Monosodium glutamate or MSG is a much discussed food additive and the subject of studies highlighting possible problems with the cardiovascular system, the gastrointestinal system (1) and the kidneys (2).
Checking the European regulations in Article 9 of Regulation (EU) No. 1169/2011 together with the mandatory requirements of Regulation (EC) 853/2004 for meat preparations, it appears that this additive is not included among the authorised ingredients for the preparation of food meat (3).
 

It may also play a role in the pathology of obesity (4) and in migraine (5).

Glutamate plays an important role in major brain functions including synapse formation and stabilisation, memory, cognition, learning and cell metabolism. However, ingestion of MSG-rich foods can cause different health disorders such as neurotoxicity, hepatotoxicity, obesity and diabetes. The use of medicinal plants and their natural products as therapy against MSG used in the food industry has been suggested as protective. Calendula officinalis, Curcuma longa, Green Tea, Ginkgo biloba and vitamins are some of the main natural products with a protective effect against MSG toxicity mentioned through different mechanisms. This review provides a summary of MSG toxicity and the protective effects of natural products against MSG-induced toxicity (6).

Most relevant studies:

Chakraborty SP. Patho-physiological and toxicological aspects of monosodium glutamate. Toxicol Mech Methods. 2019 Jul;29(6):389-396. doi: 10.1080/15376516.2018.1528649.

Abstract. Nowadays, the life-line of urban population has been formed by commercial foods due to industrialization, urbanization, and rapid increase in working class. Commercial foods are time and energy saving foods but it compromising the nutritional value of foods. The term adulteration refers to the deliberate addition of compound which is usually not present in food. These compounds are known as food additives or food adulterant. Monosodium Glutamate (MSG) is one of the most common food additives. Several studies revealed that MSG has toxic effect on fetal development/fetus, children's, adolescent, and adults. Physiological complication associated with MSG toxicity are hypertension, obesity, gastrointestinal tract troubles, and impairment of function of brain, nervous system, reproductive, and endocrine system. The effect of MSG depends upon its dose, route of administration and exposure time. Public awareness may play a major role in controlling the food adulteration by working in collaboration with National testing facilities to scrutinize each commercial food article from time to time. The aim of this review article is to highlight the deleterious impact of MSG on human health.

Gürgen SG, Sayın O, Çeti N F, Sarsmaz HY, Yazıcı GN, Umur N, Yücel AT. The Effect of Monosodium Glutamate on Neuronal Signaling Molecules in the Hippocampus and the Neuroprotective Effects of Omega-3 Fatty Acids. ACS Chem Neurosci. 2021 Aug 18;12(16):3028-3037. doi: 10.1021/acschemneuro.1c00308.

Abstract. Monosodium glutamate (MSG) is a flavoring substance added to many ready-to-eat foods and has known neurotoxic effects. This study was performed in order to examine the potential toxic effect of MSG on neurons in various regions of the hippocampus in prepubertal rats.....In addition, we concluded that the use of omega-3 fatty acids such as eicosapentaenoic acid and docosahexaenoic acid in addition to Monosodium glutamate may protect against the neurotoxic effects of Monosodium glutamate.

Zhao L, Zhu X, Xia M, Li J, Guo AY, Zhu Y, Yang X. Quercetin Ameliorates Gut Microbiota Dysbiosis That Drives Hypothalamic Damage and Hepatic Lipogenesis in Monosodium Glutamate-Induced Abdominal Obesity. Front Nutr. 2021 Apr 29;8:671353. doi: 10.3389/fnut.2021.671353. 

Abstract. Monosodium glutamate (MSG)-induced abdominal obesity, conventionally caused by hypothalamic damage, is a critical risk factor for health problem. Microbiota-gut-brain axis plays important roles in a variety of metabolic diseases. However, whether gut microbiota is involved in the pathogenesis for MSG-induced abdominal obesity and the effect of quercetin on it remains unclear. Herein, we find that MSG-induced gut microbiota dysbiosis contributes to neuronal damage in the hypothalamus, as indicated by antibiotics-induced microbiota depletion and co-house treatment. Inspired by this finding, we investigate the mechanism in-depth for MSG-induced abdominal obesity. Liver transcriptome profiling shows retinol metabolism disorder in MSG-induced abdominal obese mice. In which, retinol saturase (RetSat) in the liver is notably up-regulated, and the downstream lipogenesis is correspondingly elevated. Importantly, microbiota depletion or co-house treatment eliminates the difference of RetSat expression in the liver, indicating gut microbiota changes are responsible for liver retinol metabolism disorder. Moreover, this study finds dietary quercetin could modulate MSG-induced gut microbiota dysbiosis, alleviate hypothalamic damage and down-regulate liver RetSat expression, thus ameliorating abdominal obesity. Our study enriches the pathogenesis of MSG-induced abdominal obesity and provides a prebiotic agent to ameliorate abdominal obesity. Copyright © 2021 Zhao, Zhu, Xia, Li, Guo, Zhu and Yang.

References_________________________________________________________________________

(1) López-Miranda V, Soto-Montenegro ML, Uranga-Ocio JA, Vera G, Herradón E, González C, Blas C, Martínez-Villaluenga M, López-Pérez AE, Desco M, Abalo R. Effects of chronic dietary exposure to monosodium glutamate on feeding behavior, adiposity, gastrointestinal motility, and cardiovascular function in healthy adult rats. Neurogastroenterol Motil. 2015 Nov;27(11):1559-70. doi: 10.1111/nmo.12653.

 (2) Sharma A  Monosodium glutamate-induced oxidative kidney damage and possible mechanisms: a mini-review. -  J Biomed Sci. 2015 Oct 22;22(1):93. doi: 10.1186/s12929-015-0192-5.

(3) Liuzzo G, Rossi R, Giacometti F, Piva S, Serraino A, Mescolini G, Militerno G. Mislabelling of Döner Kebab Sold in Italy. Ital J Food Saf. 2016 Nov 2;5(4):6149. doi: 10.4081/ijfs.2016.6149.

(4) Shannon M, Green B, Willars G, Wilson J, Matthews N, Lamb J, Gillespie A, Connolly L.  The endocrine disrupting potential of monosodium glutamate (MSG) on secretion of the glucagon-like peptide-1 (GLP-1) gut hormone and GLP-1 receptor interaction. -  Toxicol Lett. 2017 Jan

(5) Zaeem Z, Zhou L, Dilli E. Headaches: a Review of the Role of Dietary Factors. Curr Neurol Neurosci Rep. 2016 Nov;16(11):101. doi: 10.1007/s11910-016-0702-1.

(6) Hajihasani MM, Soheili V, Zirak MR, Sahebkar A, Shakeri A. Natural products as safeguards against monosodium glutamate-induced toxicity. Iran J Basic Med Sci. 2020 Apr;23(4):416-430. doi: 10.22038/IJBMS.2020.43060.10123.