Demystifying the quantity:
Assuming your diet is not based on chips and soda, you can easily reach the minimum protein numbers that your body needs on a vegan diet.
Almost all foods contain protein, various fruits have protein, rice has protein, beans have protein (more than we need, actually), lettuce and cabbage have proteins, nuts, seeds, pasta, even white bread has more than only carbohydrates, has protein also.
Many people eat too much protein. The body has to process the excess, taxes the kidneys and cause kidney stones.
Too much protein can also kill. Watch this study (at 12 minutes):
Too much protein, especially from animal source, makes you lose calcium. When you eat meat your blood is acidic, and the body balances the pH of the blood by releasing a little calcium in the circulation, removing from the bones. Who eats too much meat needs more calcium than those who do not eat.
Regarding quality:
A protein is a set of amino acids. Any protein you eat is broken down into amino acids and then leave for their role in the body.
Frances Moore Lappe herself, who in 1971 wrote a book called Diet for a Small Planet, explained this misconception:
"In 1971 I said it was important to complement the protein, because I figured that was the only way to get complete proteins, based on similarity to animal protein. In combating the myth that meat is the only way to get high quality protein, I reinforced another myth. I gave the impression that to get enough protein without meat, considerable care was needed in choosing foods. Indeed, it is much easier than I thought. "
"With three major exceptions, there is little risk of protein deficiency on a diet of plant foods. The exceptions are diets very heavily dependent on fruit or on some tubers such as sweet potatoes or cassava, or junk food (refined flours, sugars and fats). Fortunately, relatively few people in the world trying to survive on diets in which these foods are virtually the only source of calories. In all other diets, if people are eating enough calories, they are virtually certain to get enough protein."
Source:
Said the responsible for the myth of protein itself!
There is another etymological confusion with the word protein, which comes from the Greek (of primary importance), and it seems that it is of ultimate importance. Now, everything is important. Carbohydrates, proteins and fats are important. Minerals and vitamins, fiber and water are important. I even worry at first take carbohydrates than protein. Of course, we're cutting too much here. We are reducing the food to vitamins and minerals, as if the multi-vitamins were all you needed to eat in your life. What is important are the foods you consume, not the nutrients. The orange, not vitamin C. The orange contains numerous other components that your body will use, numerous antioxidants, not only vitamin C.
"Let food be your medicine and not the medicine be your food." Hippocrates.
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Update:
The myth of the protein busted (in English):
