Vitamins are substances that are absolutely essential to ensure the smooth running of the body''s systems: immunity, brain, liver, blood cell formation, nervous sytem, you name it! Problems occur if there is a major lack of one or more vitamins, for example scurvy if vitamin C is deficient or beri-beri if vitamin B is lacking, osteopaenia (weak bones) with vitamin D deficiency. They are, however, only required in tiny quantities.