About vitaminsvitamins are substances that are found in foods we eat. the term vitamin is derived from the words vital and amine, because vitamins are required for life and were originally thought to be amines. all vitamins are not amines. vitamins are different in their chemistry, but they all are organic nutrients that are necessary in small amounts for normal metabolism and good health. most vitamins must be provided by the diet or by supplements- only three vitamins (d, k, and the b vitamin biotin) can be manufactured in the body from non dietary sources. vitamins are not sources of energy as are carbohydrates, fats, and proteins. instead, vitamins serve as chemical partners for the enzymes involved in the body`s metabolism, cell production, tissue repair, and other vital processes. vitamins serve crucial functions in almost all bodily processes example immune, hormonal and nervous systems. in humans there are thirteen vitamins, divided into two groups.