Fermented Foods and Gut Health

The gut microbiota is a hot topic at the moment. Supermarket shelves are lined with an ever increasing number of kombuchas, kimchis and other 'gut boosting, fermented superfoods' claiming to do all sorts of things for your health. There's no doubt that the foods we eat impact our health in numerous ways. But how can eating some soggy cabbage or plain old yoghurt improve our health? Let's find out.

What is the gut microbiota or microbiome?

You'll often hear the terms gut microbiota and gut microbiome used interchangeably, however there are slight differences between the two. The microbiota refers to the diverse community of bacteria, viruses, and other microbes that live in your gut while the microbiome encompasses all the genes of these microbes.

More interestingly, this community numbers approximately 100 trillion microbes! This mixture of microbes changes throughout your life and is influenced by all sorts of things including, you guessed it, diet [29899036].

How do these microbes affect my health?

Now, this is where the magic starts.. these living microbes are capable of using some of the food you eat to produce vitamins and many other compounds which can have positive or negative effects on your health, depending on the types of food eaten.

As we've been told countless times before, a diet rich in fatty, salty, sugary, or highly processed foods is not going to do wonders for your waistline. But it also impacts your gut microbes. Certain species thrive off these foods and produce compounds which promote inflammation and increase risk of developing diseases such as colon cancer, type 2 diabetes and cardiovascular disease.
The good news is that a switch to a healthy diet full of fibre rich vegetables, fruits, wholegrains, yoghurt, fish, and nuts can tip the balance of microbes in favour of the beneficial ones. These good bacteria produce compounds called short-chain fatty acids which not only keep our gut lining healthy and protect from pathogens but have also been shown to play a role in energy metabolism and appetite regulation. So, they can even trick you into thinking you're full! And if that wasn't convincing enough, all of these effects can contribute to lowering our risk of developing chronic diseases [28388917].


Where do fermented foods come into all this?

Now that you know just how special your gut is, don't you want to give it the care it deserves? Enter fermented foods. Fermented foods have been around since the ancient times and though some cultures have been lauding them for years, it's only now that we're seeing widespread recognition of their health benefits. They're created when microorganisms, either from the environment or commercially added, feed on or 'ferment' the raw food components to produce an end product with altered flavour, aroma, shelf life, composition and nutritional value [32184365].

You've probably eaten some fermented foods without even knowing it; they include foods like kimchi, miso, sauerkraut, kombucha, yoghurt, tempeh, and kefir to name a few. Even wine, beer, and cheese are fermented!
However, before you go indulging in all the wine and beer you like, I have to point out that other properties of these drinks, such as the sugar and alcohol, override any potential health benefits gained from fermentation.

How do they work?

Many fermented foods contain live microbes (probiotics) like the good ones living in your gut. If eaten in large enough quantities, these mix with your existing gut microbes to diversify the community and contribute to those beneficial health effects we discussed earlier.

On top of this, these foods also contain prebiotics which are essentially food for all these gut microbes to feast on and produce those short-chain fatty acids.
Various other products made by the microbes during the fermentation process can also interact with the gut microbiome and may confer health benefits [35406140].

Will kombucha make me super healthy then?

As exciting as all this sounds, health benefits vary depending on the fermentation techniques, raw food components, and microbial environment and there is still much more research to be done to understand the merits of each food. So I wouldn't be jumping on the "kombucha will change your life" bandwagon just yet.

In saying that, there is strong evidence associating regular consumption of fermented dairy products, like yoghurt and kefir, with reduced risk of cardiovascular disease and type 2 diabetes. Plant-based fermented foods, like kimchi, are also proving to be a worthwhile inclusion in your regular diet [32277831].

Foods to eat for a healthy gut:

  • Yoghurt
  • Kefir
  • Kimchi
  • Sauerkraut 
  • Fibre rich vegetables and fruits
  • Garlic, onion, leek
  • Wholegrains 
  • Legumes

Make sure you opt for the organic version where possible as the herbicides and pesticides used on non-organic produce (eg glyphosate) preferentially kill the good microbes. 


Written by
Alannah Mezzatesta, BSc
Nutrition Scientist (ANutr)
 last updated  27th July 2022