There are fourteen worldwide-recognized vitamins, most of which can neither be synthesized nor stored. They must be ingested from food except few that can be synthesized in the body or produced by intestinal bacteria, and stored in the body. Under normal diet, vitamin deficiency rarely occurs. But lack of vitamins in food, vitamin intake deficiency due to certain diseases, vitamin malabsorption, increased requirements of vitamin in body, or even decreased vitamin synthesis in consequence of interference effects of some medicines, can lead to vitamin deficiency.
Mineral system maintains inorganic compounds indispensable for human nutrition and body functions. And some minerals may cooperate with certain vitamins in a synergy. The required amount of some minerals, such as calcium, potassium, phosphorus, sodium, chlorine and magnesium, which account for a large proportion in human tissues, is quite large. Some require a relatively small amount with a very small proportion of body weight, such as iron, zinc, selenium, manganese, iodine and copper, are known as trace elements, which are yet essential to human body.
