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J. LARRY BROWIY2 AND LAURA P. SHERMAIY
1Prepared for the International Dietary Energy Consultative Group (IDECG) Task Force workshop on malnutrition and behavior at the University of California, Davis, CA, December 6-10, 1993. This workshop was supported by IDECG, the Nestlé Foundation, Kraft Foods, and the International Union for Nutritional Science. Guest editor for this supplement publication was Ernesto Pollitt, Department of Pediatrics, University of California, Davis, CA 95616.
2To whom correspondence should be addressed: Center on Hunger, Poverty and Nutrition Policy, Tufts University, 11 Curtis Avenue, Medford, MA 02155.
Center on Hunger Poverty and Nutrition Policy, Tufts University, School of Nutrition, Medford, MA 02155
ABSTRACT Recent research findings have augmented the nutrition variable to a higher category of importance than previously appreciated. Inadequate nutrition can impair cognitive development and is associated with educational failure among impoverished children. This suggests that poor nutrition interferes with the formation of human capital, the cornerstone of a nation's social and economic development. Even temporary food shortages can produce adverse outcomes in developed as well as developing countries. The long-held concept of a critical period of brain development has been modified in light of the new understanding that developmental and morphological plasticity are far greater than previously recognized. This knowledge does not mean that there are no lasting adverse outcomes, but that from a policy perspective, intervention and rehabilitation can play crucial roles. This article highlights the relevance of this evidence to social and health programs and policies. J. Nutr. 125: 2281S-2284S, 1995.
INDEXING KEY WORDS:
The body of evidence discussed in this publication propels the importance of nutrition to the forefront of the national and international policy arenas. Recent research findings assign the nutrition variable a far more critical role than previously appreciated, one that has profound social and economic implications.
Poor nutrition interferes with the formation of human capital, the cornerstone of a nation's social and economic development. Even temporary food shortages can produce adverse outcomes, not only in developing countries but in developed nations as well McDonald et al. l 994). This outcome is independent of previous nutritional wellbeing or socioeconomic status. It is also true for both adults and children, although the nutritional status of poor children needs to be taken particularly seriously.
This article highlights the relevance of the newly emerged evidence to social and health programs and policies. For some years it has been recognized that undernutrition has significant adverse effects on cognitive development and school performance (Wachs 1995). What is now better understood is the degree of jeopardy poor nutrition poses to its victims and, ultimately, to national development. Moreover, forms of malnutrition considered moderate or even mild can impair both cognitive and behavioral development (Gorman 1995).
In terms of nutrition and child development, there is the proverbial good news and bad news. The long-held concept of a critical period in brain development has yielded to an understanding that developmental and morphological plasticity is far greater than previously recognized. This knowledge does not mean that there are no lasting adverse outcomes, but that, from a policy perspective, intervention and rehabilitation can play crucial roles. The bad news is that the extension of risk status beyond the window of a critical period means that youngsters are now understood to be in jeopardy of developmental impairment over a longer period of time Gorman 1995, McGregor 1995). The period of nutritional surveillance and evaluation should be extended to include not only preschool children but youngsters into adolescence as well.
Another reason for optimism in the heightened status of nutrition as a developmental factor is the recognition that supplementation can buffer some of the detrimental outcomes associated with poverty and related environmental factors (Pollitt et al. 1993). Good nutrition contributes to the development of complex mental abilities and is associated with better developmental outcomes. For this reason it is very important to ensure adequate dietary intake even when there is less ability to improve other social and environmental conditions of children. On the other hand, nutritional intervention alone is not a powerful enough factor over the long term. Supplemented children who are continuously exposed to adverse social and economic conditions are not adequately buffered from cognitive and emotional impairment (Galler 1986).
