Nictrous is fine if spaced like 3 months between uses. Nitrous Oxide deactivates all b12 vitamins in your body basically as soon as you do it. b12 is necessary in order to maintain the health of your myelin sheaths which protect your nerves in your brain and spinal cord. Once your b12 is deactivated, using nitrous eats away at those sheaths and will eventually damage your nerves and you will see symptoms like lose of functionality in your extremities (toes, fingers, feet) and eventually it can get so bad that you cannot walk if you're using nitrous daily for weeks/months on end. Your body will replenish b12 vitamins but it takes MONTHS to do so naturally. Taking oral b12 vitamins after a nitrous sesh/weekend doesnt help a ton. liquid b12 injections are the only thing they're seeing working in the medical community right now ro reverse the demylenation.
Think of it like a video game where you have your Health bar and also an Armor bar. Doing nitrous will insantly deplete all your armor, any nitrous you do after that will begin to permanently hurt your health. So you need to allow your shield to recharge (take a 2-3 month break) after extensive seshes so that you're not slamming your nervous system that has experienced demylination:
https://my.clevelandclinic.org/health/diseases/demyelinating-disease