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The preschool survivor and the nutritional crisis at school entrance

The nutritional status of the children who grow up in Tezonteopan stabilizes at about 20 months of age, and their rate of weight growth becomes similar to that observed in well-nourished populations. The increments in linear growth are of a smaller magnitude than those in weight, and as a result, the children from the village experience a progressive increment in weight relative to height. Ramos Galván ( 1969) refers to this phenomenon as homeorrhexis.

All the study children were still being breast-fed at 20 months, and their breast milk intake was about 400 ml/day (i.e., 35 ml/kg of body weight). The consumption of non-breast-milk foods, such as tortillas, corn atole, and beans, was low, and these foods were of poor quality. The total daily energy and protein consumption were 526 kcal and 11.2 g, respectively (A Chávez and Martínez, 1982).

How is it possible that the 20-month-old children from Tezonteopan can stabilize their nutritional status if they are surviving on such a low food intake? It almost seems impossible that the unsupplemented children could gain weight as fast as the supplemented or well-nourished children who consumed at least twice the amount of food. At this age the physiological needs of the child decrease and there is also a large adaptive reduction in physical activity, however, the child may still be unhealthy, The findings that by 20 months the unsupplemented child has a stable food consumption and energy expenditure, and that his activity level decreases in relation to the supplemented child, support this hypothesis.

The pattern of changes in body proportions is interesting. The malnourished children are born with shorter legs, and during the first eight months the size of the legs substantially catches up with that of the rest of the body. Between 8 and 20 months, the legs and the trunk of malnourished and well-nourished children grow at the same rate. However, after 20 months the growth rate of the legs of malnourished children again declines in relation to the well-nourished children.

The rate of increase in head circumference is analogous to the growth rate of the legs. This rate is the same in supplemented and unsupplemented children until 20 months of age, after which the rate declines among the unsupplemented children. Given this finding, why do the unsupplemented children who experience homeorrhexis seem to have large heads? The reason is that the small circumference of the thorax, coupled with a relatively large waist circumference, gives the child the appearance of being younger with a normal head size.

It is possible that the ratio between head and thorax circumference, rather than weight-for-age or weight-for-height, is the best indicator of nutritional status between 20 months and six years. This ratio is always < 1 for malnourished and > 1 for well-nourished children. Other indicators that might be sensitive to the nutritional status at this age are the ratios of upper to lower body length and of thorax to head circumference.

The severity and frequency of infections decrease beginning at 20 months. The duration per episode of diseases such as respiratory infections and diarrhea declines among the well-nourished relative to the malnourished.

At this age there is also some degree of stabilization in neurological function and mental performance. Beginning at 20 months of age, the unsupplemented children increase their performance at the same rate as the supplemented children, although the latter maintain a constant 10% to 15% advantage. By three years of age, the unsupplemented children almost reach the level of the supplemented children in language development and social behavior. However, after a short time their curves separate again, and later the unsupplemented show similar improvement rates as the supplemented children.

The differences in physical activity that can be attributed to the food supplementation are remarkable, and between 20 and 36 months there is a sevenfold difference in favor of the supplemented children.

Between 20 and 40 months, the household time-sampling methodology that was previously used to assess behavior was switched to a method based on placing the child in an open-field square area that had toys on one side and the mother on the other. This method allowed behavior to be studied at a predetermined time and place. The differences in behavior between supplemented and unsupplemented children remained constant. The unsupplemented children did not move around the square area, did not play with the toys, and did not move from their mothers' sides, where they remained crying and requesting to be held in their arms. By contrast, the supplemented children played with the toys, showed them to their mothers, and moved around the square area without fear or insecurity.

These results show that the malnourished children do not experience complete compensatory adaptations beginning at 20 months of age. These children are shorter, more ill, and heavily dependent on their mothers because they have a withdrawn personality. It is difficult to understand the basis for the insecurity experienced by malnourished children. It could be caused by a general feeling of weakness or lack of control of the environment, and/or by their immature personalities. These characteristics of insecurity and fear are responsible for the crisis faced by the malnourished child when he enters school for the first time.

At around six or seven years of age, the homeorrhetic mechanism observed among malnourished children (i.e., to spare weight at the expense of height) is reversed. At this age the children increase their linear growth rate at the expense of weight, and several symptoms of malnutrition begin to appear. Table 2 shows the difference in weight and height between the well-nourished and the malnourished children at the end of the preschool and at the beginning of the school period.

Beginning at five years, the unsupplemented children begin to catch up in linear growth, and by eight years they have reduced their deficit with respect to the supplemented children by about 4 cm. By contrast, the deficit in weight of the unsupplemented children increases during this period of time.

