Traditional fermented foods such as pickled vegetables, kimchi, fermented milk products, kefir, and fermented soy products are rich in beneficial lactic acid-producing bacteria. These bacteria are what naturally make milk products go sour and cause vegetables to ferment. In the gut, these bacteria help ferment carbohydrates that we, as human beings, cannot digest properly. The by-products from this process help keep an acidic pH in the gut, which prevents harmful organisms from being able to grow while good gut bacteria colonise and populate.

One of the key claims for the health benefits of fermented foods is their contribution of live microbes – also known as “good” bacteria – to the existing colonies in the gut. Collectively called the microbiome, these microbes exert powerful effects on our bodies by creating a protective lining in the intestines, protecting us against pathogenic factors and bacteria such as E. coli and yeast overgrowth. As a result, this improves digestion, helps protect against inflammation, oxidative stress and disease, and enhances immune function.


Describe a ‘healthy gut’ – what sorts of bacteria would be present?

While there is no standard definition, A “healthy gut” is seen as a general absence of disease or gastrointestinal issues. Other people recognise a healthy gut from a functional perspective, which optimal digestion, absorption and assimilation of food occurs. However, five criteria have been set to provide a positive basis for understanding a healthy gut:

  1. Specific Signs of Gastrointestinal (GI) Health
  • Normal nutritional status and effective absorption of food, water, and minerals
  • Regular bowel movement, normal transit time, and no abdominal pain
  • Normal stool consistency and rare nausea, vomiting, diarrhoea, constipation, and bloating
  1. Absence of GI Illness
  • No acid peptic disease, gastroesophageal reflux disease, or other gastric inflammatory disease
  • No enzyme deficiencies or carbohydrate intolerance
  • No inflammatory bowel disease, coeliac disease, or other inflammatory state
  • No colorectal or other GI cancer
  1. Normal and Stable Intestinal Microbiota
  • No bacterial overgrowth
  • Normal composition and vitality of the gut microbiome
  • No GI infections or antibiotic-associated diarrhoea
  1. Effective Immune Status
  • Effective GI barrier function, normal mucus production, and no enhanced bacterial translocation
  • Normal levels of immunoglobulin A, normal numbers and normal activity of immune cells
  • Immune tolerance and no allergy or mucosal hypersensitivity
  1. Status of Wellbeing
  • Normal quality of life
  • Qi (ch’i), or positive gut feeling
  • Balanced serotonin production and normal function of the enteric nervous system

When talking about a healthy gut, you can’t go past the importance of bacteria. But for you to be healthy, these bacteria must be in balance. Too many of the wrong bugs, like parasites, yeasts and bad bacteria — or not enough of the good bugs like lactobacillusor bifidobacteria– can seriously damage your health. The bacterial inhabitants of the human gastrointestinal tract constitute a complex ecosystem. More than 400 bacterial species have been identified in the faeces of a single person and reside in different areas of the gut. The upper gastrointestinal tract (the stomach, duodenum, jejunum, and upper ileum) normally contains less microflora and pass through the gut with each meal. In contrast, the large intestine normally contains a majority and vast amount of microflora.



How does a healthy gut affect our overall health and wellbeing? What does it contribute to?


Hippocrates once quoted “all disease begins in the gut.” Time is proving Hippocrates to be pretty spot on, and science is even now linking poor gut health with a myriad of health problems. While each of us has a unique microbiota (similar to individual finger prints), it always fulfils the same physiological functions, with direct impact on our health. Some of the functions include:

  • It helps the body to digest certain foods that the stomach and small intestine have not been able to digest.
  • It helps with the production of some vitamins (B and K).
  • It helps produce hormones that assist with the storage of fats.
  • It helps protect against pathogenic (bad) bacteria and yeast that are ingested.
  • It plays an important role in stimulating and activating the immune system.
  • A healthy and balanced gut microbiota is key to ensuring proper digestive functioning.

