I read today that our guts contain 1 - 2 kg of bacteria that are
our helpers to produce vitamin, break down food and so on.
Of course it is important to maintain a good balance of
the around 400 types. When we travel to another environment
it takes around a week to change the flora to suit the new food a.s.o.
The gut walls are renewed all the time, just as the skin. We loose
proteins equivalent to 200 grams of meat per day in this way.

- Hans