Abstract:
The final part of this series concludes the evaluation of the relationship between the human species and the human gut microbiome, focusing on whether their relationship is symbiotic, parasitic or somewhere in between. The possibilities based on animal studies are explored and compared to scientific facts proven in human beings. In particular, close attention is paid to the relationship between the gut microbiome and central nervous system, and the effect of this on human behaviour. This relationship is termed the 'microbiome-gut-brain axis'. The gut microbiome has an influence on stress (both acute and chronic), anxiety, loneliness and depression, as well as odour and attraction, through a number of pathways. It has also been associated with the development of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and with associated cognitive decline. It has also been postulated to play a role in schizophrenia. Since the common treatments used for these conditions are not equally effective in all patients, it is vital for clinicians to explore other avenues to be used as therapeutic targets. The gut microbiome, in particular, requires further research in order to aid the development of future therapies for certain conditions. The role of vitamin D in relation to the gut microbiome and the brain, and the impact of the gut microbiome on autoimmunity and systemic disease and how this affects the brain is explored. Randomised controlled trials in human beings are greatly needed to prove or disprove the effects of the gut microbiome on complex psychiatric diseases.
