The classification of vitamins is based upon their activity-the chemical and biological functions that each is involved with within the human body. Therefore, a "vitamin" classification may well refer to a series of "vitamer" compounds, each of which is related by the work it undertakes. For example, "B-12" refers to several vitamers, which are the chemical compounds that exhibit the "B-12" vitamin activity.
The body is unable to produce sufficient quantities of vitamins, yet these organic compounds are required for a range of biochemical functions. Metabolism, the process by which food is converted into energy for use within the body, is dependent on the B group vitamins, as coenzymes, which act as catalysts or subtrates, (molecules acted upon by enzymes). Others act as antioxidants, ( for example, vitamin E), helping to rid cells of free radicals; as hormones, regulating specific processes; or by affecting tissue and cell growth, (such as vitamin A).
The human body must ingest vitamins in order to function optimally. Conveniently, the advent of synthetically-produced vitamins in the last century, has removed the need to locate and ingest the necessary levels through the food eaten. Supplementation inexpensively allows for the rectification of deficiencies in the quality or quantity of these nutrients obtained in the diet,and ensures optimal levels are mantained.