Imagine a living being whose gastrointestinal tract alone contains 100 000 billion bacteria from over 500 bacterial species, secretes at least 20 neurotransmitters and produces 70-85% of their immune cells.(1)
Imagination is not required – that being is you, your family, your friends, your clients, your patients – a single human being.
We have evolved into superorganisms whose gastrointestinal tract has its own immense microbial community of bacteria viruses, fungi and many more- the gut microbiota – and with our cells estimated to be 10% human, 90% bacteria, we are more bacteria than human.(2)
Additionally, the microbial community in the human large intestine (colon) has the greatest number of microbes, ‘…and represents the most densely populated and biodiverse ecosystem on earth.’(3)
Sharing a symbiotic relationship with this vast community is critical for human function. For so long though we have known little about the world within us and the effect it has on our health and wellbeing. Fortunately, research methods are developing rapidly and with new technology we have identified, characterised, established functions and discovered new links between many body organs and systems and the gut, including the nervous system and the brain.
The human microbiota has now become so important with its wide range of functions that researchers are calling it the ‘forgotten organ’.(4)
This hidden population exists for our survival, but we are blissfully unaware of their activities and the benefits they provide every second of the day. Understanding the bacteria that predominate in the gut and their importance means we can nurture, heal and promote their growth and survival for our own beneficial gains.

Microbiota – What are the Features and Benefits for Us?

The role these organisms play in our health is increasing with greater research. To date it is known that they have far reaching functions, such as;
• Energy Production/Metabolism
• Digestion support and function
• Gut wall health- required for gut function and to inhibit unwanted substances, such as large proteins, from entering the bloodstream and initiating allergies and autoimmunity.
• Immune system function, development and cellular communication
• Anti-inflammatory promotion
• Nervous system function, development and neural communication
• Production of neurotransmitters and neuromodulators- needed for cellular communication to assist in healthy emotions, good sleep-wake cycles and organ function.
• Neuroendocrine function- balancing the production of hormones through communication with the nervous system.
• Nutrient production (e.g. arginine, glutamine, vitamin K, folic acid and vitamin B12)
• Bone health
• Prevention of growth and survival of pathogens (disease- causing microbes).(5)

But, what does this mean to us, as humans going about our day to day lives?
Many of us suffer from frequent colds, lethargy, moodiness, depression, anxiety, insomnia, hyperactivity and inflammatory conditions. Our first thought for treatment options of these, often chronic conditions, may be focused on the respiratory system, the nervous system or the skeletal system.
However, these conditions may be linked to a disturbed microbiota, commonly termed dysbiosis.
Dysbiosis- The Inner War
Intestinal dysbiosis is often described as a state in which the ‘good bacteria’ are unable to control the ‘bad bacteria’. (6)
But it goes further than that. Often the ‘bad bacteria’ are not introduced into the gut through food or water but may be normal residents of the microbiota who have grown, changed or seized an opportunity to become a potential pathogen.
It is also not limited to bacteria – candida is one such opportunist.
Candida is a fungus that normally resides in the gut microbiota, it is harmless – when it is kept at a manageable level by other microbes, such as bacteria. However, candida being a very virulent and adaptable organism, can take the opportunity to thrive when it lacks competition. This can occur in situations such as antibiotic use, when a number of bacteria are destroyed, or in individuals with chronic illness or lowered immunity.
This changes the gut microbiota from normal to dysbiotic. (7)
An overgrowth of candida can produce a myriad of symptoms with the most common being thrush (oral and vaginal). But literature and clinical anecdotes also relate candida infection to brain fog, behavioural problems and learning disabilities. (8)

The Systemic Links Cannot Be Ignored

‘Intestinal dysbiosis has been linked with important human diseases, including autoimmune and/or autoinflammatory disorders, such as IBD, metabolic disorders, such as, obesity, type 2 diabetes, allergies, and neurological disorders.’ (6)
With 75-80% of immune cells in the gut we cannot ignore the potential role of the gut bacteria in any immune dysfunction or autoimmune condition.
Research has even identified a gut-brain connection, termed the brain-gut axis. Studies have shown that the gut microbiota has a two-way communication with the brain, influencing emotions, pain perception, sensation and behaviour.(9, 10) Therefore, we simply cannot ignore the potential of gut health for neurological conditions and brain health.(9)
In fact, researchers are already studying beneficial organisms (probiotics) to treat conditions, such as depression, anxiety and other psychiatric illnesses- they are called psychobiotics.(11) These may change the face of psychiatric medicine, provided treatment protocols take into account the complex individuality of human beings.

