Monosodium glutamate: Breaking the stigma with a fresh look at an old kitchen flavor, and its new role in modern culture

Monosodium glutamate, otherwise known as MSG, is a sodium salt of the naturally occurring amino acid, L-glutamic acid (the primary form in commercial manufacture) or glutamate (anion form of glutamic acid) (PubChem, n.d.). One of the most abundant non-essential amino acids, key component in protein chains of every living organism, as well as a vital component in neuro messaging. in this post we review its discovery and how now is making a comeback to modern cooking by the hand of famous chefs.

Outside of its role in the human body as an amino acid. Glutamate has been part of other culture’s diet for thousands of years. In fact, glutamate was not initially discovered as a primary amino acid. 

Its history as a kitchen flavor started in 1866, when the german chemist Karl Heinrich Ritthausen was studying the proteome ¹the protein content of cells, tissues, and organisms of wheat gluten within a solution of alcohol and water (Vickery & Schmidt, 1931). Glutamic acid crystal was discovered by treating wheat with sulfuric acid (Vickery & Schmidt, 1931; Yamaguchi & Ninomiya, 1998). It was a hydrolysis reaction between gluten, a protein in wheat, and the acid, resulted in glutamate salt as we know it (Vickery & Schmidt, 1931; Yamaguchi & Ninomiya, 1998). However, he did not explore the salt crystals any further and only mentioned that it had a faint acidic taste (Yamaguchi & Ninomiya, 1998). After that, MSG returned again to the shadows. 

In nature, glutamate is widely available as one of the primary amino acids in cellular biochemistry. This amino acid is a crucial player in the nitrogen metabolism pathway where excess nitrogen would be converted into ammonia; that the human body would then discard in urine. (Hubbard & Binder, 2016)

MSG through history: From dashi ²basic soup stock used in Japanese cooking to MSG

Although being discovered in 1866, glutamate was not yet known for its current flavor enhancing profile, despite the fact that ingredients with high glutamate content have been used for a long time.  

As part of cooking, it can be often found in large amounts, in fermented foods (Otsuka, 1998; Tamang et al., 2010; Yamaguchi & Ninomiya, 1998; Yoshida, 1998). Traditionally, among fermented foods, fish sauce and paste, contain a high amount of free glutamate. Their usage has been shown to be spanning around the globe from the Ancient Roman and Greek to the first official record of usage in Asian cuisine in the 2^nd century B.C. (Yoshida, 1998). It has been speculated that the taste enhancer effect of fish sauce was discovered from an accidentally fermented salted fish mixture where it was found to be an acceptable complementary condiment to the traditional food (Tamang et al., 2010).

Pre-commercial production

In spite of having such a long history in many civilizations cuisine, the taste profile of glutamate was only defined by Professor Kikunae Ikeda at the Imperial University of Tokyo in 1907 (Yamaguchi & Ninomiya, 1998). The compound was isolated as the major tasting component of kombu broth or dashi, a stock made from boiling dried kelp (Osawa, 2012). It was noticed that the compound contributed with a distinctly different taste other than that of the currently defined basic tastes (sweet, salty, sour and bitter) (Yamaguchi & Ninomiya, 1998) . Ikeda gave the taste profile the name “Umami” (Yamaguchi & Ninomiya, 1998). The word according to the Oxford dictionary literally means deliciousness in Japanese.

Since glutamate is not just a compound found in kelp, a student of Ikeda later also identified glutamate providing the same taste profile in dried skipjack ³a species of tuna fish together with other compounds with umami tasting characteristics (Yamaguchi & Ninomiya, 1998). So far, we have discovered several compounds like L-aspartic acid and succinic acid, tartaric acid and lactic acid with similar taste profile as that of glutamate (Suess et al., 2015). The effectiveness of MSG flavor can be improved even more when used in presence of compound like guanosine or inosine 5′-monophosphate (Suess et al., 2015).

