Year: 2000
Type: article
Abstract: The field of pediatric nutrition has changed dramatically over the past 15 years with the growing appreciation that micronutrient deficiencies play an important role in explaining high rates of childhood mortality and morbidity in developing countries. Previous work had convincingly linked undernutrition (as generally measured by weight or height deficits) with higher rates of death in children under five (J Nutr 1994;10:2106S–22S). It is now clear that vitamin and trace element status are also important factors in childhood health. Although the importance of vitamins in maintaining general health and growth was realized with their discovery in the early twentieth century, only recently has it been appreciated that micronutrients have sizable impacts in reducing morbidity and mortality from infectious illnesses. For instance, suboptimal vitamin A status is associated with an increased incidence of respiratory tract and gastrointestinal tract infections, even when taking into account anthropometric measures such as weight for height. A series of intervention trials subsequently proved that in communities at risk of vitamin A deficiency, substantial reductions in infant and young child mortality can be made with periodic high dose vitamin A supplementation (JAMA 1993; 269:898-903). In addition to fewer deaths, reductions in rates of diarrheal disease, respiratory infections, and symptoms of dysentery have all been reported with periodic vitamin A therapy. More recent work has centered on the identification of those patients who would benefit most from vitamin A supplementation; for example, some studies have shown an increased incidence of respiratory infections when vitamin A is given to well nourished children (Pediatrics 1999;104(1):e1). In addition, biochemical recognition of vitamin A deficiency requires assessment of the acute phase response, since depression of serum concentrations of retinol can be due to the confounding effects of infectious illness or other inflammatory responses (Am J Clin Nutr 2000;72:146-53). Feasible methods of dietary supplementation such as fortification of cereals have also been evaluated (Am J Clin Nutr 2000;72:738–44), since periodic large dosing of the nutrient can be logistically difficult in low-income countries. If Vitamin A was the micronutrient of the 1980s and 1990s, zinc seems to be poised as the trace element of the new millennium. Recent trials of zinc supplementation have shown substantial benefits to children at risk of deficiency. Zinc supplementation has been shown to reduce the duration and severity of acute diarrhea in India (N Eng J Med 1995;333:839–44), as well as to improve outcomes in subsets of patients with persistent diarrhea in Perú (J Pediatr 1999;135:208–17). The incidence of acute lower respiratory tract infections has also been reduced with zinc supplementation (Pediatrics 1998;102:1–5). A recent analysis of randomized trials of zinc interventions was performed of studies in which infants and young children received 5 to 10 mg zinc for 5 or 7 days per week for 12 to 54 weeks. The pooled odds ratio for diarrhea incidence was 0.82 (95% CIs 0.72–0.93), and the OR for pneumonia incidence was 0.59 (95% CIs 0.41–0.83) (J Pediatr 1999;135:689–97). These data, when extrapolated to the millions of children at risk for diarrhea and respiratory morbidity and mortality worldwide, translate into a tremendous potential for reduction in childhood death and disease. Zinc supplementation, however, may not be for everyone. In children with severe protein energy malnutrition, a three-armed trial comparing placebo to two doses of zinc supplementation found a higher mortality rate among those receiving a very high zinc dose (Am J Clin Nutr 1998;68:742–8). Two general mechanisms through which deficiencies of micronutrients may contribute to infant and childhood illnesses are generally postulated: effects on the immune system, and an impact on weight gain and body composition. Vitamin A deficiency is associated with impaired natural killer cell activity, reduced mitogen-stimulation response by lymphocytes, and reduced humoral response to vaccines (Proc Nutr Soc 1999;58:719–27). Zinc deficiency has also been associated with perturbations in immune function, including reduced B- and T-cell functions, decreased delayed hypersensitivity reactions, impaired phagocytosis, and reduced cytokine production (Am J Clin Nutr 1998;68:447S–63S). Future micronutrient research should include studies of multiple micronutrient supplements, as researchers strive to define the ideal mix of nutrients for optimal health. Multiple micronutrient supplementation, for instance, have been associated with improved birth outcomes among HIV-infected pregnant women in Tanzania (Lancet 1998;351:1477–82). These studies call into question our entire conception of what is considered a nutrient requirement, and challenge the pediatric nutrition community to consider more broadly the role of micronutrients in health and disease.
Authors: Christopher Duggan, Robert D. Baker, Philip Rosenthal, Philip M. Sherman, Hans Büller
Institution: Harvard University
Language: English
Subfield: Nutrition and Dietetics
Field: Nursing
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2052468237