The human microbiome, which is comprised of all the microorganisms (the microbiota) that live on and in humans, plays an essential role in determining good health.
We are less than 1% human, if you factor in that more than 99% of the DNA contained within us belongs not to us, but to the microbes which we effectively host.
There is some confusion about the difference between pre- and probiotics. There are 400 – 500 types of bacteria in the digestive tract, each of which has many strains, with a total of one hundred trillion bacteria and a weight of about 2 kg (about the size of the liver). Just imagine the chaos created by a course of antibiotics!