Definition of a chemical specific adjustment factor for human interindividual differences in kinetics for glutamates (E620-625) following oral intake in the absence and presence of food

Previously a chemical-specific adjustment factor (CSAF) for human interindividual variation in kinetics (HK_AF) was defined for glutamates (E620-625) based on steady-state human plasma and brain glutamate levels. The present study defines this HK_AF based on kinetic data upon oral intake of monosodium glutamate (MSG) by human individuals in the absence or presence of food. Data on maximum plasma glutamate levels (C_max) following oral intake of MSG were obtained from literature. The median HK_AF values obtained amounted for the 95th, 97.5th and 99th percentile to 1.86, 1.98 and 2.13 for MSG exposure without food and to 1.86, 2.00 and 2.15 with food when assuming normal distributions for the Monte Carlo simulations and excluding studies with SE > 20 % of the mean. Assuming lognormal distributions the values amounted to 1.97, 2.29 and 2.65 without food and to 1.92, 2.21 and 2.54 with food. Corresponding average HK_AF values weighted for the number of study subjects were comparable. These values are in line with the HK_AF values previously obtained under steady-state conditions for plasma and brain-related data, and together point at an HK_AF for interindividual differences in kinetics of 2 to be used when deriving an acceptable daily intake (ADI) for glutamates.