EXTENSIVE USE OF MONOSODIUM GLUTAMATE: A THREAT TO PUBLIC HEALTH? - EXCLI Journal
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EXCLI Journal 2018;17:273-278 – ISSN 1611-2156
Received: January 23, 2018, accepted: February 28, 2018, published: March 19, 2018
Guest editorial:
EXTENSIVE USE OF MONOSODIUM GLUTAMATE:
A THREAT TO PUBLIC HEALTH?
Kamal Niaz1,*, Elizabeta Zaplatic2, Jonathan Spoor3
1
Department of Pharmacology and Toxicology, Faculty of Bioscience and Agri-Food and
Environmental Technology, University of Teramo-64100, Italy
2
Faculty of Bioscience and Agri-Food and Environmental Technology, University of
Teramo-64100, Italy
3
Erasmus University Medical Centre, Erasmus University Rotterdam, Rotterdam,
the Netherlands
* corresponding author: Kamal Niaz, Department of Pharmacology and Toxicology, Faculty
of Bioscience and Agri-Food and Environmental Technology, University of Teramo, Italy,
Tel # +393207825463, E-mail: kamalniaz1989@gmail.com or kniaz@unite.it
http://dx.doi.org/10.17179/excli2018-1092
This is an Open Access article distributed under the terms of the Creative Commons Attribution License
(http://creativecommons.org/licenses/by/4.0/).
Monosodium Glutamate (MSG) is one of MSG acts on the glutamate receptors and
the most widely used food-additives in releases neurotransmitters which play a vital
commercial foods. Its application has in- role in normal physiological as well as
creased over time and it is found in many pathological processes (Abdallah et al.,
different ingredients and processed foods ob- 2014). Glutamate receptors have three
tainable in every market or grocery store. groups of metabotropic receptors (mGluR)
MSG gives a special aroma to processed and four classes of ionotropic receptors
foods which is known as umami in Japanese. (NMDA, AMPA, delta and kainite recep-
This taste sensation is also called “savoury” tors). All of these receptor types are present
(Xiong et al., 2009). In many countries MSG across the central nervous system. They are
goes by the name “China salt”. Beside its especially numerous in the hypothalamus,
flavour enhancing effects, MSG has been as- hippocampus and amygdala, where they con-
sociated with various forms of toxicity. MSG trol autonomic and metabolic activities (Zhu
has been linked with obesity, metabolic dis- and Gouaux, 2017). Results from both ani-
orders, Chinese Restaurant Syndrome, neu- mal and human studies have demonstrated
rotoxic effects and detrimental effects on the that administration of even the lowest dose
reproductive organs. Table 1 shows products of MSG has toxic effects. The average intake
containing substances that result in the re- of MSG per day is estimated to be 0.3-1.0 g
lease of glutamic metabolites after ingestion. (Solomon et al., 2015). These doses poten-
The purpose of this editorial is to shed light tially disrupt neurons and might have ad-
on MSG toxicity and the possible threat it verse effects on behaviour. Animal studies
poses to public health. Can MSG associated have demonstrated that neonatal MSG con-
harm be prevented or should the product be sumption sets a precedent for the develop-
banned altogether? ment of obesity later on. Insulin resistance
273EXCLI Journal 2018;17:273-278 – ISSN 1611-2156
Received: January 23, 2018, accepted: February 28, 2018, published: March 19, 2018
and reduced glucose tolerance in rodents due study, the authors were able to demonstrate
to MSG consumption raise concerns about that MSG induces a significant decrease in
the development of obesity in MSG consum- liver transaminases indicating hepatic dam-
ing humans. The same study revealed that age. This damage was likely the result of
MSG intake causes a disrupted energy bal- non-alcoholic steatohepatitis which is asso-
ance by increasing the palatability of food ciated with long lasting inflammation. MSG
and disturbing the leptin-mediated hypothal- was not reported to have any effect on hun-
amus signalling cascade, potentially leading ger. There are reports though of gastric dis-
to obesity (Araujo et al., 2017; He et al., tention caused by MSG two hours after in-
2011). In a study into the inflammatory pro- gestion. Also changes in important parame-
file of MSG induced obesity, it has been ters, particularly concentrations of amino ac-
shown that MSG triggers micro-RNA ids, have been noted. Leurine, isoleucine, va-
(mRNA) expression of interleukin-6 (IL-6), line, lysine, cysteine, alanine, tyrosin and
tumour necrosis factor-alpha (TNF-α), resis- tryptophan were significantly higher in pig
tin and leptin in visceral adipose tissue. This blood samples after MSG consumption com-
in turn leads to enhanced insulin, resistin and pared to controls. No changes have been ob-
leptin concentrations in the circulation and served in the postprandial glucose and insu-
ultimately an impaired glucose tolerance lin levels after intake of food supplemented
(Roman‐Ramos et al., 2011). In the same with MSG (Kong et al., 2015).
