Why fermented foods are good for gut health

Fermented foods have been enjoyed for thousands of years, but they're having a well-deserved moment in the spotlight in the health and wellness space right now. From tangy kimchi and live-cultured yoghurt to kombucha and sauerkraut, these foods are celebrated not only for their distinctive flavours but also for the powerful role they can play in supporting your gut health. 

Your gut is home to trillions of microorganisms that help digest food, support your immune system as well as other areas of health. Eating a wide variety of plant-based foods is one of the best ways to care for your gut, and fermented foods can be another simple addition to your routine, thanks to the live cultures they contain.

In this blog, we'll take a closer look at what fermented foods are, how they contribute to a healthy gut, and recommend some of the best options to add to your shopping list.

What are fermented foods?

Foods and drinks created through the natural process of fermentation undergo changes that give them unique flavours and properties. During fermentation, microorganisms such as bacteria and yeast break down the natural sugars in food, which not only helps preserve the food but also creates its distinctive flavour, texture and beneficial live cultures.

Fermentation has been used for thousands of years to preserve ingredients, long before refrigeration existed. Today, it's valued just as much for the nutritional benefits it can offer as for the unique taste it brings to your everyday meals.

Some of the most popular fermented foods include live yoghurt, kefir, sauerkraut, kimchi, miso, and kombucha. While not all fermented foods contain live cultures by the time they reach your plate, many do, making them a simple and delicious way to support a varied, balanced diet.

How do fermented foods support gut health?

Your gut microbiome is made up of trillions of microorganisms that help keep your digestive system working smoothly. It helps break down food, produces certain vitamins, and helps protect against harmful bacteria. The food you eat has a big influence on how well your gut microbiome functions, which is why a diet rich in a variety of fibre-rich and fermented foods helps nourish the beneficial bacteria already living in your gut.

Fermented foods deliver live probiotics to your gut that diversify your gut microbiome and help get rid of harmful bacteria when eaten as part of a healthy diet. Some fermented foods also contain compounds produced during the fermentation process, such as organic acids and bioactive peptides that also help to support digestion and gut health.

It's worth remembering that fermented foods work best alongside other gut-friendly habits rather than as a quick fix. Eating plenty of fibre-rich foods, including wholegrains, nuts, seeds, fruit and vegetables, staying active, managing stress and getting enough sleep all help create an environment where your gut microbiome can flourish.

What are the benefits of fermented foods for gut health?

While research into the gut microbiome is still evolving, many studies suggest that regularly eating fermented foods as part of a healthy, balanced diet may have many benefits for digestive health.

Supports a diverse gut microbiome

In a 2021 clinical trial, people who ate around six servings of fermented foods a day for 10 weeks experienced an increase in gut microbiome diversity and lower levels of inflammation. Greater microbial diversity is generally considered a sign of a healthy gut and has been linked to better overall health.

Introduces beneficial live cultures

Many fermented foods, including live yoghurt, kefir, kimchi and sauerkraut, naturally contain live probiotics. Although these microbes don't usually stay in the gut permanently, they can interact with your existing gut bacteria as they pass through the digestive system, helping to support a healthy gut environment.

Helps support healthy digestion

Some evidence suggests that fermented foods may help improve digestive comfort. A 2024 study found that people who regularly consumed fermented foods experienced improvements in bowel movement frequency, stool consistency and symptoms such as bloating and constipation. 

Fermentation creates beneficial compounds

The fermentation process doesn't just add live cultures, it also produces naturally occurring compounds such as organic acids, enzymes and bioactive peptides. These compounds may help support digestion, improve nutrient availability, and contribute to a healthy gut environment.

Easy way to add variety to your diet

Eating a wide range of foods is one of the best ways to support your gut microbiome. Adding different fermented foods throughout the week, whether that's kefir at breakfast, miso in soups or kimchi alongside dinner, can increase the variety in your diet while introducing new flavours and beneficial microorganisms. When paired with plenty of fibre-rich foods, such as wholegrains, fruit and vegetables, you can give even greater support to your gut.

Are there any risks to eating fermented foods?

For most people, fermented foods are a safe and nutritious addition to a balanced diet. However, if you're new to them, it's a good idea to introduce them gradually.

Because fermented foods contain live cultures and can be rich in fibre, eating large amounts too quickly may cause temporary digestive issues like bloating, gas or changes in bowel habits. Starting with a small serving and increasing it slowly can help your gut adjust.

It's also worth remembering that some fermented foods can be high in salt. Foods like kimchi, sauerkraut and miso are often made using salt as part of the fermentation process, so they should be enjoyed in moderation, particularly if you're watching your salt intake. Similarly, some kombuchas and flavoured yoghurts can be high in added sugar, so it's worth checking the ingredients and nutrition label when shopping.

Not all fermented foods are the same, either. Some products are pasteurised after fermentation, which can destroy the live cultures they naturally contain. If you're looking to benefit from live microorganisms, choose products labelled with phrases such as ‘contains live and active cultures’.

What are the best fermented foods to eat?

There's not one "best" fermented food for gut health; every fermented food has its own benefits, nutrients, and flavours. The key is to incorporate as many fermented foods as possible into a balanced diet. Below we have listed a few of the most popular fermented foods that are easy to get hold of so you can start adding these gut-friendly foods into your daily routine.

Live yoghurt

Yoghurt that contains live cultures is one of the easiest fermented foods to include in your diet. Made by fermenting milk with beneficial bacteria, yoghurt, specifically natural or Greek yoghurt, naturally contains live cultures that can help support a healthy gut microbiome. Make sure to choose natural or Greek yoghurts that have no added sugar (often hidden in flavourings) and look for labels that say ‘live and active cultures’.

Kefir

Often described as a drinkable yoghurt, kefir is made by fermenting milk or water with kefir grains. It contains a wider variety of beneficial bacteria and yeasts than yoghurt, making it one of the richest sources of live cultures.

Sauerkraut

Sauerkraut is made by fermenting finely shredded cabbage with salt. When it's sold raw and unpasteurised, it contains millions of naturally occurring live cultures, as well as fibre to help feed your gut bacteria. Add a spoonful to salads, sandwiches or grain bowls for a tangy crunch.