|Chronic Energy Deficiency : Consequences and Related Issues (International Dietary Energy Consultative Group - IDECG, 1987, 201 pages)|
|Pregnancy, lactation and childhood: Report of working group 1*|
Since children have not been discussed at this workshop they are considered here only very briefly.
1. Recent studies of energy intake in exclusively breast-fed children indicate that their energy requirements, as judged by growth, can be met by much lower intakes than those proposed in the 1985 report, which were based on the observed intakes of formula-fed infants.
2. Information about the BMR of infants and young children is consistent and satisfactory, but very little is known about their levels of physical activity. To fill this gap, more work is needed on instruments for investigating activity in young children. This subject is one of high priority.
3. A great deal remains to be learned about the relation between energy supply and amount and pattern of growth. Decreased growth in length compared with international references (stunting) is extremely common in developing countries. Factorial estimates of the nutrient requirements of children are all based on increments in weight. It is a tenable hypothesis, based on some supportive evidence, that growth in length is determined by the supply of protein or of factors associated with protein in foods, and that growth in weight is determined by growth in length, in order to maintain body composition.
4. Therefore, more studies are needed of the relationships between the intakes of energy and nutrients and the amount and pattern of growth. Such studies are particularly illuminating if they compare groups with different dietary patterns and are particularly important for children below three years. A number of valuable studies of this kind were done in the 1970s, but they seem to have fallen from favor. A major difficulty was that many children are still partially breast-fed at 2-3 years of age, so that accurate estimates of intakes were virtually impossible. This problem could now be overcome by using heavy water.
There is some recent evidence that, when the energy intake of children is inadequate, before growth falls off, there is a decrease in physical activity. This is to be regarded as highly undesirable, because it limits the child's exploration of the environment and the development of social relationships.
There are numerous anecdotal accounts of apathy, with-drawnness, failure to make friends, etc. - effects that may produce a progressive handicap throughout life.
These considerations reinforce the need for studies on the physical activity of children in relation to energy intake and the development of appropriate methodology.
Analysis of the effects of chronic energy deficiency on the child's development is complicated by the fact that it is associated with many other handicaps of poverty.
Small body size from infancy and childhood and low weight-for-height maintain low but statistically significant correlations (.20-.30) with both comparatively low intelligence test scores and poor school achievement. These correlations are consistent across low-income populations in developing countries and are reasonably explained by the effects of nutritional history. However, these correlations do not explain the nature of the relationships between undernutrition and brain function; they are only a reflection of a possible bi-directional effect of a history of undernutrition.
Small body size and low weight-for-height have also been associated with low activity levels among infants and young children.
There is no single definitive work that has tested adequately the developmental impact of supplementation in early life. The data that exist point out that, among nutritionally-at-risk populations, supplementation has a mild but important beneficial effect on mental and social-emotional development during infancy and the preschool years. Likewise, supplementation increases activity level among nutritionally at risk infants and children.
In comparison to the effects of nutritional supplementation the effects of multifocal interventions (i.e., supplementation, health, education) are substantively greater. These beneficial effects are apparent even if the intervention begins after the first three years of life or passed the so-called critical period of brain growth.
Research needs in this area may be summarized as follows:
1. Determine the social environmental and health factors that increase the probabilities of developmental deviations among nutritionally-at-risk infants and children.
2. Determine the nature of activities that are particularly vulnerable under conditions of chronic energy deficiency.
3. Determine the cost to cognitive and social-emotional development of maintenance of energy balance by reduced activity among infants and children.
4. Establish the educational effects of undernutrition during the school period.
If the consequences discussed above are to be prevented, it is necessary to know why energy intakes fall below what is necessary or desirable. There are various possible causes:
1. Absolute lack of available food, e.g., during the hungry season. It is known that in such cases catch-up growth can occur when food supplies improve (Nepal). The question arises as to whether "stop-and-go" growth carries any handicap compared with more regular growth.
2. Even though food is available, the child may not be able to eat enough of it, because of low energy density, too widely spaced meals, etc.
3. Factors that influence the mother's activity may reduce the time available for cooking and child care.
4. Infections have a profound impact on appetite and energy intake.
The relative importance of different causes of low energy intakes of children will differ in different environments. A high priority should be given to in-depth case studies of families in different communities. The number of families studied need not be large. Where this approach has been used, it has proved extremely cost-effective.