The absorption by human volunteers of glutamic acid from monosodium glutamate and from a partial enzymic hydrolysate of casein

Peripheral plasma concentrations of glutamic and aspartic acids and alanine were measured after ingestion of monosodium glutamate or a pancreatic hydrolysate of casein by human volunteers. The doses of each material were such that they contained similar amounts of glutamic acid. Plasma glutamic acid concentrations rose promptly after the monosodium glutamate but mean peak concentrations were well below those likely to cause neurological damage. Plasma aspartic acid concentrations also rose after the monosodium glutamate but the behaviour of plasma alanine concentrations suggested that intestinal transamination of glutamic acid was insufficient to cause an appreciable rise in alanine concentration in the peripheral plasma. Significant increments in plasma glutamic acid concentrations did not occur after the pancreatic hydrolysate of casein and it is probable that competition for absorptive mechanisms by other amino acids, both free and peptide-bound, causes absorption of glutamic acid to be slower from mixtures of peptides and amino acids than from monosodium glutamate itself.