(introductory text...)

The results of correlational and supplementation research studies in humans and experimentation in animals, however, were insufficient to justify the main-effect model. Gradually, most investigators recognized that a bivariate approach of simple linear causality was not conducive to an understanding of the developmental effects of undernutrition among poor children (POLLITT and RICCIUTI, 1969; RICHARDSON, 1974, 1980; RICCIUTI, 1981; RUSH, 1984; GBANTHAM-MCGREGOR, 1984). It became apparent that undernutrition was a multifactorially determined human condition, far too complex to be reduced to the blueprint of the main-effect model. The model constricted the alternatives for the recognition and measurement of factors that coexisted and interacted (see footnote 3) with protein and energy malnutrition and contributed to the nature of the final developmental outcome. In other words, the model lacked the sensitivity to account for what was observed in the field as well as for some of the findings of studies on human populations. Some of these findings are reviewed below, underscoring the basic issues that evidenced the need to drop the main-effect model and pointed in the direction of a new paradigm. The review is primarily intended to uncover contradictions in the findings of different types of studies, which reveal the inadequacies of the bivariate model. Three main issues will be addressed:

1. discrepancy in the findings between the developmental outcome of primary and secondary malnutrition;

2. effects of favorable and unfavorable social environmental circumstances in the developmental outcome of undernourished children; and

3. the differences in the effects produced by nutritional supplementation with and without health care and education stimulation.