Animal protein is very acidic, and disease thrives in acidic conditions. (Google Alkaline diet - or I think I saw a forum for it here somewhere). I made the choice to be vegetarian at 13 and all was well until some years later I developed anaemia. My doctor basically told me I would continue to get sicker and sicker unless I started to eat meat again. And I, not being well enough informed about nutrition and being afraid to disobey the mighty medical establishment.... started to eat meat again. It never sat well with me, always freaked me out (i hated the smell of it and handling it raw) but I believed it was for the good of my health. And from that day I suffered depression, anger, apathy and a litany of ailments too long to go into. I am a very creative person and quite spiritual, but during the time I was eating meat this all left me. All my interest in the things I used to feel passionate about and really stand up for seemed to fade and instead life was a struggle. Then I started to study nutrition and holistic health, and found out that you do NOT need animal products to live and that I was right, they cause putrefaction and disease in the body, so I gave up meat again. And now I feel like I'm 18 again. No, 13. Words cannot describe it, I just feel so much more like myself. Now this might seem a little far fetched, and it is just my own personal experience, I guess what I'm trying to say is I think it's much easier to stay well without the burden of all that acid forming indigestible protein. A serving of beans with brown rice will provide all of the essential amino acids and in a much more usable form than in a piece of meat (don't forget how much energy the body will have to expend trying to digest a piece of meat - energy much better spent on healing and getting well). Spirulina & Chlorella are high in protein. And there are some really convincing meat substitutes on the market made from concentrated vegetable protein that look, taste and smell just like meat(I fool my son with them all the time lol!!).
Best of luck