This is not a comment on what to put in or take out of the review, it's just a bunch of stuff I know at least something about.
There was a guy in my residential college when I was in university who didn't eat any animal products at all for religious reasons. And he was ripped. As in I looked like a stick figure next to him. So that's filed under anecdotal person I know. His brother was more like me and relatively skinnier but still also much more built than me. So that's two anecdotal people I know (he didn't eat any animal products either.)
You can get Vitamin B12 in your diet naturally. Even as a complete non-meat eater, it takes years to develop clinically even if you stop consuming any.
Here's some options:
1,2 and 4 are obviously out for vegans (I don't know what the hell 3 is supposed to be - it scares me just a bit, actually.)
Now 5, we grew up on that stuff, or more accurately its related cousin Vegemite (Marmite's a bit different in taste and the UK variant.) So we can eat that stuff by the truckload in Australia but I guess it's an acquired taste, it tends to repel all other humans.
Interestingly enough, your body does produce Vitamin B12 but it's at a point below the stomach. This is because parietal cells in the stomach produce intrinsic factor which the Vitamin B12 needs to bind to in order for your gut to be able to absorb it.
I'm guessing in the far past, this wasn't an issue but due to evolution, the system's now been rendered non-functional like this probably because our diets changed so much at some point and we ate enough Vitamin B12 - so maybe when meat eating started?
Actually, that's another good point. When you see advertisements use the terms "essential vitamins", that's a redundancy of expression. By definition, a vitamin is "any of a group of organic compounds which are essential for normal growth and nutrition and are required in small quantities in the diet because they cannot be synthesized by the body." - admittedly Vitamin D complicates this picture a bit but that's a story for another day (or at least another post.)
I mean the other thing is, a large part of the world doesn't get meat in their diet because they can't acquire it. Cost of production (to produce 1kg of meat needs many kg of grain and lots of water - other resources, time and space needed not practical for the opportunity cost etc) and cost of acquisition is just out of their reach. But it doesn't mean these people are malnourished. Believe it or not, insects are one part of a lot of people's diet in parts of the world and there's quite a selection to choose from.
Basically large parts of the world don't eat meat but they're not vegans either because they eat all sorts of things we've never heard of, let alone things we have but never thought of eating. I guess there's both a lot of Western-centric positions both with being pro and anti vegan in terms of the discussion of it.
I'm not sure where all of this that I've just said would go in relation to the review because I need to study and research the subject more. This is just a bunch of stuff I know at the moment which I hope can help with further discussion of this topic and maybe it's a springboard to bringing other things that might be of value to integrate into the review.
For example, maybe a mention of vegetarianism versus veganism (the Buddhist monk whose 100th birthday ceremony at the old Sri Lankan parliament building (conveniently near our house) I went to was in excellent shape and didn't even need a walking stick - in fact generally they all do pretty good, could be a place to start.
Also, I did see an anecdotal story of someone who used to taunt vegans who smoked with the fact they test cigarettes on animals. This could we worth further investigation (in a general sense, trying to avoid all things that have animal products somewhere or were tested on animals is nigh on impossible.)
Anyway, this is all something we should at least look at, it could be a fun trip with an interesting and unexpected destination like the time I finally thought I should look into what the point of white people was but like I said, that's a story for another day or at least post.