Individualised Gut Bacteria

The microbiota is so unique to each individual that it has even been referred to as our gut ‘fingerprint’.(5) It is agreed that a check list for a healthy microbiota composition is yet to be discovered because of its individuality to each of us.(9)
But where did this uniqueness begin?
The initial establishment of our gut ‘fingerprint’ begins at birth or during gestation.
Many authors state that the gastrointestinal tract of a foetus is sterile; however, later research has shown there may be some bacterial transfer from the mother to the child during the pregnancy.(12) Either way, the main establishment of our microbiota begins with colonisation from the mother in vaginal births and from the immediate environmental exposure, such as the mother’s skin and the hospital environment, for babies born by caesarean.(3) Therefore, the type of delivery has a major impact on the initial colonisation. Interestingly, research has stated that caesarean births are linked to a modest increased risk of autism spectrum disorders.(13)
Over the first 2-3 years from birth the microbiota changes until, as an infant, they have developed an adult like composition- their own little gut fingerprint. Up until then many factors, such as gestational age, diet (breast milk vs formula), solid food introduction and exposure to antibiotics, can also affect the composition. (5)
With ongoing investigation it appears that the microbiota of the gut environment is affected by many situations we come across in our daily lives. The degree to which some of these factors affect the long term stability of our unique microbiota is not fully known; however, it seems we have some power in changing our own composition, adversely and beneficially.

Part Two: Do we have the Power to Change Our Unique Gut Microbiota? – What affect do lifestyle, diet and antibiotics have on these old friends? Can a simple diet change alter the unique composition?

References

1. Delcenserie V, Martel D, Lamoureux M, Amiot J, Boutin Y, Roy D. Immunomodulatory effects of probiotics in the intestinal tract. Curr Issues Mol Biol. 2008;10(1-2):37-54.
2. Autoimmunity Research F. Microbes in the human body 2014. Available from: http://mpkb.org/home/pathogenesis/microbiota.
3. Quercia S, Candela M, Giuliani C, Turroni S, Luiselli D, Rampelli S, et al. From lifetime to evolution: timescales of human gut microbiota adaptation. Frontiers in microbiology. 2014;5:587.
4. Clemente JC, Ursell LK, Parfrey LW, Knight R. The impact of the gut microbiota on human health: an integrative view. Cell. 2012;148(6):1258-70.
5. Quigley EMM. Gut bacteria in health and disease. Gastroenterology & hepatology. 2013;9(9):560-9.
6. Schippa S, Conte MP. Dysbiotic Events in Gut Microbiota: Impact on Human Health. Nutrients. 2014 Jan;6(12):5786–805.
7. Mayer FL, Wilson D, Hube B. Candida albicans pathogenicity mechanisms. Virulence. 2013 Feb 15;4(2):119–28.
8. Vogan SBT-TL. Miracles Can Happen: An Interview with Warren M. Levin, MD, FAAFP, FACN, FAAEM. 2013 Feb 1;(364)
9. Aziz Q, Doré J, Emmanuel A, Guarner F, Quigley EMM. Gut microbiota and gastrointestinal health: current concepts and future directions. Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society. 2013;25(1):4-15.
10. Tillisch K, Labus J, Kilpatrick L, Jiang Z, Stains J, Ebrat B, et al. Consumption of fermented milk product with probiotic modulates brain activity. Gastroenterology. 2013;144(7):1394-401, 401.e1-4.
11. Dinan TG, Stanton C, Cryan JF. Psychobiotics: a novel class of psychotropic. Biological psychiatry. 2013;74(10):720-6.
12. Reid G, Brigidi P, Burton JP, Contractor N, Duncan S, Fargier E, et al. Microbes Central to Human Reproduction. American journal of reproductive immunology (New York, NY : 1989). 2014.
13. Curran EA, O’Neill SM, Cryan JF, Kenny LC, Dinan TG, Khashan AS, et al. Research Review: Birth by caesarean section and development of autism spectrum disorder and attention-deficit/hyperactivity disorder: a systematic review and meta-analysis. Journal of child psychology and psychiatry, and allied disciplines. 2014.
14. Sommer F, Bäckhed F. The gut microbiota–masters of host development and physiology. Nature reviews Microbiology. 2013;11(4):227-38.