Protein Energy Malnutrition

Protein-energy malnutrition (PEM) or, as it is still sometimes called, protein-calorie malnutrition (PCM), is a term of convenience that refers to a range of syndromes among infants and children of preschool age in whom manifestations of growth failure occur because of protein and energy deficiencies. In most instances this condition besets those in the less developed world of Asia, Africa, and Latin America, where dietary factors are thought to be a crucial part of the etiology. PEM thereby tends to exclude what is conventionally known as "failure to thrive" in Europe and North America, in which the vast majority of cases result from organic disorders such as cystic fibrosis or congenital heart disease problems and are not so directly associated with diet as such.

PEM is best described in its two clinical versions of kwashiorkor and marasmus. In the former, edema is always present, whereas extreme wasting (commonly defined as below 60 percent that of normal weight for height) identifies the latter. Much of the research in the 1950s and 1960s focused on differentiating between the symptoms and etiologies of kwashiorkor and marasmus, but since then it has become evident that cases purely of one or the other are the exception rather than the rule. The majority display both edema and extreme wasting, plus a variable mix of other symptoms, that have earned them the rather inelegant designation of marasmic kwashiorkor. In addition, far more common than all of the three put together are numerous subclinical syndromes, usually referred to as mild-to-moderate PEM. A frequent analogy for PEM, therefore, is an iceberg; only a very small proportion of the total is clearly visible. Most cases remain below the surface and go undetected except under close analysis.

Numerous attempts have been made to develop a logically ordered, comprehensive classification of PEM, but several problems have prevented the achievement of one that satisfies the demands of both clinicians and field workers. A particular dilemma is that the various syndromes are not static. Mild-to-moderate cases fluctuate considerably and can move in the direction of kwashiorkor, marasmus, or marasmic kwashiorkor in ways that remain unclear. Also, once established, the clinical conditions do not always stay constant until they are resolved. Kwashiorkor can become marasmus, and vice versa.

Another problem is what to measure, especially in the subclinical stages. Biochemical tests are expensive to perform, and in any event, they have not proved to be very reliable discriminators. As a result, anthropometric characteristics are relied upon. The simplest such indicator, and longest in use, is that of weight-for-age, a measurement that gives a reasonably good picture of current nutritional status, assuming, of course, that age is known accurately, which all too often is not the case. More critically, weight-for-age fails to differentiate between chronic and acute malnutrition. Because of these liabilities, the tendency today is to try to combine weight-for-height, which measures the degree of wasting, and thus the presence of acute malnutrition, with height-for-age, an indicator of stunting or chronic malnutrition. Other measures that have frequently been used in the field such as head and upper arm circumference and skin fold thicknesses add nothing to clarify the picture. They simply indicate if malnutrition is present but do not help in specifying the type.

Overriding the issue of anthropometric classification are the growth standards employed. Those in longest use were derived from studies of middle-class white Americans and are known as either the Harvard or Boston standards. More recently these have been superseded in international comparisons by those developed at the U.S. National Center for Health Statistics (USNCHS) based on a larger sample that cuts across ethnic and socioeconomic groupings. Most authorities tend to accept the position that with proper nourishment and general good health there are no significant human differences in infant and child growth patterns. However, some, especially in India, argue that there are differences, and that by using growth standards based on children of predominantly European ethnic backgrounds, a serious over-estimation of malnutrition in many other parts of the world results. In point of fact, the issue of differential growth is still unresolved. Until it is, the safest procedure is probably to accept the USNCHS standards, while remembering that these are designed for comparative purposes only and do not necessarily represent growth objectives that should be sought for each and every population.

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