|Activity, Energy Expenditure and Energy Requirements of Infants and Children (International Dietary Energy Consultative Group - IDECG, 1989, 412 pages)|
|The relationship between undernutrition, activity levels and development in young children|
|4. Mild-to-moderate undernutrition|
A Mexican study of nutritional supplementation (CHAVEZ and MARTINEZ, 1982) is probably the most critical one for the present considerations. The study was prospective, began before the birth of the child, and longitudinal measures were taken of both activity and development throughout the first 2 years of life.
A cohort of village children were studied in the first year, and in the following year a second cohort were given nutritional supplementation and studied in a similar way. The mothers were supplemented in pregnancy and their children were supplemented throughout early childhood. Time-motion techniques were used, in which foot contacts with the supporting surface were counted to provide an activity rating. The supplemented children showed a higher level of activity from 8 months of age. Their activity increased steadily until they were six times more active than the non-supplemented group by 24 months. The supplemented children had higher DQs on the Gesell Schedules throughout the two years.
This study has frequently been cited as evidence for reduced activity being the mechanism linking undernutrition to poor development. In Figure 3, the activity data have been plotted on the same graph as the Gesell subscale scores of the children. It can be clearly seen that, far from the increased activity leading to improved development, there is little association between the two. The supplemented children's development was better from birth. There were some fluctuations, but the difference showed no sign of increasing. The timing suggests that, if there is a relationship, improved development leads to greater activity. In addition, there are problems with attributing the increased activity to the supplementation alone. The groups were observed a year apart, and there was no control for the increased attention received by the supplemented children.
In a nutritional supplementation study in Bogota (SUPER et al., 1981), mothers were supplemented in pregnancy and their children from birth for three years. Observations were carried out when the children were 4 and 8 months of age. In a complex analysis, the results were presented in summary scales. At 4 months, the supplemented children had higher scores on the 'activity scales than the non-supplemented groups. This included 'gross body movements' and 'quiet play' as well as other variables. Children who received both supplementation and stimulation were especially active. There was no effect of supplementation at 8 months of age.
A large supplementation study was conducted in four villages in Guatemala. Pregnant women and children under 7 years were nutritionally supplemented on a self-selection basis. The children's behavior in several games was observed when they were 6 to 8 years old (BARRETT and RADKE-YARROW, 1985). The children who had received the most supplement in the first 4 years of life and when their mothers were pregnant, were compared with those who had received less. The high-supplement group was judged to be more active and exploring than the low-supplement group. However, it is not clear whether some of the supplemented children were still being supplemented. Also, self-selection could be a severe confounder in this study.