Although the findings on buffering, plasticity and the potential for rehabilitation are ripe with program significance, improved understanding of the interaction between nutrition and cognitive and behavioral development has important implications for both policy and program formation for two reasons. The first factor with significant policy implications is that adequate environmental and social supports necessary for healthy child development often are not in place for the children most likely to be undernourished - those who live in poverty. Moreover, poverty status and family income are directly correlated with cognitive development and child behavior (Sewell 1993), and the significance of income is so strong that it remains even when accounting for family structure. Undernutrition seldom occurs in isolation. It typically covaries with other unmet needs associated with poverty such as poor housing, poor schools, poor sanitation and minimal health care. These factors are interactive, with the variable of limited income mediating their relationship. For example, the incidence of growth failure among hospitalized poor U.S. infants and children was found to correlate with the season of the year. More children appear at hospital emergency rooms in the months after winter when expensive home-heating bills require diversion of family income from food to maintain shelter (Frank et al. 1991).
It is also important to consider that when food availability and quality are not adequate, the incidence of morbidity is usually higher (Pollitt 1989). Morbidity in turn causes depletion of nutrients due to malabsorption, diarrhea and inflammation. Diminished maternal caregiving also associates with mild undernutrition (McDonald et al. 1994), disrupting child-caregiver relationships. All these factors suggest that nutritional supplementation must be accompanied by broader, more multifaceted interventions.
The second factor is that the simplicity of the perceived linear relationship between nutritional intake and cognitive outcome, as previously described in the research, has been removed. A new understanding that cognitive impairment is produced by more indirect means suggests that rehabilitative interventions must address aspects of emotionality and employ a comprehensive approach that includes psychosocial supports. Although supplemental feeding programs for poorer infants and children may lead to improved complex mental abilities, food alone does not yield a significant net increase in performance (Pollitt et al. 1993). Because undernutrition affects not only mental function but emotional stability and behavior itself, nutritional supplementation may not be effective if appropriate environmental supports parental, schooling) are not in place as well.
A related policy issue emerging from the research data is the question of whether, in an era of scarce resources, nutritional intervention should be targeted to particular groups of children on the basis of income or age. Low-income children are disproportionately impacted by inadequate nutrition, not only in developing economies but also in industrial nations including the United States Pollitt 19941. In addition, research results indicate that the strongest effects of supplementation are in the earliest years of life.
On its face the relationship between socioeconomic status and exposure to inadequate nutrition makes the targeting of poorer children for intervention seem both humane and compelling. Research, for example, shows that the most undernourished children receive the greatest benefits from supplementation. But the problem is more complex because the interaction between intervention and important outcomes such as maximum grade attained in school indicates that undernourished children who previously had educational and social advantages excel further when aided by nutritional supplementation (Pollitt et al. 1993). Targeting children only at the lowest end of the socioeconomic status distribution would mean that supplementation would not go to many children who could benefit substantially.
A similar dilemma exists when considering which age group should be targeted for nutritional intervention. Although preschoolers are at he greatest developmental risk from undernutrition, school-age children are also at risk. For children who are in school, nutritional supplementation needs to be augmented with other interventions to enable them to remain in school as long as possible (Pollitt et al. 1993).
Finally, on the basis of what we know about the mechanisms by which nutrition affects children's development, current screening and assessment methods may not be adequate to measure the true effects of nutrition on young children. Specifically, the strong focus on IQ and school performance as measured by standardized testing appears to be inappropriate to assess the impact of nutrition on children's educational abilities. Functions associated with prefrontal cortex (attention, flexibility and impulsivity) are poorly tapped by the standard end point of IQ tests). Subtle but perhaps far more significant outcomes to measure may pertain to philosophy and structure of learning on the part of the child, reflecting the more complex interaction now known to exist between nutritional input and behavioral, emotional and cognitive development (Levitsky and Strupp 1994).
