Vitamin B1, B3, B6 and B12 contribute to normal energy-yielding metabolism, to normal functioning of the nervous system and to normal psychological function. Vitamins B2, B3, B5, B6, B9 and B12 also help to reduce tiredness. Vitamins B2, B6 and B12 play a role in maintaining normal red blood cells. Vitamin B5 contributes to a normal metabolism of some neurotransmitters. Vitamin B6 helps to regulate hormonal activity and the normal functioning of the immune system and helps the body to metabolise protein and glycogen normally.