A well-balanced diet should contain adequate amounts of all vitamins and minerals required for health. For most people, supplements are unnecessary, and high doses may even be harmful. However, certain groups of people are vulnerable to vitamin or mineral deficiencies. Doctors may prescribe vitamin or mineral supplements for people in these groups to prevent a deficiency or to treat a deficiency that has already developed.
Groups who are particularly prone to developing vitamin and mineral deficiencies include young children, pregnant women, and elderly people, especially those who live alone. Those who are seriously ill due to injury or long-term illness, or those who have disorders that impair their ability to absorb nutrients from the digestive tract (see Malabsorption), are also at increased risk of deficiencies, not only of vitamins and minerals but also of other nutrients (see Nutritional deficiencies). These people may require dietary supplementation with extra proteins, carbohydrates, and fats as well as vitamins and minerals. In the case of individuals who are unable to eat and drink normally because of illness, such as a stroke, which prevents them from swallowing, nutrients sometimes have to be given in a liquid form by tube, either through the nose down to the stomach or directly into the stomach. More rarely, for example in people who have very severe intestinal disorders, nutrients may be administered directly into the bloodstream through a vein.
The body needs some nutrients, such as carbohydrates, proteins, and fats, in relatively large quantities but requires vitamins and minerals in only small amounts. The articles in this section describe the vitamins and minerals that doctors most commonly prescribe as dietary supplements. The first article deals with vitamins and the second with minerals.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.