Do people need nitrogen from air for health?
No. This is well established!
Can people breath totally nitrogen-free atmosphere for a long time?
Yes. Also well established!
I know, nitrogen is essential for life, and in big quantities, but
maybe people can take it entirely from food, from proteins, etc?
As expounded on in the comments by AliceD, nitrogen ...
The gut microbiome is partly to blame, at least for the associations of red meat consumption with heart disease. Red meat has a high concentration of L-carnitine, which is metabolized by bacteria in the gut to produce trimethylamine, which is further metabolized by FMO3 in the liver to produce trimethylamine-N-oxide (TMAO). High blood levels of TMAO are ...