Thank you for your comment @yagoub! :)

The amount of protein in plant products is not that high as in animal products. But you have to keep in mind that a normal human only needs 0.8 grams of protein per kilogram of bodyweight per day. This is not that difficult to achieve on a vegan or vegetarian diet. Many people underestimate the amount of protein in plant products. If you add up the protein amount for every food you eat in a day, you will see that it is possible. A vegan diet needs knowledge and planning as I said. On that condition, there is no reason to be afraid of any lack of protein in a vegan diet.

You are right with that. Asians that migrated to America show taller and bigger offsprings. According to scientists, nutrition and other factors of environment could be the cause of this.