B12 is the only thing, and we can buy food that reinforced with it so no big deal. Many cereals have it added, and this can not be overstated, it’s the only thing that is problematic for vegans naturally. I’m not even a vegan, but B12 is added to all sorts of foods these days.
Also if that’s the case, then eating meat is class warfare. While people are starving, we are growing food to feed to live stock, to get a food people think tastes better. For every 1000 calories of food fed to cattle, you’ll get less than 100 calories of meat. There is not enough land on the planet for every person to eat meat the way folks in the US do.
globalagriculture.org/…/meat-and-animal-feed.html…. "Nearly 60% of the world’s agricultural land is used for beef production, yet beef accounts for less than 2% of the calories that are consumed throughout the world. "
That 60% is counting all the corn and soy agriculture that is fed straight to beef. The world is not big enough for humans to eat as much as meat as people do. As a delicacy? Sure. But eating it every day? Multiple meals? Part of the world will always starve if we do. There is nothing in meat that we can’t get in other ways, not a single thing. So in all honesty if we want a stable world, we will need to figure out our addiction to meat.