I now get a chance to use my biology class that I was able to get instituted in college. The course did not require any animals being dissected. It was completely on nutrition. Anyway here goes.
The human body needs 12 essential amino acids. A vegan diet only gives you eight of those. So it looks like we are in trouble. Now for the good news. The other four are synsitized by the other eight. That is backed by scientific proof. Please feel free to check it out by using solid scientific organizations.
There is only one thing that we need that is not provided with a vegan diet. That is vitimin B-12. We must get that with a supplement.
I have been a vegetarian for 44 years and the last 15 years has been as a vegan. I receive regular physicals and blood tests. I am 70 years old and I have been in excellent health for a man my age. Since I have had two leaky heart valves from childhood, I have had several tests with cardiologists. They have all found my arteries are whistle clean. Each of them said that the vegan diet is the best diet for heart problems. Without a vegan diet I would have mechanical heart valves by now.
Also it has been shown that vegans and vegetarians live at least five years longer on average than with non-veg'ns.