Abstract
The safety of food additives in the human food supply is determined by a variety of methods. Toxicity evaluation in animals requires the same concerns applied to drugs. Aspar-tame and xylitol are used to demonstrate the importance of host threshold in the induction of pathology. Host threshold is largely determined by genetics, species, sex and age. Metabolic processing of food additives, consonant with survival, depends on chemical structure, concentration, route of administration and duration of exposure. When the host threshold is exceeded, a metabolic overload exists straining all homeostatic mechanisms leading eventually to a pathological state. The significance of these pathological conditions in the absence of understanding the underlying mechanisms is open to question in terms of human risk.