We now know that more than half of your body is not human! Human cells make up only 43% of the body’s total cell count. The rest make up the body’s microbiome and is made up of bacteria, viruses, fungi and archaea (similar to bacteria). This means that you’re more microbe than you are human.
The microbiome is a complex ecosystem composed of millions of organisms, found mainly but not exclusively in the gut. Science is discovering that it affects not just our gut health, but also our noses, throats, urinary tracts, genitals, and skin, and entire digestive system. Bacteria within the microbiome work with our bodies to help modulate immunity, protect us from toxins, better absorb foods, and fight disease.
One explanation of why the microbiome is so important to the human body could be the extra genetic material that it brings to the party. The human genome, the full set of instructions for a human being, is made up of 20,000 instructions called genes. But add all the genes in our microbiome together and the figure comes out at between 2 and 20 million microbial genes. And when you find out that a fruit fly has 14,000 genes, you conclude that our microbiome has a very important part to play for a human to function.
We haven’t always thought of bacteria as helpful, and when scientists discovered antibiotics in the 1930’s, they were used to save millions of lives by killing the bugs responsible for infectious diseases. But this assault on the bad guys has done untold damage on the good guys that live within the microbiome. And although the incidence of infectious disease has fallen dramatically, we have seen a rapid increase in autoimmune disease and allergy. Changes in the microbiome is being linked to a whole host of health conditions including obesity, inflammatory bowel disease, Parkinson’s disease, depression and autism.
Although the majority of the microbiome is found in the gut, it has a profound effect on the working of the brain, and vice-versa. Have you ever noticed how a ‘gut feeling’ can influence the decisions that you make? This is often referred to as the gut-brain axis, a two-way street between the central nervous system and the enteric (or gut) nervous system. It involves direct and indirect pathways between the cognitive and emotional centres of the brain with intestinal functions.
Through this link, the gut bacteria can help minimise the effects of stress, as they help produce mood-regulating neurotransmitters like serotonin that communicates with the brain. In turn, the brain signals the release of less cortisol, the stress hormone, helping us cope with mental turmoil.
The flipside of the coin is that consistent stress negatively effects the amount and diversity of your good gut bacteria. This can weaken the gut itself, making you more susceptible to inflammation, illness and nutritional deficiencies.
In order to look after your good microbes so that they can look after you, eat a wholefood diet with plenty of plant fibre, take a probiotic containing healthy live strains of bacteria and incorporate lifestyle stress reduction practices such as cutting down on stimulants like caffeine and alcohol, getting good sleep and practicing yoga or meditation.
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3 Carabotti, M. Scirocco, A. Maselli, M. et al. (2015) ‘The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems’ Annals of Gastroenterology 28(2):203-209.
4 Yano, J. Yu, K. Donaldson, G. et al. (2015) ‘Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis’ Cell 161(2):264-276.
5 Konturek, P. Brzozowski, T. & Konturek, S. (2011). ‘Stress and the gut: pathophysiology, clinical consequences, diagnostic approach and treatment options’ Journal of physiology and pharmacology’ 6:591-599.
6 Breit, S. Kupferberg, A. Rogler, G. et al. (2018) ‘Vagus nerve as a modulator of the brain-gut axis in psychiatric and inflammatory disorders’ Psychiatry 9(44).
