Surprisingly, even though I eat no meat, and little egg, my vitamin B12 was fine when they last tested it.
I've rarely ate meat in my entire life. When I was about 15 months, I suddenly stopped eating all healthy foods, and was eating only bread, yoghurt, and similar foods. I eventually started eating fruits, and recently I've started eating vegetables. It is because of my SPD that i can't enjoy many foods, because either the textures or flavours are a bit overwhelming. For example, cheese, I hate it for both reasons. I've tried it time and time again, nope, still not nice. Carrots, I like it, but when swallowing, the texture is terrible and sometimes triggers my gag reflex. Not fun. Same is true with a lot of veggies.
I never really liked meat, and I never enjoyed the idea of eating an animal. I remember once while at Mauritius in 2018, my brother jokingly said, "I know why she doesn't eat meat! She's vegetarian!" Me not knowing what it was at the time, took it seriously and told my parents "I'm no longer eating meat because I'm vegetarian." Now they can't force me to eat it LOL. I remember trying chicken schnitzel once a long time ago, and it wasn't that bad. And one time I was forced to eat a piece of cooked chicken(which tasted terrible) because I spat out some veggies... my parents would never do that again, they really just had a hard time getting me to eat healthy because of my sensory issues. Now I can eat whatever I want, which include relatively healthy foods.
Sorry Ollie if I hijacked your thread a bit, I just wanted to share my experience being vegetarian