Effects of chronic protein-calorie malnutrition on the kidney

Protein-calorie malnutrition is a widespread public health problem that contributes considerably to mortality and morbidity in areas where it is prevalent [1, 2]. A look at the world distribution of protein-calorie malnutrition indicates that the areas most affected are those countries where large proportions of the population are living under conditions of limited social and economic development [1]. The United States has considered itself one of the best-fed nations of the world. While this may be true, its attitude of self-satisfaction was challenged seriously by findings reported recently by the National Nutrition Survey [3]. Many persons, particularly among the lower income groups, were found to be malnourished. The growth of children under six years of age was below desirable standards in a number of areas. A high incidence of iron deficiency anemia was observed in infants and young children and in women during their reproductive years.Protein-calorie malnutrition is more than a medical problem. Social, cultural and economic factors are involved. In underdeveloped countries, it results from two main factors: a diet that is quantitatively and qualitatively inadequate plus superimposed stress, usually of infectious origin [4]. A deficient diet results, in turn, from varying combinations of low food production, inadequate preservation and distribution of foods, restricted purchasing power, poor food habits and deficient knowledge of the relation between diet and health. Excessive incidence of infectious disease is a consequence of poor environmental conditions, inadequate knowledge of epidemiologic factors, poor personal hygiene and insufficient health services. These factors are interrelated and act synergistically to the detriment of nutritional status. The clinical result depends on many determinants: on the severity and duration of the nutritional deficiencies of protein and calories, on the relative importance of the deficiency of protein to that of calories, on the nature and severity of other associated nutritional deficiencies, on the age of the person affected and on the presence of other complications. The mild and moderate forms occurring in children, frequently unrecognized and misinterpreted, are primarily characterized by inadequate growth and development. In adults, malnutrition reduces weight, performance and resistance to infection [4].Before describing the changes in renal structure and function which occur in malnourished humans or animals, it is crucial to appreciate that at this stage of our knowledge it is very difficult to determine which changes reflect a direct deleterious effect of malnutrition on the kidney and which represent an adaptation by the kidney to the nutritional insult. The former state implies a pathological change, the latter a physiologic response