Also of policy relevance are the data suggesting that micronutrient undernutrition plays a considerable role in terms of limiting development. At one time it was thought that in developing countries inadequate protein was the most limiting factor in the diets of the poor. During the 1970s the epidemiology of undernutrition shifted from protein to overall dietary energy because it was learned that when the body lacks sufficient calories, it diverts protein from amino acid creation to supply energy. More recent research brings greater understanding of still other dietary deficiencies, most notably vitamin A, iodine, and iron (ACC/SCN 1993, Lozoff 1990). So critical are certain micronutrients that in the scientific community the term undernutrition has come to refer to the consumption of a diet that; is not only inadequate in quantity, but of a quality insufficient to meet physiological and developmental needs. Indicative of the importance of essential nutrients, for example, are research outcomes in which infants with iron deficiency anemia perform worse in mental and motor tests than do ironsufficient infants of a similar age. Low hemoglobin concentrations serve to compromise oxygen transport in the body, leaving children tired, lethargic and unable to concentrate. This condition appears to have a similar outcome to that of other forms of undernutrition in which inadequate dietary energy compromises a child's engagement with her social environment, thereby impeding cognitive and social development (Pollitt and Idjardinata 1993).
In the policy arena, the heightened importance of micronutrient malnutrition has concrete applications. Iron deficiency anemia is the most common nutritional problem in the world. Although rates are higher in developing nations, iron deficiency anemia is sufficiently the United States to constitute a serious public health threat - nearly a quarter of low-income youngsters experience this disorder. Most significantly, iron deficiency anemia lends itself to relatively simple and effective remediation through iron screening and supplementation programs. After iron supplementation intervention, developmental retardation is typically reversed (Pollitt and Idjardinata 1993).
Another factor touching on both housing and health policy is that iron deficiency anemia places children at higher risk of lead poisoning, which produces severe neurological disorders. Poor children face a double jeopardy - they are more likely to have diets deficient in iron and are more likely to live in leaded environments.
Other policy implications flow not only from new understanding in the arena of micronutrient malnutrition but from the broader findings that link overall nutritional status with cognition and behavioral development. Insufficient household food produces a trade-off much like the heat-or-eat phenomenon faced by households with insufficient food in cold climates (Frank et al. 1991), wherein verbal and social interaction between caregiver and child is diminished by the need to maintain adequate nutrition (McDonald et al. 1994). This trade-off seems to have a profound effect on school-age children who exhibit a diminution of classroom attentiveness, as well as a reduction in play and other social interactions (McDonald et al. 1994). Even temporary food shortages disrupt the behaviors of both children and parents (McDonald et al. 1994).
In terms of educational policy, particularly school preparedness, research findings suggest that undernutrition exacts a heavy toll in terms of illness and its effects on educability. This is especially true in developing nations where nutritional deficiencies and poor health in young schoolchildren are among the causes of poor school enrollment, absenteeism, early dropout and poor classroom performance (Pollitt 1989). Infection and malnutrition have a synergistic interaction among high-risk populations, making it difficult to separate their respective effects (Pollitt et al. 1993). It is known that the number of days absent from school because of illness correlate with cognitive test scores, and frequency of illness in the early years is a predictor of test performance in adolescence (Pollitt et al. 1993).
Evidence shows that in industrialized countries, school learning is impacted even by mild malnutrition. In terms of school preparedness, this suggests that policy initiatives to ensure that children have the nutritional basis for learning are critical. For the United States, research outcomes support efficacious use of school nutrition initiatives such as the lunch, school breakfast and summer food programs. For example, a study of the school breakfast program showed that poor children who participated performed better on standardized achievement tests and were late and absent from school less often than their peers who did not participate (Meyers et al. 1989). From a policy perspective, the ready availability of such programs indicates that the small investment they represent in terms of fiscal outlays are offset by substantial gains in terms of protecting the value of a nation's educational investments.
The policy relevance of the body of research described in the foregoing papers is relevant in both developing and industrialized national contexts. Clearly, however, the policy application will differ according to national approaches to protect the nutritional status of children and families. The relevance of new research findings to a national context, however, can be applied in terms of existing knowledge as summarized below:
1. Chronic mild undernutrition directly influences child development (cognition and behavior) by impeding social and environmental interactions, including the important child-caregiver relationship.
2. Cognitive and behavioral impairments associated with even mild undernutrition may last a lifetime.
3. Developmental plasticity indicates that children and adults may be affected by undernutrition at times other than the earliest years of life, but that with appropriate interventions some of the damage may be offset.
4. Undernutrition seldom occurs in isolation but is usually accompanied by other risk factors, such as family income and poverty status, which have implications for intervention strategies.
