Vitamin B is a water-soluble vitamin. Water-soluble vitamins are those that dissolve in water and are easily absorbed into the bloodstream during digestion. They are not stored in the body to any significant extent, and any excess amounts are excreted in the urine. This means that water-soluble vitamins need to be consumed regularly in the diet to avoid deficiency. Vitamin B is actually a complex of eight different B vitamins, all of which are water-soluble. Some of the important functions of the B vitamins include helping to convert food into energy, supporting healthy skin and hair, and aiding in the formation of red blood cells.