Taking into account the major role gut microbiota plays in the normal functioning of the body and the different functions it accomplishes, researches are now seeing a link to poor gut health and certain health conditions and disease. Some of these include:


  • Inflammatory bowel disease (IBD) – Crohn’s disease, ulcerative colitis
  • Irritable bowel disease (IBS)
  • Coeliac disease
  • Obesity
  • Metabolic syndrome
  • Inflammatory joint disease
  • Eczema, atopic dermatitis
  • Psoriatic arthritis
  • Food allergy
  • Urinary tract infections (UTIs)
  • Asthma
  • Endometriosis
  • Chronic heart failure
  • Chronic fatigue syndrome
  • Psychological conditions
  • Autism spectrum disorder



How do bad bacteria thrive?


It’s important to note that even though bacteria such as Escherichia coli (E coli) or Staphylococcus (staph) have been labelled as “bad” bacteria, we live with these bacteria every day in our gut and on our skin.  Not all bacteria are either inherently bad or good. The problem lies when our body is out of balance, the bad bacteria take advantage of the opportunity and proliferate and over populate, potentially causing harm to our bodies.


“Bad” bacteria are traditionally defined as pathogenic bacteria, which means they may cause infection, make us sick or, in some cases, even kill us!  Bad bacteria come from external influences such as food (sugary and refined foods), environmental toxins and even the effects of stress on our bodies. These foods and environments feed pathogenic microorganisms such as yeasts and other bad bacteria in the gut, which allows them to grow and overpopulate to unhealthy levels causing adverse symptoms such as bloating, abdominal pain/discomfort, diarrhoea, constipation, gas, belching and reflux.


What sorts of things can negatively affect gut health (e.g. poor diet, antibiotics)?


Sometimes a disturbance in the force, or an imbalance in the homeostasis of our bodies, will turn a healthy gut microbe into a colony of very unfriendly bacteria inside our bodies. There are many other factors that negatively affect our gut health and these include:


  • Antibiotics and other medications such as anti-inflammatories
  • Recreational drugs
  • Genetics
  • Smoking
  • Alcohol
  • Poor diet – high fat, high sugar, low fibre, fast food
  • Stress
  • Vitamin D deficiency
  • Food intolerance
  • Artificial sweeteners
  • Refined and processed sugars
  • Heavy metal exposure/toxicity
  • Hormone imbalances
  • Preservatives, additives, herbicides, pesticides
  • Caffeine
  • Hygiene practices
  • Mode of delivery (birth)
  • Type of feeding as an infant i.e. breast milk versus formula
  • Environment
  • Recurring infections
  • Depression/anxiety
  • Disturbed sleep patterns


How do fermented foods and a healthy gut help prevent weight gain?


Emerging research over the years has shown that gut bacteria alter the way we store fat, how we balance levels of glucose in the blood, regulate metabolism and how we respond to hormones that make us feel hungry or full – all of which influence weight. The wrong mix of microbes, it seems, can lead to obesity and diabetes from the moment of birth. One possible mechanism for how changes in the gut flora cause “diabesity” (a form of diabetes which typically develops in later life and is associated with being obese) is that different species of bacteria seem to have different effects on appetite and metabolism. It seems that too much bad bacteria in the gut may contribute to an increase in appetite and as a result, consume more food and calories. Furthermore, this may contribute to an altered metabolism.


Other studies have shown that changes in the gut flora can increase the rate at which we absorb fatty acids and carbohydrates, and increase the storage of calories as fat. This means that someone with bad gut flora could eat the same amount of food as someone with a healthy gut, but extract more calories from it and gain more weight.

The interaction between diet and gut bacteria can predispose us to obesity from the day we are born, as can the mode by which we enter the world. Studies have shown that both formula-fed babies and infants delivered by caesarean section have a higher risk for obesity and diabetes than those who are breast-fed or delivered vaginally. This is because the vaginal lining contains a significant number of healthy bacteria and the same for breast milk.


Therefore, by consuming fermented foods and increasing the number of healthy bacteria in the gut, you will increase your chance of achieving optimal gut health and may reduce your risk of becoming obese and suffering metabolic dysfunction.



