There are six main vitamin groups that the human body needs for proper functioning. These are A, B, C, D, E and K. Out of these, A, D, E and K are fat-soluble, and are stored by the body to some extent in its fat reserves.
B and C, however, are water soluble and are excreted away as urine, when taken in excess. So these have more possibilities of being in deficit than the others.
Vitamin B is a family of substances grouped under the letter B that cause a number of significant body processes to go at a better pace and in a more orderly manner.