|Early Supplementary Feeding and Cognition (Society for Research in Child Development, 1993, 123 pages)|
The provision of health and nutrition services is a means of promoting growth and development among children. In the United States, for example, although the specific objectives of food assistance programs are often not clearly defined, some programs (like the federally funded Special Supplemental Food Program for Women, Infants, and Children [WIC]) target nutritionally at-risk groups in order to prevent growth and developmental delays associated with malnutrition (Pollitt, Garza, & Leibel, 1984; Rush et al., 1988). Do the results of the Guatemala study provide a public health justification for food assistance programs such as WIC? In particular, do the data support a claim that such programs will help prevent cognitive developmental delays? Such preventive effects would have broader social and economic implications if it were to be shown that these kinds of delays affect work capacity and productivity.
The findings that we report support the assertion that, among nutritionally at-risk infants and children, early supplementary feeding contributes to a salutary development of the complex mental abilities required in an industrialized society among those at the lowest socioeconomic levels. However, they do not support a claim that the provision of food alone assures a significant net increase in daily intake. The Guatemala study was a major undertaking, with a solid and efficient administrative infrastructure created for research purposes. There was close access to the target group and continuous prompting to attend a station, where subjects received the supplement and socialized with other people. Without this prompting, the food supplement may not have had the desired effect. In their comprehensive review of supplementary feeding programs in developing countries, Beaton and Ghassemi (1982) concluded that the net increases in food intake were often lower than intended.
A related issue regarding treatment effects and their programmatic implications is the nutritional status of the target population. The prevalence of growth retardation in the population studied in Guatemala points to a high risk of malnutrition among infants and children. For example, a recent analysis of anthropometric data of subjects who had been measured at 3 years of age showed that 25.8% of the sample had severe stunting (3 standard deviations or more below the reference median) and that 42.5% had moderate stunting (2.9-2.0 standard deviations below the median) (Martorell, Rivera, Kaplowitz, & Pollitt, 1991). These estimates are similar to those made prior to the initiation of the longitudinal study in 1969 (Martorell, Habicht, & Klein, 1982).
The external validity of the Guatemala findings must be assessed in context, and generalizations are restricted to populations with a nutritional status similar to that in the rural villages in Guatemala. Moreover, the interactions between the nutritional treatment and SES indicate that, even within these populations, there is a differential response to treatment. Not all those in a nutritionally at-risk population benefited from the intervention.
On the surface, it may appear that findings of SES x treatment interactions speak clearly in favor of targeting treatment to individuals of lower SES. However, a closer look shows that the problem is more complex The interaction between treatment and maximum grade attained indicates, that individuals who may already have some social and educational advantages may be helped to excel even further by nutritional supplementation. Programmatically, it may be easiest to identify and target only those at the lowest end of the SES distribution within a community, but doing so means that other children who could benefit from the supplement will not receive it.
From a policy perspective, it must be recognized that the social or economic significance of the psychological test findings obtained in the Guatemala study is not readily apparent. While the construct validity of the tests was supported on theoretical grounds, no assessment was made of their predictive validity with reference to a behavioral criterion such as social adjustment or work productivity. The wide age range in the sample precluded such an assessment since many subjects were still in school and not earning any income. Moreover, to our knowledge, there is no relevant information from comparable rural populations in Latin America that could be used to establish the ecological significance of the Guatemala findings. Thus, the test score differences cannot be translated into other, more tangible terms, such as work productivity, earnings, or social adjustment. Although it is theoretically justified to assume that variation in scores on tests of reading and numerical ability are associated with variations in social and economic behaviors, it is also conceivable that such covariations may be lower than expected in a society in which basic human needs remain unmet.
The effects of public health programs, particularly behavioral effects, need to be analyzed in the context of a society's explicit and implicit social policy. In the context of rural Guatemala, the benefits of a supplementary program in enhancing development must be contrasted with the consequences of other existing conditions that counter such development. The school system, for example, is terribly inefficient and does not respond to the basic educational needs of the population (Gorman & Pollitt, 1992). Less than half the children enrolled in the first grade finish primary school, and many remain functionally illiterate. It is highly unlikely that the provision of food will prevent or remedy the consequences of not receiving an adequate formal education in a changing society.
Programmatic actions that focus on unmet nutritional needs and that have beneficial effects on human cognitive development are potentially a step forward in social policy. However, in our view, such actions are deceptive if they are framed in the context of a social policy that disregards other basic human needs and does not attend to the overall quality of life. Unmet nutritional needs generally coexist with, among other things, unmet needs in education, housing, sanitation, and health care. Only by meeting all these needs in conjunction with nutritional needs will we have truly moved forward toward a fair, humane society that sustains the rights of children and fosters cognitive and social-emotional development.