B12 is the only real deficiency vegans experience and it's easily solved by taking a supplement. B12 isn't some miracle vitamin, exclusive to animal products either. It's produced by bacteria in the soil and since we're usually sterilizing our food, it's not usually found on our produce anymore. That's why livestock are getting it supplemented, just the way vegans are supplementing it. It's not even like eating meat and animal products saves you from B12 deficiency as a big chunk of the population is actually deficient.
https://nutritionfacts.org/video/the-protein-combining-myth/
B12 is the only real deficiency vegans experience and it's easily solved by taking a supplement. B12 isn't some miracle vitamin, exclusive to animal products either. It's produced by bacteria in the soil and since we're usually sterilizing our food, it's not usually found on our produce anymore. That's why livestock are getting it supplemented, just the way vegans are supplementing it. It's not even like eating meat and animal products saves you from B12 deficiency as a big chunk of the population is actually deficient.