The umami taste profile: How do humans taste the umami flavor

Umami, the taste of dashi that Ikeda noted for glutamate, is the flavor enhancing effect created by the compound. It has been noted that while the current flow of ions and changing of ion channel conductance create the neurological response to salty and sour flavor, umami, sweet and bitter interact through activation of G-protein coupled receptors (Lindemann, 2000). A study published in 2000 showed that, for umami flavor specifically, glutamate interacts with the nervous system through a truncated version of the mGluR4 glutamate receptor (Lindemann, 2000). mGluR4 exists in the brain and is responsible for modulating the expression of the neuro messenger cAMP (Lindemann, 2000). The study suggested that umami can be the result of a combination of a large number of cellular sustained hyperpolarization and a small amount of transient depolarization responses of taste bud cells (Lindemann, 2000).

DID YOU KNOW:

A loanword from the Japanese(うま味), umami can be translated as “pleasant savory taste.” This neologism was coined in 1908 by Japanese chemist Kikunae Ikeda from a nominalization of umai (うまい) “delicious.” The compound 旨味 (with mi (味) “taste”) is used for a more general sense of a food as delicious.

Ikeda suggested that the origin of how human had evolved this ability for detection of glutamate, and  to differentiate the umami flavor from other flavor profiles is directly related to the ability of humans to identify readily accessible and protein rich food (Mouritsen & Styrbæk, 2014). Due to the large energy requirement for supporting a large brain, this particular ability also likely to contribute to the human evolution toward expanding our brain size (Williams & Hill, 2017). Despite its taste being much more subtle than salt, he also noted that our palate sensitivity to glutamate is ten times greater than that of salt (Mouritsen & Styrbæk, 2014). In usage, Ikeda also observed that glutamate can amplify our sensitivity to salt (Mouritsen & Styrbæk, 2014). This has also made glutamate extremely attractive to the processed food industry as a food additive (Maluly et al., 2017). Making possible to perceive food to be  saltier than it should be with the same or less amount of sodium chloride or salt (Maluly et al., 2017).

The MSG controversy, when racism mixes with food

The restaurant industry, especially Chinese restaurants, are also big supporters of the usage of glutamate in cooking (Mouritsen & Styrbæk, 2014). This has led to a cultural association in Western society between the usage of glutamate and Chinese restaurants (Mouritsen & Styrbæk, 2014). Stemming from the same association was also the phenomenon known as the “Chinese restaurant syndrome” where a certain temporary hypersensitivity condition supposedly caused by eating food that was thought to be containing high amounts of MSG at Chinese restaurants. Originally the syndrome was described in a letter to the editor of The New England Journal of Medicine in the 1960s by Dr. Robert Ho Man Kwok. He mentioned the syndrome vaguely with symptoms including gradually radiating numbness, heart palpitations and thirst 15 to 20 minutes after consumption of the dish. He suggested a possible connection between the excessive combination of MSG and table salt. This was the beginning of the controversy that is still going on today.

DID YOU KNOW: 

Dr. Kwok in an interview with This American Life was revealed to be Dr. Howard Steel, a caucasian professor from the University of Maryland. However, the New England Journal of Medicine has yet to acknowledge that Dr. Howard Steel was the person who pen and sent the letter. The letter was sent due to a $10 dollar bet with a friend to see if he could be published in NEJM. He wrote the letter and rather than signing using his name, he choose Ho Man Kwok (an offensive pun for human crock). The doctor was horrified that the letter was published and unsuccessfully tried to get it retracted. Dr. Steel also tried to talk to many but none believe him that it was just a joke. (“668: The Long Fuse”, 2019)

One of the most common complaints against MSG is that it can induce a feeling of thirst. While this could certainly be caused by the sodium within MSG, the amount of MSG (0.2 – 0.8% by weight in food) (Rogers, 2015) is often a lot smaller in comparison to salt (1.8% by weight in deep crispy pizza) (“How much salt are you eating?”, n.d.) which are one of the main sodium contributors. Since the effect of MSG can cause food to actually taste saltier than it should, the food one is eating should contain even less salt than equivalent of one serving without MSG. MSG has yet to be shown to have effects on thirst. These thirsty urges could simply be from the high sodium chloride, or salt, content of Chinese food rather than MSG.

