The way that we conceptualize the many foreign microbial bodies that thrive in our own systems has shifted in a dramatic way. Starting at birth and throughout adulthood, the human body is a welcoming host to thriving microscopic life.
In fact, the total number of foreign microbial cells in the human body is roughly equivalent to the number of human cells. The human body is like any other ecosystem – the survival of one species is dependent upon the functions of many others.
The variety foreign microbial cells throughout our bodies serve to maintain healthy daily processes and a growing body of evidence suggests that they play a major role in our moods and cognitive processes.
Diverse species of bacteria, fungi and yeast reside on every square centimeter of skin exposed to the outside world. Every crevice and fold of our skin are tiny habitats that foster the life of bacteria like staph and streptococcus, surviving symbiotically by producing antimicrobial substances that ward off more pathogenic invaders.
Internally, the bacteria that occupy the lower parts of our gastrointestinal tracts aid in digestion. These bacteria live in us and work for us every day recycling waste and protecting delicate tissue that could easy be overtaken by microbes with more malicious intent.
These microbes also work on our behalf beyond local symbiosis, elicitingwidespread influences on human health and behavior. The development of immunity, metabolism and body type, and even cognitive development and functioning have all been linked to relative health of bacteria in the GI tract.
Elegant animal studies have highlighted these relationships, which has since spurred a wave of funding by groups like the National Institute of Health (NIH), giving millions of dollars to the studying the “mind-gut-brain” axis.
Despite the growing research initiative, illuminating a causal link that microbiota are responsible for other realms of human health has been challenging, as many of the relationships between gut health and overall well being are not immediately evident.