Have you ever been annoyed by a clumsy customer who walks on your feet and claws at you à la Dracula as he gropes for his seat in your row at the movies? Count ten before you slap him down for rudeness; he may be a victim of avitaminosis A (fancy language for lack of Vitamin A).
Maybe you yourself hate to drive a car at night because approaching headlights dazzle you. Maybe you find it difficult to read or thread a needle in dim light. One of the earliest signs of Vitamin A deficiency is a characteristic form of night blindness that makes it difficult to see after dark.
The next time you go to a movie, give yourself a slow count of twenty when you get inside the darkened theater. If you are not then able to see well enough to find a seat under your own optical power, you may suspect that your liver is running short of Vitamin A.
A large cross-country trucking company adopted the custom of feeding its drivers raw carrots (containing Vitamin A in its plant form) at the beginning of their night hauls. What happened? The number of night accidents was significantly reduced.