I've never had any real nutritional education. I took a class in college, and I vaguely remember learning a little about the "basic 4" food groups when I was in grade school. Neither of these classes went into any depth, but I did learn that food is comprised of macronutrients: protein, carbohydrate, and fats; and micronutrients: vitamins and minerals. I also learned that protein was very important, perhaps the most important macronutrient, and that protein should comprise the base of all our meals. Our proteins wear out regularly and must be replaced, and in order to do this, we must consume protein. Assuming I received a typical education, it's not surprising that the first question I hear when I mention I've gone vegan is "where do you get your protein?"
T. Colin Campbell, author of The China Study, calls protein "the most sacred of all nutrients." Indeed amino acids, which make up protein, are considered the building blocks of life. Eight of those amino acids are called the "essential" amino acids as we cannot make them ourselves, we need to ingest them.
Campbell goes on to discuss that idea of "quality" proteins, those proteins which provide the right kinds of amino acids in the right quantities needed to create the proteins required for us to survive. Apparently, human flesh is the most efficient food we can eat, in that it provides the correct amount of amino acids our bodies require. Since cannibalism is not something we typically engage in unless we've got some fava beans and a nice chianti (referencing The Silence of the Lambs), most of us look to animal flesh for our protein. Plant proteins make us work harder. We can get all eight of the essential amino acids by eating plant proteins, we just have to eat a variety of plants to do so. Extrapolating here... that means we could eat a steak and get what we need, or eat a variety of plants to get those same nutrients. When we had to work hard to get our food, it behooved us to eat meat if we could. But in today's era when food is readily available, and produce can always be gotten at the local grocery store, we can get the nutrients we need without consuming animal products. According to Dr. Campbell, "plant protein, which allows for slow but steady synthesis of new proteins, is the healthiest type of protein."
I've only started this book and have just gotten through the second chapter. You can read Skinny Bitchor take your cue from Oprah and read Quantum Wellness. Those books will give you the ethical and spiritual motivations to try or continue with a vegan diet. But if you want to understand the medical reasons to be vegan, you should probably read The China Study.
You can find links to additional nutritional information on our Resources page.