The Human Ecosystem

The Human Ecosystem

‘The answer lies in the soil’

Recently, I re-jigged my vegetable patch, which had been neglected and slowly had become overgrown with weeds. While I was still learning the tricks my mother taught me, she always insisted that it was the quality of the soil that determined the health of the plants that grew in it. “Get the soil right,” she would tell me, “and you’ll reap the rewards of a healthy, robust garden strong enough to resist an attack.”

As a Nutritionist, I’m now able to see the strong link between the garden my mother created and the human ecosystem, of which one key part is the gut microbiota or microbiome, more commonly known as intestinal flora. ‘Microbiota’ refers to the community of microbes and then their collective genome is referred to as the ‘microbiome’. 

When it comes to the human body, it’s the microbiota that provides a foundation for a healthy body.  It consists of an extraordinarily large and diverse community of microorganisms; bacteria, yeast, fungi, viruses and more. These are both beneficial and pathogenic (disease causing) and predominantly reside within your large intestine. Every person has their very own unique microbiome, which can harbour up to 150 different species of bacteria and can weigh up to two kilograms. 

When balanced, our gut bacteria contributes positively to our digestive function by breaking down nutrients, producing some of the B vitamins as well as vitamin K, and playing a role in gut motility. 

When balanced, our beneficial bacteria acts as a physical barrier, creating a defence army against invading, enemy pathogens. If this balance swings the other way however (dysbiosis), opportunity will arise for pathogenic microbes to contribute to inflammation, digestive disturbances, immune dysfunction and the progression of other chronic diseases. Around 70% of our immune system is formed within the gut, so when our gut health goes south, so too does our immune health. 

The microbiota also communicates with our central nervous system, influencing our brain chemistry. One example is that the vast majority of serotonin, our neurotransmitter responsible for making us feel good, is synthesised within our gut. This is a two-way relationship, known as the ‘gut-brain-axis’. The condition of our microbiota can therefore influence the way we think and feel - and the way we think and feel can influence our microbiota. A growing body of research continues to lay down the link between the microbiota and conditions such as autism and depression. 

From the minute we enter this world, whether it is via a vaginal birth or a cesarean section, the foundations of our microbiota are being influenced and our so-called blueprint begins to form. The first few years of life are absolutely critical in the initial seeding and from that point onwards it is our behaviour and lifestyle choices that dictate the health or otherwise of our ever growing and changing microbiota. 

A substance that creates major shifts in gut microbial composition is antibiotics. Australia has one of the highest usages of antibiotics in the world, which have a much-needed place in medicine, however, it is the misuse or overuse of these substances that can create serious problems for our health. Antibiotics effectively work on bacterial infections, but not viral infections, and it is important to understand that some more than others can tend to work like a blunt instrument, killing off beneficial bacteria in the process of eliminating the bad. When we knock out the good guys there is more room for the bad guys to move in - set up camp, play loud music, get drunk, have a party and leave the house in a mess. 

Now if we go back to the garden, the biggest single influence on the health of the plants is the condition of the soil in which they sit. Likewise, one of the biggest influences on human health, over which we have some control, is the microbiota. It becomes a continuous relationship of tending to our garden, providing enough ‘fertiliser’ (nutrients), to promote growth, as well as the development and maintenance of our good bacteria. It is then that we can reap the benefits of these microscopic and rather incredible organisms. 

A call to action!

  • Prebiotics provide nourishment for the beneficial bacteria and are the best way to influence the quantity and diversity of beneficial microbes. Prebiotics are non-digestible fibres such as inulin, resistant starch, beta-glucans and pectin and include some of the following foods; leek, onion, garlic, asparagus, green bananas and blueberries. 
  • Probiotics are live organisms provided by supplementation or fermented food sources such as unpasteurised sauerkraut, kefir, beet kvass and kombucha. 
  • A diet high in refined carbohydrates, sugars and processed foods literally starves the beneficial bacteria and negatively impacts the gut microbiota.  
  • Sterile environments early on in life have shown to decrease an individual’s diversity in their microbiota. 


Biasucci, G. et al. (2008). Cesarean Delivery May Affect the Early Biodiversity of Intestinal Bacteria. The Journal of Nutrition, 138(9). Retrieved from: http://jn.nutrition.org/content/138/9/1796S.long 

Department of Health (2015). The Pharmaceutical Benefits Scheme. Retrieved from http://www.pbs.gov.au/info/industry/listing/participants/public-release-docs/antibiotics-oct-14-feb-15

Reardon, S. (2014). Gut-Brain link grabs neuroscientists. Nature, 515. Retrieved from: http://www.nature.com/news/gut-brain-link-grabs-neuroscientists-1.16316 

Rodríguez, J. M. et al. (2015). The composition of the gut microbiota throughout life, with an emphasis on early life. Microbial ecology in health and disease, 26. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315782/ 

Hoban, E, A. et al. (2016). Regulation of prefrontal cortex myelination by the microbiota. Translational Psychiatry, 6. Retrieved from: http://www.nature.com/tp/journal/v6/n4/full/tp201642a.html