There absolutely isn't a scientific consensus. If anything, several cases have come up recently to counter the wild acceptance that anyone can live vegan just fine, and further investigation is still necessary. Just recently, the carnivore diet has taken off for multiple people, and even just significantly reducing plant-based foods in favor of animal-based foods is showing to help many people. There's also the theory of anti-nutrients and the importance of genetics which we still don't understand.

If there is one field that's an absolute mess, its nutritional sciences. The only thing one can trust is their own experience with any particular diet, their overall well-being and regular health check-ups. What works for one person can be absolutely disastrous for another.

Our livestock is given chemically manufactured b12 supplements because the soil is being depleted of the microbiology that produces and leaves it on plant material which is the natural way to get it. So everyone, including meat eaters are consumers of b12 supplements, unless they live in regions where modern agriculture does not have a strong foothold.

Similarly, modern western foods is full of supplements via “fortification” so to say that vegan diet is unnatural because of the need for supplements is a mute argument, so long as those supplements are part of everyone’s diet, and meat is just a carrier.

My point is still that the debate over plant based diets are too simplistic and based on anecdotes (on both sides). If we spent all the tax money we now spend on meat and dairy subsidies instead on unbiased research and education on general nutrition, I am convinced a lot of people would be surprised at the outcome.

The only supplements in our household are b12 and vitamin D. B12 is a supplement in everyone’s diet in the western world already, as I have argued, and vitamin D is universally recommended supplement in the northern region anyway due to lack of sun exposure in winter. Instead of getting it through fortified milk or fish oil, we take a pill, and we feel a lot better about it.

>> There absolutely isn't a scientific consensus. If anything, several cases have come up recently to counter the wild acceptance that anyone can live vegan just fine, and further investigation is still necessary.

Please note I didn't comment that "anyone can live vegan just fine".

Well to address the point you are making about poor people. Looking at the current poor population of North America, the cheap meat based diet is nothing short of a disaster to general public health ridden with all sorts of dietary caused diseases such as obesity, diabetes, coronary diseases and so on. Surely, a shift towards plant based diets for this demographic couldn’t make things any worse than it already is.

My understanding about the problem with the diet of "the current poor population of North America" is not so much that they don't eat enough plant food, but that they eat all kinds of over-processed food, full of saturated fats, sugars and salt, and that any kind of food they get, meat or plant-based is of poor quality. Removing meat from that diet, even the poor quality meats they can afford right now, sounds like it would hurt their diet even more, not improve it.

I don’t think there is any evidence to support that claim.