ABSTRACT
The interaction between nutritional status and the ultimate expression of neurotoxicity is complex and can be modified by a number of factors. Certain nutritional elements, such as pyridoxine, can be neurotoxic in excess, whereas a deficiency of another nutritional element, such as thiamine, can also influence neuronal functioning. Alternatively, a marginal nutritional status may become inadequate when a toxicant, such as alcohol, is ingested. The ultimate expression of the interaction between nutritional status and toxicants is reflected in the overall functioning of the nervous system. Furthermore, some foods that are routinely ingested in certain cultures contain neurotoxi cants. The developmental stage at which toxic levels of a nutritional factor are present can influence the expression of neurotoxicity. As described in detail below, high levels of phenylalanine can be toxic in certain infants because of an enzyme deficiency and can result in severe mental retardation. However, if dietary phenylalanine is restricted until the child is approximately five years old, the diet can be less restrictive after that age without affecting mental development. The precise nature of nutritional interactions and neu rotoxicants is difficult to delineate since one factor rarely changes alone.
