From the earliest hours of life and onward, the human microbiome is in constant flux with microbial cells lurking within the body, (39 trillion) outnumbering human cells (30 trillion). A recent book review from Adrian Woolfson in Nature highlights how the human microbiome influences our overall health and wellbeing.1
As Woolfson explains, the microbiome begins to take shape during infancy. Human breast milk contains indigestible oligosaccharides, which are taken up by gut bacteria such as Bifidobacterium longum infantis. This bacterium releases short-chain fatty acids that influence the permeability of an infant’s gut cells, which is thought to help build up the immune system.
As we age, an imbalance of gut microbes can be a source of disease. Because the microbiome is so essential to health, some suggest that the human microbiome should be viewed as a distributed organ performing fundamental functions akin to those of our liver, lungs or kidneys. Alteration to bacterial communities cause abnormalities in internal microbial ecology which can be a cause of obesity. Interestingly, Ed Yong’s book, Contain Multitudes, explains that obese individuals have more bacteria from the phylum Firmicutes and fewer from the genus Bacteroides and a relative lack of Akkermansia muciniphila compared with individuals at a healthy weight. In 2013, an experiment with obese mice determined that transplanting microbes from lean mice can make obese mice lose weight. What’s more, in The Mind–Gut Connection, Emeran Mayer explains that early programming errors in the putative brain–gut–microbiome axis can result in medical conditions that might benefit from treatment with probiotics. Remedying the disruptions in the microbiome could help with chronic pain disorders and irritable bowel syndrome
Also an important player in neurologic function, the microbiome affects our emotions through the neurologic connections between the gut and the nervous system. In her book, This Is Your Brain on Parasites, Kathleen McAuliffe contends that our resident microbes act like puppet masters, manipulating how we think, feel and act. To learn more about connections between gut microbes and the brain, check out this article on Microbes and the Mind.
Woolfson predicts that in the future, microbiome profiling will be as routine as blood testing as agencies such as the US Human Microbiome Project and National Microbiome Initiative work to unlock the complexities that surround the human microbiome.
Adrian Woolfson (2016) “Microbiology: Mob rule” Nature 536 (pp. 146–147) 11 August 2016 doi:10.1038/536146a Published online 10 August