Like many aspects of life that we're all trying to grapple with, good health comes from a very fine balance. There is no 'one way' to do things, but a sweet spot in the middle.
And I believe it's the same with diet, in particular B12.
B12 is a regulator of homocysteine. Low B12 is a driver for high homocysteine, which is a driver for CVD and heart problems.
However, methionine is also a driver for high homocysteine. But methionine is found in meat, with higher levels coming from higher amounts of meat.
So basically, if you don't eat meat you'll increase homocysteine. And if you do eat meat you'll also increase homocysteine.
"Excess dietary methionine and B vitamin deficiency can elevate plasma homocysteine, and B vitamin supplementation can lower plasma homocysteine levels."
ncbi.nlm.nih.gov/pmc/articl...
draxe.com/health/homocystei...
So are vegans who supplement with sufficient B12 doing it right? Lowering CVD rates with plant-based nutrition? Or are meat-eaters fine and just need to avoid eating burgers and steaks everyday?
There is no straight answer. It's just that nature has created a bizarre paradox for us, like most of life, that there is no black and white. There is only somewhere in the middle.