Table 1: Different sources of MSG in commercial products
Ingredients containing Ingredients containing Ingredients that trigger
free glutamic acid MSG MSG-toxicity in sensitive
individuals
-Glutamic acid (E 620) -Carrageenan (E 407) -Corn starch
-Glutamate (E620) -Bouillon and broth -Corn syrup
-Monopotassium glutamate (E 622) -Stock -Modified food starch
-Calcium glutamate (E 623) -Flavouring products -Lipolyzed butter fat
-Monoammonium glutamate (E 624) -Natural flavour -Dextrose
-Magnesium glutamate (E 625) -Maltodextrin -Rice syrup
-Natrium glutamate -Oligodextrin -Brown rice syrup
-Hydrolysed protein -Citric acid, Citrate (E 330) -Milk powder
-Calcium caseinate -Ultra-pasteurized products -Reduced fat milk
-Sodium caseinate -Barley malt (skim; 1 %; 2 %)
-Yeast extract -Malted barley -Low fat products
-Torula yeast -Brewer’s yeast -Vitamin enriched products
-Yeast food -Pectin (E 440) -Vinegar
-Yeast nutrient -Malt extract -Specific amino acid chelates
-Autolyzed yeast -Seasonings such as citrate, aspartate
-Gelatin and glutamate act as chelat-
-Textured protein ing agents with minerals
-Whey protein and other related supplements
products
-Soy protein and other products
-Fortified protein
-Fermented foods
-Protease
-Vetsin
-Ajinomoto
-Umami
E: European numbering system for registered food-additives
274EXCLI Journal 2018;17:273-278 – ISSN 1611-2156
Received: January 23, 2018, accepted: February 28, 2018, published: March 19, 2018
The term “Chinese restaurant syndrome” established that MSG has some laudable gus-
(CRS) was first used more than four decades tatory and psychological effects as well as
ago. At the onset of symptoms patients expe- positive effects with regard to hypertension
rience complaints such as a burning sensa- and iron deficiency. However, at the same
tion at the back of the neck, blistering on time there are abundant reports of harmful
both arms and occasionally on the anterior effects such as oxidative stress, DNA dam-
thorax, general weakness, fatigue and palpi- age, protein modification and lysis of stro-
tations. These symptoms occur 20 minutes mal cells (Mustafa et al., 2017).
after consumption of a meal rich in MSG One of the most extreme examples of
(Bawaskar et al., 2017). Other symptoms negative effects attributed to MSG concerns
that may appear later include flushing, dizzi- asthma. A connection between asthma and
ness, syncope and facial pressure. In a study the consumption of MSG could however
that explored negative dietary effects of never be convincingly proven. In ovalbumin-
MSG, double blind and placebo-controlled induced asthma models fed with 0.5 % and
trails were performed in which the admin- 5 % MSG, no influence was reported on eo-
istration of MSG, doses ranging from 57 to sinophil infiltration, TH-2 cytokines and
150 mg/kg, was compared with the admin- immunoglobulin E (IgE) levels in the pul-
istration of a dose of 24 mg/kg NaCl. MSG monary circulation. Neither was there a
as well as NaCl administration resulted in measurable effect on airway hyper respon-
muscle pain and/or changes in mechanical siveness (Shi et al., 2012b; Zhou et al., 2012;
sensitivity. MSG administration however Yoneda et al., 2011). Injection of MSG led
was also associated with headache and ten- to bradycardia, enhanced mean blood pres-
derness of the pericranial muscles. Further- sure and reduced heart rate variability. It also
more, administration of a high dose of more resulted in vagal and sympathetic effect not
than 75 mg/kg MSG significantly elevated measurable in controls (Konrad et al., 2012).
systolic blood pressure (Obayashi and A study on a human model revealed that
Nagamura, 2016; Shimada et al., 2015). It is MSG consumption and haemoglobin levels
not well understood if MSG is correlated are positively related to each other due to
with complex cases of CRS (Kazmi et al., leptin’s vital role in haematopoiesis (Shi et
2017). al., 2012a). Other studies have indicated
Both animal models and human studies however that beside MSG’s stimulation,
have shown toxic effect of MSG on the re- there might be other mechanisms which dis-
productive system. Administration of MSG rupt normal physiological function of
at a dose of 2 mg/g during various perinatal haematopoiesis. Further research should be
periods of life leads to an increased number carried out to explore the relationship be-
of pachytene stage cells among the primary tween nutritional intake of MSG and such-
spermatocytes compared to controls in sper- like physiological mechanisms. A promising
matogenesis (Mondal et al., 2017). MSG recent discovery indicates that α-
causes disruption of stroma cell vacuolations ketoglutarate dehydrogenase, glutamate re-
and basement membrane- and cellular hyper- ceptors and cysteine-glutamate antiporters
trophy of the theca folliculi in the ovaries. have a potential role in upregulation of oxi-
These processes of atrophy and degeneration dative stress in MSG-inducted toxicity
were assessed under different dosages (Dong (Sharma, 2015).
