We believe that if the environment is controlled and specific chemical exposures are changed (e.g., +APAP, +dietary SAA), we will observe metabolic changes that can be ascribed to the respective exposures. High resolution 1H-NMR, liquid chromatography, and mass spectrometry (MS) are well suited for investigating changes in body fluid composition because a large number of metabolites are present in body fluids, many metabolites can be detected simultaneously. Examples are available from the studies of Nicholson and coworkers (23, 24).The use of multivariate statistical analysis of NMR data to evaluate metabolic responses of living systems is under development for toxicologic screening of pharmacologic compounds (25). The principles for detection of chemical interactions in free-living humans are the same; in effect, changes in metabolic profile are expected to provide a sensitive means to non-invasively detect conditions of risk for toxicity and pathology.