In the school we were taught that the human body needs many vitamins and mineral, that are found in different kinds of foods. They told us that if a human being doesn't receive them, he will die or at least get a serious disease, like bery bery. Our biology lessons had ugly pictures of people with enormous stomachs and unnatural appearences. "this one has a shortage of protein", "this one has a shortage of this or that vitamin" was written under those pictures.

  I am really confused. Since we know that in the past, many ascetics and monastic persons ate only bread and water with a little (if any) amount of fruits and vegetables, and none of them ended in looking like those freaky images or lose his eyesight due to shortage of vitamin A.
  In many countries people never used meat because in their false religion, killing an animal was sinful. Most people didn't have access to those kinds of fruits that didn't grow in their climate.
Did all of them look abnormal? Is science telling us lies?