When applying the Jenss reference growth model to the children of Tezonteopan, it was found that the unsupplemented children experience their maximum deviation in growth rates at five to seven years of age (A Chávez and Martínez 1982).

The morbidity data indicated that at six and seven years of age the malnourished children experience a small and statistically nonsignificant increase in the number of episodes and duration per episode of illness when compared with the supplemented group. This finding might be explained by the exposure to new microbes in school.

Results from the Terman Merrill development test, which was periodically applied after the children were four years of age, show statistically significant between-group differences at both six and seven years of age (Figure 13). Whereas the supplemented children improved their IQ scores substantially, the unsupplemented children showed negligible improvements. This indicates that the village environment limited the mental performance of the unsupplemented children but not that of the supplemented children.

In the school, the children were observed every 45 seconds for 1.5 hours at arrival and before leaving the school for the day. Twelve behavioral items were recorded, and the children were unaware that they were being observed (Schlaefper, 1986). There were large between-group differences in school behavior and performance. Table 3 summarizes 3,240 behavioral observations per year per child. Statistics are not presented, due to the large sample size and the large between-group differences. The first column shows the results of the second daily observations and the second column shows the results that include both daily observations. These two columns are presented because the unsupplemented children performed even worse at the end of the day, perhaps because of fatigue. This is likely to have occurred because by the end of the day these children reduced their level of activity and increased the time spent sleeping. Unsupplemented children participated less in class, were more distracted, slept more, played less, and cried more on arrival at school than their supplemented counterparts.

TABLE 2 Differences in Average Weight and Height Between Supplemented and Unsupplemented Children

TABLE 3 Classroom Activities of Children Percentage of Time in Activity in 3,240 Observations During 3 Hours in the First School Year

^a Obey instructions, participate or interact with the teacher.
^b Look at the teacher, read or look at the book or answer in chorus.

There were also substantial between-group differences, which are difficult to interpret, at six and seven years of age in a series of written tests. The unsupplemented children had an average grade of 6.5+1.9 out of 10, and 38.3% failed to pass the school year. By contrast, none of the supplemented children had to repeat the school year, and their average grade was 8.1+0.5.

Several teachers, who were unaware of which group the children belonged to, were trained to apply several tests of knowledge to the study children. Table 4 shows the results of these tests. It indicates that there were between-group differences in favor of the supplemented children, even at the beginning of the school period (see Detroit-Engel test). This result is interesting, because none of the children received preschool education. By the end of the school year, the between-group differences in the knowledge tests were even larger, perhaps as a result of the school learning experience.

The knowledge of the children was also measured during the second year. However, the between-group comparisons are invalid, because the large proportion of unsupplemented children who repeated the school year had been previously exposed to these tests. In addition, two unsupplemented children were taken out of school by their parents.

TABLE 4 Results of Tests in the First School Year

The teenager who was malnourished as a child

Food supplementation was ended when the children were 10 years of age. The children continued to be followed afterwards to assess their physical, mental, and behavioral characteristics. These data provide answers to the question regarding the functional consequences of early childhood malnutrition.

Poorly fed adults living in socioeconomically disadvantaged areas have several functional limitations. It has been proposed that these limitations are the result of racial or social factors such as low maternal education and lack of stimulation. The hypothesis tested in this book, which has also been proposed by others, is that malnutrition is a determining factor of these functional limitations.

It was recently stated that malnutrition only affects physical growth and that malnourished individuals are "small but healthy" (Seckler, 1982). To clarify this issue, we analyzed the data when the children were 18 years old, an age at which it is assumed that human development has stabilized. However, the mental and behavioral data indicate that this assumption is incorrect and that this stability is perhaps only observed among supplemented women. It is important to understand why the remaining three groups were still developing. Is this an impact of malnutrition or the rural environment, or is it simply a methodological artifact?

It has been stated that the malnourished individual is like a runner who arrives late but is able to make it to the finish line. However, it is likely that in many of the tests there is a learning component that takes place later among malnourished individuals and this might explain the still evolving development. The fact that the rate of development has not stabilized by 18 years of age complicates the interpretation of the results, and definitive conclusions cannot be reached. This indicates that these young adults should be observed for at least two more years.

The growth in height of the supplemented women stopped during early adulthood. The age at menarche was significantly earlier for the supplemented than for the unsupplemented women (12.9+1.3 vs 14.4_1.6 years). The age at menarche of the unsupplemented women was earlier than the age reported in 1972 by women under the age of 36 years (15.3+1.4 years).