5. Intervention strategies are most effective when they are multidimensional, for example, involving not only nutritional supplementation but developmental, caregiver and educational components.
6. Nutritional supplementation cannot ensure that impairment will be corrected, but when accompanied by psychosocial intervention it can be highly beneficial.
7. Interventions targeting malnourished children and their families are likely to affect not only the individual but societal development as well, thanks to improvements in educational quality, workforce skills and productivity, economic competitiveness and quality of life.
By interfering with individual
potential and, consequently, human capital, undernutrition has been transformed from a
purely ethical matter to a major economic issue. Policy makers now have compelling
evidence that even mild undernutrition causes serious and often irreparable damage,
beginning early in life and continuing through adulthood. Although some adverse effects
may be reversed under the right conditions, undernutrition generally robs the individual
of the opportunity to achieve his or her potential and therefore deprives the nation of
its citizens' full contributions and productivity. These are exceptionally strong reasons
for intervention policy to ensure dietary adequacy through preventive measures, as well as
remediation where feasible.
ACC/SCN (19931 SCN News, No. 9.
Frank, D. A., Napoleone, M., Roos, N., Peterson, K. & Cupples, L. A. (1991) Seasonal changes in weight for age in pediatric emergency room: a heat or eat effect? Presented at the National Conference of the American Public Health Association labs.).
Galler, J. R., Ramsey, F. & Forde, V. (1986) A follow-up study of the influence of early malnutrition on subsequent development .4. Intellectual performance during adolescence. Nutr. Behav. 3: 211-222.
Gorman, K. S. (1995) Malnutrition and cognitive development: Evidence from experimental/quasi-experimental studies among the mild-to-moderately malnourished. J. Nutr. 125: 2239S2244S.
Levitsky, D. A. & Strupp, B. J. (1995) The enduring effects of early malnutrition: a history and perspective (in press).
Lozoff, B. (1990) Has iron deficiency been shown to cause altered behavior in infants? In: Brain, Behavior, and Iron in the Infant Diet (Dobbing, J., ed.), pp. 107-131. Springer-Verlag, London, UK.
McDonald, M. A., Sigman, M., Espinosa, M. P., & Neumann, C. G. 11994) Impact of a temporary food shortage on children and their mothers. Child Dev. 65: 404-415.
McGregor, S. G. (1995) A review of the studies of the effects of severe malnutrition on mental development. J. Nutr. 125: 2233S-2238S.
Meyers, A. F., Sampson, A. E., Weitzman, M., Rogers B. L., & Kayne, H. (1989) School breakfast program and school performance. Am. J. Dis. Child. 143: 1234.
Pollitt, E. (1989) Malnutrition and Infection in the Classroom. Unesco, New York, NY.
Pollitt, E. 11994) Poverty and child development relevance of research in developing countries to the United States. Child Dev. 65: 83-295.
Pollitt, E., Gorman K. S., Engle, P. L., Martorell, R. & Rivera, J. (commentaries: Wachs, T. D. &'Scrimshaw, N. S.) (1993) Early Supplemental Feeding and Cognition - Monographs of the Society for Research in Child Development, 58 (No. 7, Serial 235).
Pollitt, E. & Idjardinata, P. (1993) Reversal of developmental delays among iron deficient anemic infants treated with iron. Lancet 341:.1 -4.
Sewell, T. E., Price, V. D., & Karp, R. J. (1993) The ecology of poverty, undernutrition and learning failure. In: Malnourished Children in the United States (Karp, R.J., ed.), pp. 24-30. Springer Publishing, New York, NY.
Wachs, T. D. (1995) Relation of mild-to-moderate malnutrition to human development: Correlational studies. J. Nutr. 125: 2245S-2254S.
This I/D/E/C/G workshop was supported by the Nestle Foundation, Kraft Foods and the International Union of Nutritional Sciences (IUNS). This publication is available free of charge from
The Secretariat of IDECG c/o Nestle
Foundation P. O. Box 581 1001 Lausanne Switzerland thanks to a grant provided by the
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