The Importance of Fermented Foods + Gut Health

5min read

The gut is often referred to as a foundation pillar of our health as our digestive system is connected to the entire bodies health requirements from the gut brain axis, to skin health, immunity, hormones and even liver detoxification.

When accessing gut health, nutritional therapy is particularly concerned with:

  • The health of the gut lining (preventing or repairing leaky gut);
  • The body’s ability to produce stomach acid and digestive enzymes so that we can assimilate food;
  • The levels of secretory IgA (a first line of antibody defence);
  • The gut ecology and microbiome.
  • Supporting immunity – 70% of our immune system is located in our gut
  • Supporting mood – 90% of serotonin (a neurotransmitter required to uplift the mood) is produced in our gut

Gut Flora

It is gut ecology and particularly gut bacteria that have predominantly been in the spotlight in recent years. Beneficial bacteria have been linked to weight loss, allergy reduction, mood, skin issues and many more complaints. Sales of live native bacterial probiotics have rocketed, but so too has interest in ‘fermented foods’ – foods that contain, and have been transformed by, live beneficial bacteria.

Many fermented foods contain 1 million to 1 billion viable microbes per gram or millilitre, and a large portion of those survive passage through the digestive tract, so eating fermented foods could increase the number of microbes in the diet by up to 10,000-fold. While these microbes may play only a transient role in an individual's native microbiota, they still have demonstrated benefits, including benefits for brain and immune function.

Organisms in kombucha, sauerkraut, kimchi, tempeh, and other fermented foods are often closely related, even to the species level, to organisms that have been reported to have probiotic functions. For example, one of the most abundant organisms in sauerkraut and kimchi is Lactobacillus plantarum. One particular strain called L plantarum 299v, is a very well-studied probiotic that is added to a range of commercial foods and supplements. However one common myth about fermented foods is that they're the same thing as probiotics. The World Health Organization defines probiotics as live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host. To be a probiotic food, a fermented food must retain an adequate level of live microbes that have been shown to have a health benefit. Not all fermented foods reach that bar. But that doesn’t mean they don’t have amazing gut health benefits nonetheless.

Fermentation itself is an ancient process, preceding human history, that can be both a science and an art, and can even occur in the cells of our bodies. It is the transformative action of microorganisms (bacteria or yeasts) as well as the enzymes they produce. Fermented foods are a collaboration with microbes;  via the bacterial (or yeast) conversion of sugar and starch to acids and other by-products, including ethanol. The acidity not only prevents growth of food spoilage bacteria, but the fermentation process has been used as a food preservation method for thousands of years whilst simultaneously creating foods with unique sour, tangy flavours.

My favourite fermented products that I use daily and make myself include sauerkraut (‘sour cabbage’) from Germany, kombucha originally from China, kimchi from Korea and water kefir from the Caucasian mountains. Other yummy fermented goodies I recommend to my clients include miso, tempeh from Club Cultured and even pickled dill cucumbers.

Products that are subsequently processed by heat, baking or filtration (e.g. pasteurised sauerkraut, sourdough) inactivate or remove the microbes in fermented foods, and so will not contain live cultures. Always look for “raw” or “live” products when purchasing or better still learn how to make your own. Its super easy and as always anything made by your own hand will be much more filled with love and goodness.

The bacteria that we mainly want to encourage into our products in order to access their health benefits are lactic acid bacteria, also known as or lactobacilli or ‘LAB’. The term lacto-fermentation is also used to describe the work they do. These bacteria are found on all plants but in relatively low numbers due to other types of bacteria dominating in the natural environment. Fermenting the food means eradicating the other types of bacteria and allowing the lactobacilli to thrive.

As the LAB transform their ingredients they produce nutritional benefits. Phytate bonds are broken away making the minerals more accessible, proteins are taken apart into peptides and amino acids, reducing their allergenic potential. It is as though the ingredients were pre-digested for us! B vitamins can be increased (B1, B2 and B3 in particular) and anti nutrients or toxins such as nitrates and also oxalates, related to kidney stones, are removed.
Fermentation of fibre-rich foods can also produce novel bioactive compounds that may have benefits for immunity, glycaemic response, and reducing inflammatory states such as:

  • Increasing the bioavailability of nutrients, eg B vitamins, magnesium, zinc
  • Converting unsaturated fatty acids such as linoleic and linolenic acids to conjugated linoleic acid, which has anti-inflammatory and antioxidant properties
  • Improving the polyphenol and vitamin content and reduce the amount of caffeine in tea eg in kombucha
  • Removing/reducing toxic or antinutrients in raw foods, such as phytic acid
  • Producing a form of the neurotransmitter GABA that may help reduce anxiety
  • Creating the female hormonal benefiting phytoestrogenic isoflavones:  genistein and daidzein out of their precursors in soyfoods eg in tempeh

    As you can see fermentation is an incredible art with some amazing nutritional benefits. If you’d like to find out more about how you can make fermented goodies at home then you can buy my online fermentation course with video demonstrations to teach you how to make kombucha, water kefir and sauerkraut along with my fermentation e-book with full instructions.


    Healthy Mays is a registered nutritionist and certified yoga, breathwork and meditation teacher. I work with clients to help them achieve their health goals via 1-1 nutrition support and I have been featured in publications such as Women’s Health, Health & Wellbeing and Bella.

    Get in touch with Mays via or Instagram: @healthymays.

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