The vitamin B-complex refers to all of the known essential water soluble vitamins except for vitamin C.Each member of the B-complex has a unique structure and performs unique functions in the human body. Vitamin B1, B2, B3 and biotin participate in different aspects of energy production, vitamin B6 is essential for amino acid metabolism, and vitamin B12 and folic acid facilitate steps required for cell division. Each of these vitamins has many additional functions.contributes to normal energy-yielding metabolismthe reduction of tiredness and fatiguethe normal metabolism of ironthe maintenance of normal red blood cellsnormal functioning of the nervous system (size R)