Any vegans here?

I have a doctor buddy (Dr. Heath Motley if you want to look him up) and he thinks vegan diets are counterproductive as the body requires certain proteins that are not available in non-meat foods. He is somewhat of a 'kook' in other theories but this one has medical backed data supporting his side. As in everything in life, eat a variety of foods in moderation. I eat 7-11 burritos 3X a week for lunch and I'm still healthy...shows what excercise can do outside of a diet. I walk about > 4000 steps a day, haul 80 lbs ladders and gaff poles all with a 25 lb tool belt on.