> The commenter I responded to said that people don't need to eat animal products to live at optimal health, which is laughable
That is still technically incorrect and is refuted by observing healthy old vegans that consume supplements from cultivated-bacteria only for decades.
Those bacteria also develop in some animals digestive system as you already know, and eating those animals has been for a long time our main source of b12. The other (minor but non trivial) one has been non-washed fruits and plants human consumed during millennia, and that’s still how grazing animals ingest a bit everyday. The non grazing animals are widely supplemented with cultivated-b12. We’re producing around 80T/year for that which isn’t much we animals only need around 10mg/year. I'm not discussing the "non-natural" qualification of supplementation, just the fact it's today a very white practice to live an healthy (human or non human animal) life by ingesting only bacteria sourced B12.
> we've cracked the code on the "essential" nutrients
That is still technically incorrect and is refuted by observing healthy old vegans that consume supplements from cultivated-bacteria only for decades.
Those bacteria also develop in some animals digestive system as you already know, and eating those animals has been for a long time our main source of b12. The other (minor but non trivial) one has been non-washed fruits and plants human consumed during millennia, and that’s still how grazing animals ingest a bit everyday. The non grazing animals are widely supplemented with cultivated-b12. We’re producing around 80T/year for that which isn’t much we animals only need around 10mg/year. I'm not discussing the "non-natural" qualification of supplementation, just the fact it's today a very white practice to live an healthy (human or non human animal) life by ingesting only bacteria sourced B12.
> we've cracked the code on the "essential" nutrients
Yes we did, and the last of that nutrient has precisely been vitamin b12 which led to two Nobel prizes : https://pubmed.ncbi.nlm.nih.gov/23183296/