Plasma Glutamate Concentrations in 1-Year-Old Infants and Adults Ingesting Monosodium L-Glutamate in Consommé

Abstract

ABSTRACT. This study tested the hypothesis that infants metabolize glutamate more slowly than adults. Eight l-yrold infants ingested 160 ml of a beef consommi: providing monosodium L-glutamate at 0, 25, and 50 mg/kg body weight. Plasma glutamate and aspartate concentrations were measured sequentially for the next 2 h. The results were compared to values noted in nine adult subjects ingesting equivalent doses of monosodium L-glutamate in consomme. In adults, mean (+ SD) peak plasma glutamate concentrations were 5.59 f 1.56, 10.2 + 2.08, and 17.0 f The ability of human infants to metabolize MSG has been one area of concern in considering glutamate's safety as a food additive. Olney (1-3) postulated that human infants metabolized dicarboxylic amino acids more slowly than adults, and projected theoretical plasma glutamate concentrations for infants at much higher values than those for adults following glutamate ingestion.The present study directly tested this hypothesis by measuring the plasma glutamate and aspartate response in 1-yr-old infants fed a beef consommi containing graded doses of MSG. The results of these studies were compared with previously reported (4) plasma glutamate and aspartate values in normal adults administered equivalent doses of MSG in the same consomm6. MATERIALS AND METHODSEight infants (four male, four female) were studied. The proposed study was explained to at least one of the parents and informed, written consent was obtained. The protocol of the study was reviewed and approved by the Committee on Research Involving Human Subjects of the University of Iowa.Each child ingested 160 ml of beef consommC providing 0,25, and 50 mg/kg body weight of added MSG in a balanced crossover design. Each infant was randomly assigned to receive consommi providing either 0 or 25 mg MSG/kg body weight, followed by the other dose at least 1 wk later. After these two tests had been completed and the results evaluated, each infant ingested consommi providing MSG at 50 mg/kg body weight. All tests were begun at 0800 h following an overnight fast.The monohydrate of monosodium L-glutamate was purchased from a local grocery store (Accent International, Pet Incorporated, St. Louis MO). The soup was prepared from a special beef consommk base supplied by the Ajinomoto Company (Tokyo, Japan). The composition of the soup base is shown in Table 1. As noted in Table 1, 160 ml of reconstituted soup contained 37 mg of free glutamate, for a mean dose of 4.1 mg/kg body weight. Thus, the true final doses of MSG studied in these infants were 4.1, 29.1 and 54.1 mg/kg body weight.Each infant was assigned by random allocation into one of two equal groups that differed with respect to time of blood sampling. Since only four blood samples were obtained from each infant after dosing, two different sampling schedules were utilized so as to obtain samples during the entire absorptive period. Blood samples at each dose level were obtained from four infants at 0, 30, 60, and 120 min After ingestion of the consommG Blood samples from ...

Monosodium Glutamate in the Diet Does Not Raise Brain Glutamate Concentrations or Disrupt Brain Functions

“…When MSG was added to this meal, the total rise in plasma GLU was about 2.8-fold (over baseline values) at 34 mg/kg and about 4.1-fold (over baseline) at 150 mg/kg [48,49]. If instead, the meal was a bowl of simple broth (consommé), the rise in plasma GLU from the broth alone was 1.5-fold in adults and 1.1-fold in 1-year old infants, and with the addition of 50 mg/kg MSG, was 4.5-fold in adults and 1.8-fold in infants [50,51]. Additionally, the impact on plasma GLU concentrations has been examined in a diurnal study in humans ingesting a normal diet [52].…”

The Roles of Dietary Glutamate in the Intestine

“…Intestinal mucosal tissue is exposed to a high concentration of Glu from the diet and postprandial luminal Glu concentrations can easily be in the order of millimolars, which may accordingly result in a high intramucosal Glu concentration [23]. However, as the gastrointestinal tract has a very high capacity for using Glu, most of the luminal Glu is metabolized within the gut to other amino acids, such as alanine, or utilized as a source of energy within intestinal epithelial cells, and under the usual conditions of intake, the transfer of dietary Glu in the portal vein is low and Glu concentration in peripheral blood is low (10-50 μM) compared to other amino acids [24][25][26].…”

“…Only with high doses of MSG (i.e. >10-12 g), at levels higher than usual human dietary consumption, do systemic blood levels of Glu transiently rise, particularly when ingested without food or if MSG is administered by parenteral routes, and these elevated plasma levels normalize within 2 h after the offset of consumption [24,26,47,48]. The concurrent consumption of sucrose, starch, gelatin, or ingesting MSG with foods, blunts for a part the plasma increase that is reduced by up to several times in relation to an increase in the gut metabolism through transamination of Glu with other metabolites [48][49][50].…”

Executive Summary from the Report: Analysis of Adverse Reactions to Monosodium Glutamate (MSG)

“…Only two published reports evaluated the meta bolic response to ingested glutamate in human in fants (Stegink et al, 1986;Tung and Tung, 1980). As the report by Tung and Tung (1980) contained highly variable data sets in a sample of infants that included two premature infants, the Expert Panel concluded that the study by Stegink et al (1986) contained more useful information.…”