyday ideas for gut health:11

Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.

Shop Vitamins & Supplements

Last updated: 15 May 2020

Related Topics

Digestive Health