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What is fermenting?

Fermentation is an ancient technique for preserving food and drinks that has been practiced since long before the days of refrigeration. During fermentation, micro-organisms like bacteria, yeast or fungi convert organic compounds like sugars and starch into alcohol or acids. These act as natural preservatives and improve the taste and texture of fermented foods, leaving them with a distinctive strong, salty and slightly sour flavour.

There are two main methods of fermentation: spontaneous, when the micro-organisms naturally present in the food or environment initiate fermentation, or secondly by the addition of a ‘starter culture’. An example of a spontaneous fermentation would be in the production of kimchi or sauerkraut, whereas a starter culture is used to produce kefir or natto.

Fermentation is used in the production of many of the foods and drinks we enjoy, such as yogurt and cheese.

Discover more tips for digestive health and browse our gut-healthy recipes. Want to have a go at making your own ferments? Follow our guides for how to make kombucha, how to make kefir and our quick kimchi. Also check out our health and nutrition hub for more recipe inspiration and advice on special diets.

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Fermenting benefits may include...

  1. A source of beneficial probiotic and prebiotic bacteria.
  2. Fermented foods are easier for the body to digest.
  3. It removes ‘anti-nutrients’ which enhances the availability of certain nutrients.
  4. It may improve symptoms of stress, anxiety and depression.
  5. May support heart health and lower risk of heart disease.
  6. May support immune function and reduce risk of infection.
  7. Fermenting foods may aid weight loss.

Nutritional profile of fermented foods

There are many variables involved in the fermentation process. These include the micro-organisms at work, the nutritional contribution of the ingredients used and the environmental conditions to which the food is exposed. Consequently, these factors give rise to thousands of different variations of fermented food, with associated differences in their nutritional contribution and microbial diversity.


What are the top health benefits of fermenting?

1. Source of beneficial bacteria

Most fermented foods contribute bacteria that have a potential probiotic effect. This means that these bacteria may help restore the balance of bacteria in your gut, support digestive health and alleviate any digestive issues.

Probiotic amounts will vary, however, and the number of bacteria that arrive in the gut, where they can be of benefit, will depend on a number of factors, including the food in which they are delivered, with those supplying fibres referred to as prebiotic, being the most beneficial.

2. Easier to digest

Thanks to the bacterial breakdown of some of the natural sugars and starches, fermented foods are easier for us to digest. For example, fermentation breaks down the lactose in milk to simpler sugars – glucose and galactose – this means if you are lactose intolerant, products like yogurt, kefir and cheese may be acceptable for you.

3. Improves the availability of nutrients

When we ferment certain foods, we help increase their health potential. This includes both producing more vitamins and minerals and making them more available for our bodies to absorb. This is because some natural compounds, like phytic acid found in legumes including soy beans, may inhibit our absorption of nutrients like iron and zinc. Fermentation removes these ‘anti-nutrients’, making their nutritional content easier for us to access. Similar benefits have been seen with sourdough, with improvements in mineral availability, lower glycaemic responses and a greater break down of proteins all being cited.

Additionally, by boosting the beneficial bacteria in your gut, you may promote their ability to manufacture B vitamins and vitamin K.

Homemade yogurt

4. May improve mood and behaviour

Our understanding of the gut and how it impacts our mood and behaviour is fast evolving, and it would appear that fermented foods may play an important part. Certain strains of probiotic bacteria, including Lactobacillis helveticus and Bifidobacteria longum, commonly found in fermented foods, may improve symptoms of anxiety and depression.

Another strain, Lactobacillis casei Shirota, may also influence the production of cortisol and minimise physical symptoms of stress.

5. May support heart health

Consuming fermented foods as part of a healthy, balanced diet appears to be associated with a lower risk of heart disease. The mechanisms at play may include modest reductions in blood pressure and improvements in cholesterol balance.

6. May support immune function

Including a range of fermented foods in your diet may support your immune function and reduce your risk of infection. Studies suggest beneficial gut bacteria, in the form of probiotic supplements, may be particularly useful in reducing upper respiratory infections. Whether this effect is replicated through the inclusion of fermented foods in the diet is not yet known.

7. May support weight loss

Although more research is needed some studies suggest certain strains of beneficial bacteria may aid weight loss and reduce belly fat.

Is fermented food safe for everyone?

Fermented foods are safe for the majority of people, but some individuals, such as those with a histamine intolerance, may experience side effects. Furthermore, if fermented foods are new to you or you are not used to a fibre-rich diet, you may experience symptoms such as bloating and flatulence.

Introducing fermented foods to someone who is critically ill or immune-compromised should be done with caution and under the guidance of a GP or other healthcare professional.

When making your own fermented foods, always follow recipes and be sure to use sterile equipment, and follow fermentation times and temperatures carefully.

Overall, is fermenting good for you?

As our understanding of gut health evolves, a body of research is building to indicate that fermented foods may play an important part in overall health, from being a source of good bacteria, to enhancing the body’s ability to absorb certain nutrients. Fermented foods can also play a contributing role in boosting immunity, aiding weight loss and improving symptoms of stress, anxiety and depression. As such, these foods would be a good addition to a diet, though be mindful that the nutritional contribution and microbial diversity of fermented foods varies.

Read more like this

Top probiotic foods
Top 12 healthiest fermented foods
What are probiotics and what do they do?
Top 5 health benefits of kombucha
The health benefits of kefir
The health benefits of miso
The health benefits of sourdough

Do you make your own ferments? Share your successes in the comments below…

Kerry Torrens is a qualified Nutritionist (MBANT) with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food.


All health content on is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact your local health care provider. See our website terms and conditions for more information.

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