Our digestive tract contains trillions of bacteria encompassing thousands of different species that collectively make up the gut microbiome. In fact, the number of bacterial cells that have colonized our bodies outnumbers the human cells that make up our bodies by a factor of ten to one, and the majority of those bacteria reside in our gut! These little passengers aren’t just along for the ride, and you could say that we’ve entered into a mutually beneficial contract with them; they enjoy a place to call home and a constant supply of food, while we benefit from their ability to break down our food into vital nutrients.
It turns out, however, that the gut microbiome plays an even larger role than helping us digest our food, and many of our body’s biological functions – from our metabolic processes to our immune system – are exquisitely sensitive to changes in the composition of the bacteria that reside in our gut. Disruption of this delicate balance has been implicated in a host of health conditions such as diabetes, obesity and autoimmune diseases like inflammatory bowel disorder and multiple sclerosis. I will return to the link between the gut microbiome and MS in a moment.
The microbial ecosystem in our guts is shaped by the various exposures that we come across in life, such as the food we eat, the air we breathe, any infections we’ve acquired or drugs we’ve taken, along with a host of other environmental factors. These environmental exposures interact with our body’s own physiological processes, such as metabolism and stress, to further alter the balance of our microbial communities. There’s even evidence to suggest that our genes have a hand in influencing the composition and abundance of the gut microbiome, and that these “heritable” strains of bacteria are associated with health and disease. What this means is that each individual’s gut microbiome is unique, acting as a microbial “fingerprint” that carries the potential in the future to help predict risk of various diseases or offer new therapeutic targets.