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MALNUTRITION: PROTEIN ENERGY MALNUTRITION

evidence of clinical malnutrition who have low weight- for-age should not be classified as malnourished; doing so may not only misdiagnose an individual, but may over- estimate the prevalence of malnutrition in a population. Also, the Gomez classification has been criticized because a single measure of a child’s weight referred to age gives no idea about the nutritional history of the child. That is, an underweight child may be growing according to his/her normal growth channel, may be recovering from a recent episode of weight loss (“catch-up growth”), or may be deteriorating in relation to the recent past.

In order to overcome these caveats, Waterlow pro- posed combining weight-for-height, as an indicator of an acute episode of malnutrition, with height-for-age, as an indicator of chronic nutritional deficits that would be re- flected in growth stunting (Waterlow, 1972).

Although these classifications have been used for sev- eral years, they have two important disadvantages that of- ten are overlooked. To illustrate the first disadvantage, it is important to highlight the concept of Z-scores as a means of describing an individual child’s anthropometric indicators in a normal distribution. The normal distrib- ution of a reference population has been published by the World Health Organization (WHO) and is most often accepted worldwide as the standard for comparison. Eighty percent of the median weight-for-age might be above or below 2 Z-scores, depending on the child’s age. The second disadvantage is that, to approximate a fixed point in the normal distribution, say, 2 Z-score, different percents of median have to be used depending on the anthropometric index used—for example, 90 per- cent for low height-for-age, or 80 percent of low weight- for-height.

In consequence, the World Health Organization Ex- pert Committee on Physical Status has recommended the use of Z-scores to express weight-for-age, weight-for- height, or height-for-age relative to values reported in a reference population (WHO Expert Committee on Phys- ical Status, 1995). The use of this system has several ad- vantages; i.e., when applied at a population level, it allows the mean and standard deviation to be calculated for a group of Z-scores, and it allows the use of fixed cut-off points (i.e., 1, 2, or 3 Z-scores) to classify mild, moderate, or severe deficits for any anthropometric in- dicator. Although the use of Z-scores may be difficult to grasp for those who have been accustomed to classifying nutritional deficits based on the percent of median, the advantages of Z-scores outweigh their disadvantages.

Global Prevalence of Protein-Energy Malnutrition

The most recent estimates about the distribution of PEM at a worldwide level were compiled by the World Health Organization (WHO) Programme of Nutrition, available in its Global Database on Child Growth and Malnutri- tion (de Onis and Blössner, 1997). This database covered 95 percent of the total population of children under 5 years of age who lived in 103 developing nations in 1995,

ENCYCLOPEDIA OF FOOD AND CULTURE

as was reported in nationally representative surveys avail- able at the time. According to these data, an estimated 206.2 million children, who represent 38 percent of all children under 5 years old, were stunted (low height-for- age); 167.3 million children (31 percent) were under- weight (low weight-for-age), and 48.8 million children (9 percent) were wasted (low weight-for-height). PEM is most often found in the poor regions known as the “de- veloping world.” The largest number of affected children were found in Asia, where 41 percent of all under 5 years old were stunted, 35 percent were underweight, and 10.3 percent were wasted. Africa had 38.6 percent stunted, 28.4 percent underweight, and 8 percent wasted children of all those under 5 years old; Latin America and the Caribbean showed 17.9 percent stunted, 9.5 percent un- derweight, and 3 percent wasted children of all those un- der 5 years old. The proportion of children under 5 years of age affected in Oceania was 31.4 percent, 22.8 percent, and 5 percent, respectively, but the total number of chil- dren living in this region is much lower, so in reality, these percentages translate into many fewer children af- fected than in the other regions.

Since the mid-1980s, the Administrative Committee on Coordination/Sub-Committee on Nutrition (ACC/ SCN) of the United Nations periodically has examined the trends of malnutrition in the world’s children. In its Third Report on the World Nutrition Situation (ACC/ SCN, 1997), this Committee (from data from 61 coun- tries) estimated the trends in stunting with two or more nationally representative surveys. In the period from 1980 to 1995, stunting declined globally at a rate of 0.54 per- centage points per year. Sub-Saharan Africa had an in- crease of 0.130 percentage points per year in the average prevalence of stunting; the remaining regions of the world showed statistically significant decreases that ranged from 0.26 in Middle-America and the Carib- bean to 0.90 in Southeast Asia (Table 1).

The same Committee was able to use data from 95 countries that had data from at least one national survey to estimate the prevalence of undernutrition; under- weight and stunting showed a consistent 11.5 percentage point difference. The higher prevalence was for the un- derweight classification. During the 1980–1995 period studied, only sub-Saharan Africa had an increase in the prevalences of both stunting and underweight; all the other regions showed decreasing trends in these two in- dicators (Table 1).

Acute and Long-Term Consequences of Protein-Energy Malnutrition

PEM results from a relative deficiency of protein (essen- tial amino acids and/or total nitrogen) and energy sub- strates (carbohydrates, fats, or proteins). However, these deficiencies are almost always accompanied by micronu- trient (minerals and vitamins) deficits. Manifestations of PEM differ depending on the duration, the severity, and the combination of these deficiencies. In the early stages,

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