The safety of monosodium glutamate demonstrated in 28-day and 90-day dietary toxicity studies with Sprague-Dawley rats

The commonly used flavor enhancer monosodium glutamate (MSG) has been part of the human diet for many years and has undergone safety evaluation by several international scientific committees and regulatory agencies. Numerous studies exist on MSG but many of these studies are not consistent or representative of how humans are exposed to MSG (i.e., ingestion of food). Two GLP-compliant dietary rodent studies were summarized in evaluations performed by EFSA (2017) and JECFA (2022) but were never published. In the first study, groups of Sprague-Dawley rats (10 rats/sex/group) were fed diets containing 0 ppm (basal diet) or 50,000 ppm MSG for 29 days. In the second study, groups of Sprague-Dawley rats (20 rats/sex/group) were fed diets containing 0 (basal diet), 0.5, 1.5, or 5 % (w/w) MSG for 92–96 days. Animals in both studies underwent clinical examinations, hematology and biochemistry tests, full necropsies, and histopathological examination. No toxicologically significant findings were reported in either study. In the 28-day study, there were no adverse effects observed at 5100 mg/kg bw/day (males) and 4800 mg/kg bw/day (females). In the 90-day study, a no-observed-adverse-effect level (NOAEL) was identified as the highest dose tested of 3170 mg/kg bw/day (males) and 3620 mg/kg bw/day (females) or more.