Many studies have been carried out on animal models such as rats for potential negative physiological and neurological effects of MSG (Hashem et al., 2012; Sharma et al., 2014). Many reviews however have also pointed out that due to the difference in glutamate metabolism of humans and the model animals, as well as the usage of glutamate often as food additive rather than direct consumption, many of the links to potential negative effects in humans in these studies are unclear (Beyreuther et al., 2007; Rogers, 2015; Zanfirescu et al., 2019). Studies in humans have so far shown no significant danger of MSG used as food additive to non-glutamate sensitive individuals (Zanfirescu et al., 2019). Therefore, the status of MSG as a safe food additive is still maintained by the FDA since 1958 and other international/national agencies and organizations.

DID YOU KNOW:

In rat neurological function, a recent study in 2014 studied a potential relationship between MSG and Alzheimer’s disease (Dief et al., 2014). The MSG treated rats were either consuming MSG solution of 10% orally a total amount of 2 g/kg body weight or provided with injection of 10% MSG solution with 4 g/kg body weight daily. The research was based on the idea that cerebral glutamate can cause neuronal shrinkage and apoptosis. However, the research has also found that no change in the glutamate content within the brain was detected in both treatments with oral and subcutaneous MSG. Even though there has been association between cyclic AMP-protein kinase and glutamate, without a clear cerebral glutamate response, the conclusion of the article linking glutamate to the increase in cyclic AMP-protein kinase is not straight forward (Rogers, 2015). 

Despite the controversy, MSG is still been used widely across the world without any problems. Glutamic acid being one of the most abundant non-essential amino acids of life, while glutamate is a vital component in neuro messaging (Briguglio et al., 2018; Lindemann, 2000), sensitivity or allergy to MSG from food is likely to be impossible. The symptoms related to the allegedly MSG allergy described as the “Chinese restaurant syndrome” can also be caused by consumption of too much sodium chloride, otherwise known as salt. Much of the current aversion altitude in western society to MSG despite advocated for by some of the most famous professional chefs has been suggested to not be from the supposed allergy but rather from possible underlying cultural sentiment against the exotic fast food (Mosby, 2009). In a report by 538, professor Brendan Nyhan of Dartmouth pointed out a possible cause that people just involuntarily association of bad feeling after eating Chinese food with MSG without investigating the actual causes (“How MSG Got A Bad Rap: Flawed Science And Xenophobia”, n.d.) . These conclusions, once made, would be very hard to be replaced despite the availability of information that proves otherwise.

Glutamic acid being one of the most abundant non-essential amino acids of life, while glutamate is a vital component in neuro messaging (Briguglio et al., 2018; Lindemann, 2000), sensitivity or allergy to MSG from food is likely to be impossible.

Furthermore, even though the compound is widely used in the western processed food industry, known as additive 620 or 621 (“MSG in food”, n.d.), the term MSG seems to carry a special stigma toward eastern cuisine (Mosby, 2009). This stigma could be observed through much of the reactions to “Chinese restaurant syndrome” at the time when “Dr. Kwok’s” letter was released focusing only on Chinese restaurants, describing their food with sneaky and hidden MSG (Mosby, 2009). There were campaigns demanding MSG usage should be limited not only in Chinese food but in other cuisines (Mosby, 2009). These sentiments were further amplified by the thought that, within Chinese cuisine, there were possible unproven consumption of meat that was deemed deviant and that MSG was used to hide it (Mosby, 2009). By appealing to the underlying fear and racial bias, with only inconclusive and anecdotal evidence, the ideas that MSG and in turn Chinese cooking should be avoided are still pervasive nowadays despite the compound being championed by celebrity chefs of modern cuisine like Heston Blumenthal and Grant Achatz.

