Vitamin C is an essential vitamin that must be consumed in the diet. Good sources include fresh fruits and vegetables, especially citrus fruits.

Vitamin C is needed for the body to develop and function properly. It plays an important role in immune function. Most experts recommend getting vitamin C from the diet rather than taking supplements. Fresh oranges and fresh-squeezed orange juice are good sources.

Historically, vitamin C was used for preventing and treating scurvy. Today, people most commonly use vitamin C for preventing and treating the common cold. It's also used for autism, breast cancer, heart disease and many other conditions.