Zinc nutrition and growth retardation

Abstract

Human growth retardation from zinc deficiency was first reported over 40 years ago. More recently marginal zinc deficiency was shown to occur during pregnancy and infancy, and to be prevalent in children throughout the world. Zinc with or without macronutrients and other micronutrient deficits may also occur in patients with gastrointestinal disease. Particular attention must be given to the suboptimal intake of zinc which results in growth retardation. The single most important cause of nutritional growth retardation (NGR) worldwide is poverty related malnutrition involving multiple macro-and-micro nutrient deficits. NGR is an underappreciated entity in pediatric endocrine clinics since these patients do not manifest clinical evidence of malnutrition or overt nutrient deficits. A deceleration in body weight progression and decreased growth rates are the only clinical manifestations of the altered nutrient status. The growth deceleration occurs as an adaptive response to suboptimal nutrition to maintain equilibrium between genetic growth potential and nutritional intake. However the potential effects of suboptimal zinc intake in patients with NGR may be difficult to assess as there are no good clinical markers pertaining to this mineral. Zinc is known to be an essential micronutrient involved in growth, though the mechanism(s) by which zinc deficiency impairs growth has not been elucidated. Several hundred zinc-containing nucleoproteins are involved in gene expression of multiple proteins, many of them are important for growth. Zinc deficiency reduces IGF-I production, and may decrease cellular IGF-responsiveness. This may explain why the zinc status of GH deficient children significantly affects their response to GH treatment. In experimental models mild restriction of energy appeared to be more important in regard to growth retardation than suboptimal zinc intake, and the simultaneous restriction of energy and zinc did not augment the growth deterioration of chronic suboptimal nutrition. The USDA food guide is a simple guideline which should serve the needs of pediatric endocrinologists when evaluating the quality of the dietary intake of a short child and to provide guidelines for food intake to the patients.