Nutrition and Central Nervous System Development

Abstract

During the past two decades evidence from a variety of sources has accumulated, which demonstrates that severe early malnutrition can affect both brain structure and brain function. By contrast, animals malnourished after weaning showed smaller brains at the end of the period of malnutrition, but on re-feeding brain weight returned to normal. Subsequent studies have clarified the reason for the different responses. Brain growth is characterized by a series of cellular changes which take place in a sequential pattern. Early growth occurs primarily by repeated cell division as characterized by a linear increase in total organ DNA. Cell size as determined by weight/DNA ratio or protein/DNA ratio remains relatively constant. In animals, malnutrition occurring during the period of rapid cell division (hyperplasia) results in retardation in the overall rate of cell division, and hence ultimately results in fewer cells. This change is permanent. By contrast, malnutrition occurring during the period of hypertrophic growth results in curtailment of cell enlargement, a process which is reversible as soon as rehabilitation is instituted. Data from analysis of brains of children who died of malnutrition during the first year of life demonstrate a reduced number of cells. Thus, in the human, severe early undernutrition curtails cell division and results in fewer cells.