The difference between the supplemented and unsupplemented teenagers can be explained by their different nutritional histories. But why is there a difference in the age at menarche between unsupplemented women in the present study and women 15 years before? Perhaps the difference is related to changes in the village and the presence of the researchers. If this is the case, then it is reasonable to think that menarche might be one of the most sensitive indicators of small changes in nutritional status and in social and health conditions.

The maximal difference in height (14.1 cm) between supplemented and unsupplemented women takes place at menarche. However, supplemented women stopped growing at 15.5 years of age, when they had an average stature of 155.3 cm (A Chávez et al., 1991). The unsupplemented women accelerated their growth velocity before menarche and continued growing until they were 16.5 years old and had reached 145.7 cm, only 9.6 cm less than the supplemented women. This means that the delay in the onset of menarche allowed the unsupplemented women to grow for a longer time and to catch up partially in linear growth in relation to the supplemented women (Figure 14).

The growth in body weight continued until the women were 18 years old. The supplemented women began to slow down their weight growth velocity at 15 years of age. At this age they reached 54 to 55 kg but still gained 5 kg in the next three years. This increase does not seem to be explained only by fat accretion, since the skinfolds stopped increasing at 15 years of age (Figure 15). The maximal difference in weight (12.5 kg in favor of the supplemented group) occurred at 15 years of age. However, as also occurred with height, the unsupplemented women were able to gain weight for a longer period of time and therefore make up some of the difference. The skinfolds of unsupplemented women continued to increase gradually until they were 18 years of age (Figure 15).

The effects attributed to supplementation on growth are similar, although more pronounced, among men. The differences in height between supplemented and unsupplemented men reached 14 cm in favor of the former between 12 and 13 years of age. However, the unsupplemented children experienced catch-up growth between 15 to 17 years of age, and their height deficit diminished to 7 cm by 18 years of age.

The weight gain pattern is somewhat different in men and women, since both supplemented and unsupplemented men continued to gain weight up to the age of 18 years. Therefore, two additional years of follow-up would give us a better answer regarding the impact of malnutrition on young adult male weight gain.

The skinfold data for men indicate that both groups experienced a parallel increase, although the skinfolds of unsupplemented men were 30% thinner than those of their supplemented counterparts (Figure 15). This pattern is similar among women.

The most important finding regarding mental development is that the disadvantages of the unsupplemented children observed at the end of the follow-up are very similar to those observed early in life. Figure 16 shows that unsupplemented males have their lowest scores in the Terman Merrill tests of mental development at the end of the school period. At this age the unsupplemented males scored 70 points, which is below normal, and the supplemented males scored 85 points. The unsupplemented boys began to recover some of their deficit in mental development at 14 years of age and by 18 years they were still showing improvement. More years of follow-up will be required to learn the ultimate significance of this partial recovery. Among girls, the between group differences in mental development, which favor the supplemented group, narrow after 15.5 years of age. However, this is mainly due to a slowdown of the supplemented group rather than to an acceleration in the development of the unsupplemented group.

The physical condition of both groups was assessed during the school and the adolescent periods. The only difference during the school period was that the supplemented children could run faster, although they did not have more endurance. However, large differences in physical performance emerged after 15 years of age. There was more than a twofold difference in the number of deep knee bends that could be performed by the supplemented children before and after 15 years of age (30 vs 70 deep knee bends). By contrast, the increase among unsupplemented children was only from 30 to 50 deep knee bends (Figure 17). Similar trends were observed with sit-ups. (Figure 18). There were few between-group differences in the physical performance of women, but supplemented women had a better performance in the push-up exercises.

It is remarkable that the between-group differences in character and personality observed early in life remained during adolescence and early adulthood. Among supplemented women, six ventured out of the village to seek employment when they were an average of 18.2 years of age, and three were successfully employed. By contrast, none of the three unsupplemented women who attempted this when they were an average of 20.3 years old were employed outside the village. Two of the supplemented women ( 10.5%) and eight of the unsupplemented women (40%) married before 18 years of age.

Both groups had an average of about seven years of schooling. This lack of difference in formal education could be due to the limited educational opportunities in the village. However, two subjects of the supplemented group are still going to school and this will change the average. The formal schooling of men was similar in both groups (unsupplemented vs supplemented, 7.3 vs 7.9 years). Four of the unsupplemented men (20%), and none of the supplemented men, were married at 18 years of age or less. The three supplemented children who married did so when they were 20 or 21 years old.

Among men, there were between-group differences in the type of occupation and the age of migration. By 18 years, four of the unsupplemented group had sought, without success, a nonagricultural occupation. By contrast, seven of the supplemented group were working in nonagricultural activities (six are dishwashers in restaurants outside the village and one is still going to school).

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