What is Malnutrition?
Photo: Three sisters at a health centre in Haiti.
Malnutrition is usually the result of a combination of inadequate dietary intake and infection (Fig. 6). In children, malnutrition is synonymous with growth failure - malnourished children are shorter and lighter than they should be for their age. To get a measure of malnutrition in a population, young children can be weighed and measured and the results compared to those of a 'reference population' known to have grown well. Meas uring weight and height is the most common way of assessing malnutrition in populations.
Although many people still refer to growth failure as 'protein-energy malnutrition,' or PEM, it is now recognized that poor growth in children results not only from a deficiency of protein and energy but also from an inadequate intake of vital minerals (such as iron, zinc and iodine) and vitamins (such as vitamin A), and often essential fatty acids as well. These minerals are needed in tiny quantities, on the order of a few thousandths of a gram or less each day. They are con sequently called micronutrients. Mi cro nutrients are needed for the production of enzymes, hormones and other substances that are required to regulate biological pro cesses leading to growth, activity, development and the functioning of the immune and reproductive systems.
All of the minerals that the body needs - calcium, phosphorous, iron, zinc, iodine, sodium, potassium and magnesium, for example - have to come either from the food we eat or from supplements. While the body manufactures many of the complex organic molecules it needs from simpler building blocks, the vitamins - A, the B complex, C and so on - are not synthesized. Vitamin D is exceptional in that it can be made in the skin, providing a person has sufficient exposure to direct sunlight.
While micronutrients are needed at all ages, the effects of inadequate intake are particularly serious during periods of rapid growth, pregnancy, early childhood and lactation. We are learning more every day about the importance of micronutrients for the physical and the cognitive development of children.
While widespread moderate malnutrition may not be obvious unless children are weighed and measured, some severely malnourished children develop clinical signs that are easily observed - severe wasting (or marasmus) and the syndrome known as kwashiorkor, with skin and hair changes and swelling of arms and legs. Despite years of research, the reasons why some children develop kwashiorkor and why others develop marasmus remains a mystery. What is clear is that left untreated, children with either condition are at high risk of dying from severe malnutrition, and that both kwashiorkor and maras mus can be prevented by ensuring an adequate intake of nutritious food and freedom from repeated infections. Less severe forms of malnutrition also cause death, mostly because they weaken children's resistance to illness (Fig. 1).
The 1990 World Summit for Children singled out deficiencies of three micronutrients - iron, iodine, and vitamin A - as being particularly common and of special concern for children and women in developing countries. Recently, knowledge of the prevalence and importance of zinc for child growth and development has placed it in that league as well. Vitamin D deficiency is now recognized as a major problem of children in countries such as Mongolia, the northern parts of China and some of the countries of the Common wealth of Independent States that have long winters.
Throughout this report, the term malnutrition is used to refer to the con sequences of the combination of an inadequate intake of protein energy, micronutrients and frequent infections.
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