In a nutshell, how is consuming fermented foods linked to our mental health?



The gut and brain have a profound ability to influence each other. This bi-directional interaction occurs via multiple mechanisms including neurotransmitter activity, neuroendocrine and immune influences. Addressing any disruptions in these communication pathways provides beneficial health outcomes, particularly for mental health.


In a nutshell, any inflammation such as free radical damage in the body can significantly influence neurological health. When the gut becomes inflamed, there is an increase in intestinal hyperpermeability, and as a result there is often an increased passage of lipopolysccharides (LPS), toxins and other potentially harmful molecules into the body.


These trigger an inflammatory immune response, contributing to oxidative stress and neuroendocrine imbalances. If not corrected, the inflamed gut results in chronic activation of the inflammatory response in which inflammatory cytokines can access the brain and exert multiple negative influences on brain and mood health.


The above processes can be minimised or avoided if we increase the number of healthy bacteria in the gut. Therefore, by consuming fermented foods and/or probiotics, you are able to achieve this. Two strains of probiotics shown to have a calming influence on mood, by dampening stress hormones, are Lactobacillus helveticus andBifidobacterium longum.

These bacteria are capable of producing and delivering neuroactive substances such as gamma-aminobutyric acid (GABA) and serotonin, which act on the brain-gut axis.




How do gut microbiota influence our brains?


I think I answered this above, but have added some more:


As mentioned earlier, gastrointestinal integrity is important for preventing complications of inflammation on the central nervous system. We have learnt by now that the microbiome plays a significant role in maintenance of gut barrier integrity. Furthermore, specific bacterial species have the ability to produce, or restrict the production, of a range of neurotransmitters e.g. GABA and serotonin that are vital for optimal mood and brain health. Research has shown that specific bacterial species can have short term influences on anxiety behaviour and increase the expression of certain neurotransmitter receptors (e.g. GABA), which help to calm the stress response.


A healthy balance of microbes in the gut has been shown to beneficially influence and support brain health. On the other hand, inflammation and local infection due to bad bacterial overgrowth is shown to contribute to anxiety-like and depressive symptoms. Plus, emotional stress can alter microbial colonies, contribute to IBS-related symptoms and result in loss of intestinal integrity, demonstrating that gut-brain influences are a two-way street.


Finally, friendly gut microbes have also been shown to support local detoxification processes, preventing the uptake and aiding the removal of toxins such as heavy metals. Minimising the exposure to toxins helps to protect against the neurological damage these substances may cause.



When adding fermented foods to our diet, should we be taking it slowly?

If you aren’t used to consuming these foods, you may have to work them into your diet gradually. The reason being is that too large a portion may provoke a ‘die off’ reaction to the sudden dose of probiotics, which occurs when the probiotics kill off pathogens (bad bacteria) in your gut. When these pathogens die, they release toxins and as a result may experience symptoms such as cramping, bloating, gas and even diarrhoea. Therefore, if you are new to fermented foods, you should introduce them gradually, beginning with as little as one teaspoon ofsauerkraut with a meal. Observe your reactions for a couple of days before proceeding with another small portion, and increase your dose gradually, as tolerated by you.


At the supermarket, what words should we be looking for on packaging to ensure we’re getting the most benefit (eg live cultures)?

When looking for the best fermented food products on the supermarket shelf, make sure the they fulfil the following criteria:

  • They should be in a glass jar.
  • All products must be ‘raw’ and this should be stated on the label.
  • The product must not contain vinegar or sugar.
  • The ingredients should be ‘unpasteurised’. This may or may not be on the label.
  • Buy organic – Look for fermented foods that are made from the best raw materials possible, namely those made from organic, non-GM or locally farmed produce. Look for the Australian Certified Organic stamp/label.
  • Some labels might mention ‘probiotic-rich’ or ‘packed with good bacteria’.
  • Fermented foods should be found in the refrigerator section of the health food store or supermarket to keep the temperature stable and good bacteria (probiotics) alive.
  • Other words that you might find on the label include: ‘naturally occurring probiotics’, ‘naturally fermented’.