wolfman1941
I have no idea where you're getting that information from. Every doctor I've ever talked to and every nutrition book I've read has said the exact opposite. The human body has a much easier time absorbing nutrients from plant based sources. Plant sources are much simpler than meat so the body has an easier time digesting and processing them, thus getting the nutrients from them quicker and easier. Protein, iron, and B-12 can all be obtained from other sources. Nuts and beans are excellent sources of protein. Broccoli and spinach are excellent sources of iron. B-12 is the only one that's a little tricky. You need supplements for that one OR fortified foods like fortified nut/soy/rice milks, cereals, nutritional yeast, etc.
Doctors are usually not informed on nutrition. It's why we have nutritionists. Most doctors I've had were qualified to deal with diseases, and prescribing medications. It may be different for your area, though.
Depends on the plant. Starchy items, like potatoes, carrots, etc... No problem. However, the insoluble fiber of most greens (lettuce, kale, broccoli, etc...) are near impossible to break down for the human body because of it's particular setup. It's hard to absorb stuff out of something when you have a hard time breaking it down. Just look at one of the common comments about corn is.
It is far easier for us to get our nutrition from plants by eating the animals that can properly break down those things (cows, deer, etc...) and eat them. Unfortunately, most of our critters are not raised to eat what they should be, and to make it worse, when's the last time most people you know ate something other than muscle meat? Organs, liver in particular, store a lot of really amazing nutrition, and it's pretty cheap too. Our store hardly sells them because they're not popular, at all.
That said, vegan can work. You just have to know your stuff. Some people screw it all up and end up getting sick or something, and blame the diet for it, when they should have gotten their facts straight beforehand.