Getting to the guts of the matter

The ‘gut’, is the gastrointestinal tract – the tube that food goes in, and eventually comes out. It includes your small intestine, large intestine and colon. The gut microbiome, however, is what most of the recent fuss is about. The gut microbiome is the population of literally trillions of tiny creatures living in your gut RIGHT NOW. In total, these little critters weigh a kilogram and while there are multiple types of microbiota in the human gut, we are dominated by the Bacteroidetes and the Firmicutes. It is the delicate balance of these bacterium that can determine ‘good’ or ‘poor’ health. Thanks in large part to the Human Microbiome Project; we know that gut health is linked with gastrointestinal diseases like irritable bowel syndrome, metabolic diseases such as diabetes, obesity and cancer. There is even some evidence for a relationship between gut microbiota and autism spectrum disorder (ASD), largely supported by studies findings improvements in symptoms as a result of treatment with both probiotics and antibiotics. If you are anything like me, you may have long suspected that your ‘real’ brain lies in your stomach. You will be pleased to know that science supports the idea of the gut as the body’s second brain, via the gut-brain-axis. The gut is controlled by the enteric nervous system (ENS), which communicates directly with the central nervous system (CNS; the brain and spinal cord). The gut is home to neurotransmitters like serotonin that in fluence our mood and wellbeing, and sensations produced by the ENS lead to some of the recognisable signs of stress or emotional turmoil, obvious examples being ‘butter flies in the stomach’ and ‘gut feelings’. So, can we improve our gut health? Well, your unique microbiome ngerprint is determined in the first years of life. In fact, more than 99 percent of your genetic information is microbial, making us more ‘host’ than ‘human’. As we move from the germ-free womb into the brave new postwomb world, we are ‘colonised’ by an army of microorganisms. The first evidence of this is that babies born via vaginal delivery show a similar gut microbiota pro file to the vaginal microbiota of their mother. After our first few years of life, the demographics of our microbial population are stabilised and our immune system has developed. To a great extent, the microbiome that we have at this point is the one we will have forever. While the balance of bacteria in the gut changes naturally with age, diet and health status, the obvious rst step to optimise gut health is to maintain a healthy diet – that means avoiding fast foods and ramping up consumption of high- fibre foods, root vegetables and nuts. A more extreme option being explored is ‘faecal transplants’. This involves transplanting the microbiota from a healthy person, into the gut of sick person. And yes, this is exactly what it sounds like and is not to be attempted at home. This method has been e ffective for treating an antibiotic resistant pathogen (a bacterial bad guy, in this case C. Di fficile) responsible for the death of 14,000 Americans per year. Probiotic use has also had positive results, and is perhaps a more palatable option. Probiotics stimulate the natural immune system, and inhibit the growth of various pathogens. The strongest evidence for probiotics is their usefulness for treating and preventing gastrointestinal upsets like rotavirus diarrhoea or antibiotic associated diarrhoea. Before I sign o ff it seems important to note that, like all scienti c advances and on-trend health issues, any information about the gut and the gut microbiome, should be taken with a grain of salt. In his recent paper in Nature journal, Harvard A/Professor of Epidemiology William Hanage warns against getting carried away by scienti fic advances in this area. As Hanage advises, “Whenever a study links a microbiome to a disease, wise critics should ask whether other contributors to disease are considered, compared, and reported”. Similarly, while recent advances are telling us that alterations in the makeup of the microbiome are linked to certain illnesses, it is not necessarily clear whether these alterations cause the illness, or the illness causes the alterations. While a little cynicism goes a long way when deciding which quasi-scienti fic taglines you’ll swallow and which you should investigate further, there is good reason to believe that gut health contributes to overall health. But how it contributes, and what you can do to optimise this contribution, remains to be seen. Dr Jessica L Paterson is Research Fellow at the Appleton Institute, CQUniversity