While chef Blumenthal was uncertain about the healthiness of the common salt, he opposes the negative press of MSG (Malnick, 2014). At Cheltenham Literature Festival, he said that the compound is important to our taste buds and should not be ignored (Malnick, 2014). In an interview with Tasting Table, chef Achatz who traveled with his own stash of MSG powder was also confident of the role of MSG in good food, mentioning that “It’s really no different than, say, using nitrates to cure sausage or pink salt to preserve boudin blanc.” (“Grant Achatz and MSG”, 2013)

For the Asian chefs who have been growing up eating home cook meal with MSG, the idea that MSG causing serious health problems is totally nonsense. As chef Roy Choi had to say, “I grew up on it by the buckets. Go to any Asian home: It’s there next to the sugar and salt. It’s a flavor that’s ingrained in my soul.” (“Grant Achatz and MSG”, 2013). And one of the most vocal supporters of MSG, chef David Chang, has to say about the important of MSG in cooking, “It’s the MSG. That’s why everyone is so enamoured with Asian flavours. It has that punch that we don’t find in other foods.” (Akhtar, 2013)

So, to finish this fresh new look at MSG, it can be concluded that with no direct evidence of health-related problems stemming from MSG as food flavor enhancer, the scientific consensus is that MSG is safe in the way it is currently being used for human consumption as 0.2-0.8% in weight of food. In fact, monosodium glutamate (MSG) can be used to reduce your consumption of sodium chloride (table salt) in foods while you cook (Maluly et al., 2017), while adding a fabulous umami flavor to your dishes. So there you go! Another positive to this amino acid salt!

References

668: The Long Fuse. (2019, February 16). This American Life. https://www.thisamericanlife.org/668/transcript

Akhtar, K. (2013, December 9). MSG finding its way back to restaurant menus. CBC. https://www.cbc.ca/news/canada/msg-finding-its-way-back-to-restaurant-menus-1.2457140

Beyreuther, K., Biesalski, H. K., Fernstrom, J. D., Grimm, P., Hammes, W. P., Heinemann, U., Kempski, O., Stehle, P., Steinhart, H., & Walker, R. (2007). Consensus meeting: Monosodium glutamate – an update. European Journal of Clinical Nutrition, 61(3), 304–313. https://doi.org/10.1038/sj.ejcn.1602526

Briguglio, M., Dell’Osso, B., Panzica, G., Malgaroli, A., Banfi, G., Zanaboni Dina, C., Galentino, R., & Porta, M. (2018). Dietary Neurotransmitters: A Narrative Review on Current Knowledge. Nutrients, 10(5). https://doi.org/10.3390/nu10050591

Chinese-Restaurant Syndrome. (1968). New England Journal of Medicine, 278(14), 796–796. https://doi.org/10.1056/NEJM196804042781419

Dief, A. E., Kamha, E. S., Baraka, A. M., & Elshorbagy, A. K. (2014). Monosodium glutamate neurotoxicity increases beta amyloid in the rat hippocampus: A potential role for cyclic AMP protein kinase. NeuroToxicology, 42, 76–82. https://doi.org/10.1016/j.neuro.2014.04.003

Grant Achatz and MSG. (2013, December 6). Tasting Table. https://www.tastingtable.com/cook/national/Grant-Achatz-and-MSG

Hashem, H. E., El-Din Safwat, M. D., & Algaidi, S. (2012). The effect of monosodium glutamate on the cerebellar cortex of male albino rats and the protective role of vitamin C (histological and immunohistochemical study). Journal of Molecular Histology, 43(2), 179–186. https://doi.org/10.1007/s10735-011-9380-0

How MSG Got A Bad Rap: Flawed Science And Xenophobia | FiveThirtyEight. (n.d.). Retrieved December 22, 2019, from https://fivethirtyeight.com/features/how-msg-got-a-bad-rap-flawed-science-and-xenophobia/

How much salt are you eating? (n.d.). Retrieved December 20, 2019, from https://www.safefood.eu/How-much-salt-are-you-eating

Hubbard, J. A., & Binder, D. K. (2016). Chapter 9—Glutamate Metabolism. In J. A. Hubbard & D. K. Binder (Eds.), Astrocytes and Epilepsy (pp. 197–224). Academic Press. https://doi.org/10.1016/B978-0-12-802401-0.00009-0

Lindemann, B. (2000). A taste for umami. Nature Neuroscience, 3(2), 99–100. https://doi.org/10.1038/72153

