Effects of monosodium glutamate on human health: A systematic review

Abstract

Monosodium glutamate (MSG) is one of several forms of glutamic acid found in foods, in large part because glutamic acid (an amino acid) is pervasive in nature. MSG is used in the food industry as a flavor enhancer with an umami taste that intensifies the meaty, savory flavor of food, as naturally occurring glutamate does in foods such as stews and meat soups. MSG has been used for more than 100 years to season food, with a number of studies conducted on its safety. Under normal conditions, humans can metabolize relatively large quantities of glutamate, which is naturally produced in the gut by exopeptidase enzymes in the course of protein hydrolysis. The median lethal dose (LD₅₀) is between 15 and 18 g/kg body weight in mice and rats, respectively, five times greater than the LD₅₀ of salt (3 g/kg in rats). The use of MSG as a food additive and the natural level of glutamic acid in foods are not toxicological concerns in humans. The U.S. Food and Drug Administration have given MSG it’s generally recognized as safe (GRAS) designation. A popular belief is that large doses of MSG can cause headaches and other feelings of discomfort, known as ‘Chinese Restaurant Syndrome’ (CRS), but double-blind tests fail to find evidence of such a reaction. The European Union classifies it as a food additive permitted in certain foods and subject to quantitative limits.