and Robbins, 2015). It has been well-
275EXCLI Journal 2018;17:273-278 – ISSN 1611-2156
Received: January 23, 2018, accepted: February 28, 2018, published: March 19, 2018
Figure 1: MSG toxicity leads to different disorders
The harmful effects of MSG described in curcumin in the amelioration of cognitive
this paper might be perceived only by a damage via stabilisation of acetyl cholines-
small number of scientists, but they represent terase (AchE) levels and reduction of TNF-α.
a silent threat posed by the consumption of Furthermore, curcumin acts as a protective
this popular additive to all of society. It has agent against neural damage due to its effect
been suggested that toxicity of MSG can be of decreasing the expression of mGLUR5
overcome by the use of certain kinds of vit- and N-Methyl-D-aspartate receptors 2B
amin like A, C, D and E. Quercetin and dilti- (NMDA2B) in the hippocampus. Because of
azem have also been suggested to play a pro- its properties that help balance glutamate
tective role in MSG-induced toxicity levels scientists have suggested the introduc-
(Mustafa et al., 2017). Vitamin A and C have tion of combinations of curcumin and MSG
been shown to protect nerve cells and cere- in the market (Khalil and Khedr, 2016).
bral cortex in male albino rat models. The In conclusion we would like to state that
supplementation of vitamin D and E in although MSG has proven its value as an en-
MSG-induced oxidative stress led to de- hancer of flavour, different studies have
creased lipid peroxidation, catalase and su- hinted at possible toxic effects related to this
peroxide dismutase in the liver. It also im- popular food-additive. These toxic effects
proved levels of glutathione. Quercetin has include CNS disorder, obesity, disruptions in
been proven to reduce glucose, leptine and adipose tissue physiology, hepatic damage,
creatinine levels, which in turn enhances su- CRS and reproductive malfunctions. These
peroxide dismutase and glutathione peroxi- threats might have hitherto been underesti-
dase, while diltiazem protects against mor- mated. In the meantime, people keep using
phological functional disorders. Further- ever larger amounts of MSG unaware of the
more, new research explores the function of possible consequences. Further studies need
276EXCLI Journal 2018;17:273-278 – ISSN 1611-2156
Received: January 23, 2018, accepted: February 28, 2018, published: March 19, 2018
to be undertaken in order to assess the con- Kazmi Z, Fatima I, Perveen S, Malik SS. Mono-
nection between MSG and cardiovascular sodium glutamate: Review on clinical reports. Int J
Food Properties. 2017;1807-15.
disorders, headache, and hypertension in
human models. MSG is a controversial Khalil RM, Khedr NF. Curcumin protects against
food-additive used in canned food, crackers, monosodium glutamate neurotoxicity and decreasing
meat, salad dressings, frozen dinners and a NMDA2B and mGluR5 expression in rat hippo-
campus. Neurosignals. 2016;24:81-7.
myriad of other products. It is found in local
supermarkets, restaurants and school cafete- Kong X, Zhou X, Feng Z, Li FN, Ji YJ, Tan B, et al.
rias alike. While MSG probably has huge Dietary supplementation with monosodium L-gluta-
benefits to the food industry, the ubiquitous mate modifies lipid composition and gene expression
use of this food-additive could have negative related to lipid metabolism in growing pigs fed a
normal-or high-fat diet. Livest Sci. 2015;180:247-52.
consequences for public health. If more sub-
stantive evidence of MSG-toxicity would be Konrad SP, Farah V, Rodrigues B, Wichi RB,
provided, a total ban on the use of MSG as a Machado UF, Lopes HF, et al. Monosodium gluta-
flavour enhancer would not be unwise to mate neonatal treatment induces cardiovascular
autonomic function changes in rodents. Clinics (Sao
consider. Paulo). 2012; 67:1209-14.
Conflict of interest Mondal M, Sarkar K, Nath PP, Paul G. Monosodium
There is no conflict of interest. glutamate suppresses the female reproductive function
by impairing the functions of ovary and uterus in rat.
Environ Toxicol. 2017;33:198-208.
Acknowledgements
The authors who worked on this manu- Mustafa Z, Ashraf S, Tauheed SF, Ali S. Mono-
script acknowledge their respective universi- sodium glutamate, commercial production, positive
ties and institutes. and negative effects on human body and remedies - a
review. IJSRST. 2017;3:425-35.
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