|Causes and Mechanisms of Linear Growth Retardation (International Dietary Energy Consultative Group - IDECG, 1993, 216 pages)|
|Onset and evolution of stunting in infants and children. Examples from the Human Nutrition Collaborative Research Support Program. Kenya and Egypt studies|
The etiology of the early onset of stunting is diverse among populations of varying biological, environmental and cultural circumstances. This is exemplified within the Nutrition CRSP project, which took place in three different populations and ecological conditions. Within each study area a different mix and varying proportions of causative factors were identified. At least in Kenya, and probably in Mexico, the problem has its antecedents in prepregnancy and pregnancy. Powerful determinants of the infants' size at birth and during the first 6 months of life are maternal size upon entry into pregnancy, and weight and fat gain during pregnancy and lactation. In all three countries a low pregnancy weight gain was observed. Notably in Kenya, where the energy intake of the mother decreases progressively throughout pregnancy, not only do mothers gain only half as much as European or North American women, but they even lose weight and fat in the last month of pregnancy, and some mothers gain no weight or lose weight during the whole of pregnancy.
Mothers in Kenya start lactation with relatively poor fat stores. Although their energy intake increases somewhat during lactation, preliminary estimates suggest that these increases may be insufficient to maintain their bodily integrity, to carry out their normal tasks of daily living, and to produce a sufficient amount of milk for optimal infant growth.
In addition to an energy deficit, diet quality is a problem, particularly in Kenya and Mexico and less so in Egypt. Intakes of animal products and animal protein are very low. Zinc and iron intakes are not only low, but the bioavailability of these nutrients is poor because of the high phytate, fiber and tea content of the diet. Also vitamin B12 intake is extremely low, and at least mild-to-moderate iodine deficiency (IDD) is present in Kenya. The above micronutrients have been demonstrated to affect the linear growth of the Kenyan children, even after confounding factors have been controlled.
The early use of supplemental feeding in Kenya is a double-edged sword. On the one hand, there is a slight increase in febrile illness and possible displacement of breast milk intake in the supplemented infants, although mothers do not decrease breast feeding frequency and duration. On the other hand, even the modest amounts of available zinc and B12 in supplemental foods appear to have a positive effect on linear growth.
Morbidity, particularly in the Egyptian children, but also in the Kenyan infants and toddlers, has a negative impact on attained length in the 6 month old infant and also on the rate of linear growth. Diarrheal disease is very frequent in Egyptian infants and toddlers. Household sanitation level in Egypt is a potent determinant of growth, no doubt mediated through diarrheal disease.
In addition to parental size and household sanitation, cultural patterns of child rearing appear important, as demonstrated in the Egypt study. An important determinant of the toddler's linear growth from 18 to 30 months was whether or not it was still being breast fed. Those who were partially breast fed grew better than those who were fully weaned. Not only did the partially breast fed child benefit from the nutritional advantages of breast milk, but also from the higher quality supplemental feedings compared to the fully weaned child who partook of the regular household diet. Apparently, the breast fed child is perceived as requiting more nurturing.
In all three country studies the major deceleration of growth occurs in the first 6 months of life and probably continues throughout the first 12 to 18 months (although not observed). From 18 months onward the quantity and quality of the diet and environmental factors do not permit catch-up to the normal or near normal centiles observed in the newborns. Beyond infancy the rate of growth is normal but at a very low level, below the 5th centile in Kenya and Mexico. Little catch-up is seen in the schoolchildren and in late adolescence in Kenya, although the Egyptian children appear to improve in linear growth, as evidenced by improved height-forage Z scores compared with the toddlers.
Acknowledgements - Research was supported by: USAID Office of Nutrition Grant, No. DAN-1309-SS-1070-00 and Cooperative Agreement DAN 1309-A-00-9090-00 World Bank (Data Analysis)
Special acknowledgements are made to the Kenya project field and support staff at UCLA School of Public Health and University of California, Berkeley (UCB). Department of Nutrition and the University of Nairobi, Kenya: N.O. Bwibo, MD, PhD: Cp PI (University of Nairobi). A.A.J. Jansen, MD, PhD: Kenya Project: Training and supervision of anthropometry and pregnancy outcome. M. Baksh, PhD: Kenya project: Former field director. E. Carter, MD, PhD: Kenya project: Former field director. S. Oace, PhD: Analyses of vitamin B12 levels in breast milk (UCB). S. Murphy, RD, PhD: Nutrient data base (UCB). D. Calloway, PhD: Program Director Nutrition CRSP and nutrient data base development (UCB). G. Beaton, PhD: Consultant to Nutrition CRSP Management Entity (UCB). S.W. Andersson, MS: Directed food intake data collection in the field. L. Ferguson, PhD: Data analyses and statistical advice.
Special acknowledgements are made to the Egypt project field and support staff at UCLA School of Public Health, University of Kansas, and Purdue University, and the Nutrition Institute, Cairo, Egypt: O. Galal, MD, PhD: Co-PI (UCLA). N. Jerome, PhD: Co-PI (University of Kansas). N. Kirksey, PhD: Co-PI (Purdue University). M. Shaheen, MBBCH, MSc: Data entry (UCLA). F. Shaheen, MD, PhD: Formal field director (Institute of Nutrition). W. Moussa MD, PhD: Food intake (Nutrition Institute).