Vitamins and minerals in specified amounts are requirements to maintain a healthy body. The government also publishes guidelines outlining a minimum daily requirement for each vitamin and mineral. These guidelines are continually reviewed and updated. People who are nutritionally deficient certainly will benefit from dietary supplements or nutritional therapy. For example, the iron included in a daily multivitamin can make up for iron lost by menstruating women.
Pregnant women require more calcium, iron and folic acid than non-pregnant women.
Many people still are convinced that megadoses of vitamin C can cure colds, although many good scientific studies disproved that idea. On the other hand, the use of zinc lozenges, taken no more than one day after the onset of a cold, may be helpful in reducing the time the cold lasts and lessening its symptoms. Certain vitamins promote good eyesight, calcium helps build strong bones and teeth, and folic acid reduces the number of birth defects. The antioxidant vitamins, although still under study, seem to have real benefits in promoting good heart health. But there is no evidence that supplements cure or prevent cancer.