Malnick, E. (2014, October 12). Heston Blumenthal says idea MSG is bad for you is “old wives tale.” https://www.telegraph.co.uk/foodanddrink/foodanddrinknews/11156357/Heston-Blumenthal-says-idea-MSG-is-bad-for-you-is-old-wives-tale.html

Maluly, H. D. B., Arisseto‐Bragotto, A. P., & Reyes, F. G. R. (2017). Monosodium glutamate as a tool to reduce sodium in foodstuffs: Technological and safety aspects. Food Science & Nutrition, 5(6), 1039–1048. https://doi.org/10.1002/fsn3.499

Mosby, I. (2009). ‘That Won-Ton Soup Headache’: The Chinese Restaurant Syndrome, MSG and the Making of American Food, 1968–1980. Social History of Medicine, 22(1), 133–151. https://doi.org/10.1093/shm/hkn098

Mouritsen, O., & Styrbæk, K. (2014). Umami, Unlocking the Secrets of the Fifth Taste. Columbia University Press. https://doi.org/10.7312/mour16890

MSG in food. (n.d.). Retrieved January 19, 2020, from https://www.foodstandards.gov.au/consumer/additives/msg/Pages/default.aspx

Osawa, Y. (2012). Glutamate Perception, Soup Stock, and the Concept of Umami: The Ethnography, Food Ecology, and History of Dashi in Japan. Ecology of Food and Nutrition, 51(4), 329–345. https://doi.org/10.1080/03670244.2012.691389

Otsuka, S. (1998). Umami in Japan, Korea, and Southeast Asia. Food Reviews International, 14(2–3), 247–256. https://doi.org/10.1080/87559129809541159

PubChem. (n.d.). Glutamic acid. Retrieved January 19, 2020, from https://pubchem.ncbi.nlm.nih.gov/compound/33032

Rogers, M. D. (2015). Commentary on “Monosodium glutamate neurotoxicity increases beta amyloid in the rat hippocampus: A potential role for cyclic AMP protein kinase” (Dief et al., 2014). NeuroToxicology, 50, 179–180. https://doi.org/10.1016/j.neuro.2015.06.003

Sharma, A., Wongkham, C., Prasongwattana, V., Boonnate, P., Thanan, R., Reungjui, S., & Cha’on, U. (2014). Proteomic analysis of kidney in rats chronically exposed to monosodium glutamate. PLoS ONE, 9(12), e116233. https://doi.org/10.1371/journal.pone.0116233

Suess, B., Festring, D., & Hofmann, T. (2015). 15—Umami compounds and taste enhancers. In J. K. Parker, J. S. Elmore, & L. Methven (Eds.), Flavour Development, Analysis and Perception in Food and Beverages (pp. 331–351). Woodhead Publishing. https://doi.org/10.1016/B978-1-78242-103-0.00015-1

Tamang, J. P., Kailasapathy, K., & Kailasapathy, K. (2010). Fermented Foods and Beverages of the World. CRC Press. https://doi.org/10.1201/EBK1420094954

Vickery, H. Bradford., & Schmidt, C. L. A. (1931). The History of the Discovery of the Amino Acids. Chemical Reviews, 9(2), 169–318. https://doi.org/10.1021/cr60033a001

Williams, A. C., & Hill, L. J. (2017). Meat and Nicotinamide: A Causal Role in Human Evolution, History, and Demographics. International Journal of Tryptophan Research : IJTR, 10. https://doi.org/10.1177/1178646917704661

Yamaguchi, S., & Ninomiya, K. (1998). What is umami? Food Reviews International, 14(2–3), 123–138. https://doi.org/10.1080/87559129809541155

Yoshida, Y. (1998). Umami taste and traditional seasonings. Food Reviews International, 14(2–3), 213–246. https://doi.org/10.1080/87559129809541158

Zanfirescu, A., Ungurianu, A., Tsatsakis, A. M., Nițulescu, G. M., Kouretas, D., Veskoukis, A., Tsoukalas, D., Engin, A. B., Aschner, M., & Margină, D. (2019). A Review of the Alleged Health Hazards of Monosodium Glutamate. Comprehensive Reviews in Food Science and Food Safety, 18(4), 1111–1134. https://doi.org/10.1111/1541-4337.12448