Vitamin C (or as it is known by its more technical term, ascorbic acid) that is essential to all of life. Vitamin C is an important factor in many of the body's various life-giving and life-maintaining functions including the successful operation of the immune system.

Unfortunately, Vitamin C is not water soluble (meaning it cannot be saved in the body's fat content for later) and it is not something that the body naturally produces.
This means that although it is an essential vitamin, it must be replenished every day in order for good health to be maintained. There is at least some vitamin C content in all fruits and vegetables though one particular type of fruit that seems to have a higher concentration is fruit in the citrus family.

The orange is most closely associated with Vitamin C for this reason.
Directions
As a dietary supplement, take 1-2 tabs daily or as directed by a physician. Individual preferences vary.