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Fact or Fiction: Examining the Link Between Monosodium Glutamate (MSG) and Headaches


There are plenty of stereotypes when it comes to cultural ethnic foods, one of the most well-known being that Chinese takeout causes headaches. Many people claim to have strong reactions after eating Chinese food, and they claim the culprit is monosodium glutamate, also known as MSG. But on the other side of the debate, is the claim that this belief is rooted in xenophobic and racist thinking. If we delve into the scientific studies, will we find that MSG actually does cause headaches, or not?


Is the claim of MSG and headaches rooted in racist thinking?


The term “Chinese Restaurant Syndrome” (CRS) was first used in the 1960s to describe the reactions some people experienced after eating in Chinese restaurants, including headaches, sweating, heart palpitations, weakness, chest pain, and nausea [1]. It is considered by some to be a racist and prejudiced stereotype. It is also more recently known as the “MSG symptom complex” (MSC), as it was claimed to be a result of eating monosodium glutamate, or MSG, which is commonly used in Chinese restaurants.


What is MSG?


It is a flavor enhancer, largely used in Japanese, Chinese, and South Asian cuisines, contributing an umami taste that intensifies the fatty, meaty flavor of savory dishes [2]. Although its name may give the impression that it is some artificial lab-made chemical, it is actually a salt form of glutamic acid, which is a common amino acid found in nature [1]. Free glutamate can also be found in tomatoes, mushrooms, and parmesan cheese [2]. In 1908, at Tokyo Imperial University, Kikunae Ikeda isolated and crystallized glutamic acid from the seaweed Laminaria japonica, known as kombu, and verified that it was responsible for umami flavor. He called it monosodium glutamate and submitted a patent in order to commercially produce MSG [1].


What do studies show?


Clinical research studies are experiments that are performed on human subjects to determine the safety and efficacy of certain biomedical or behavioral interventions [3], and in this case, the studies would be on the safety and effects of MSG on human subjects. Some of the very first studies that linked MSG to headaches are a matter of debate. They were flawed in many apparent ways, including small sample size, lack of adequate control groups, methodological flaws, lack of dosage accuracy, or usage of extremely high doses far exceeding those unattained in normal diets [4].

Researchers will want to design their studies to have the least amount of flaws possible, and the best way to do that is considered to be randomized double-blind placebo-controlled trials, the “gold standard” of clinical studies. This type of study places the participants into two groups randomly: one group is the experimental treatment group which receives the investigational treatment, and the other group is the control group which receives a placebo. Double-blind means that neither the participants nor the researchers are aware of which treatment is being allocated to them [3]. A placebo is an inert substance or procedure that is used in the control group, as a baseline to use for comparison with the treatment group. For example, a common placebo that clinical researchers will use is a sugar pill, an inert substance to use as a control for comparison with some biomedical treatments in similar pill form [5].

More studies on MSG were done later, using these “gold standard” randomized double-blind strategies, and they found that no differences were detected between the treatment groups and the placebo groups [4]. So far, a causal relationship between MSG and headache has not been scientifically supported by the literature [6]. Reports of MSG hypersensitivity were found to have little supporting evidence, and the connection between MSG and headaches still lacks strong clinical evidence.

Other theories


In these double-blind trials, MSG sensitivity is usually self-assessed and could be affected by placebo response [4]. In this case, it would be considered the nocebo effect, which is the negative version of the placebo effect. In clinical terminology, it is defined as a phenomenon that occurs when a person has negative expectations deriving from the clinical encounter, thus producing negative outcomes [7]. If a person were to have a preconception of the effects of Chinese food, based upon widely known stereotypes, they may begin to exhibit the very symptoms they were dreading.

In addition, other ingredients and additives, such as salt and spices, may play a cumulative role in the effects. This paper, “A review of the Alleged Health Hazards of Monosodium Glutamate,” by Zanfirescu, et al. even questions whether MSG consumption could interfere with the effect of painkillers, as the claims of MSC are linked to nociception, which is the sensation of pain [4]. They are suggesting the possibility that MSG could be causing some indirect alternative effects, through interference with pharmacological drugs.

That same paper suggests that, moving forward, clinical and epidemiological studies should have designs that account for added and natural MSG, to report more accurate data [4]. This suggests that there have not yet been many studies comparing the different types of MSG, and that there could be a possibility that the different types may have different effects.


MSG Classification


The USDA has designated MSG as “generally recognized as safe” (GRAS). The European Union classifies it as a food additive permitted in quantitative limits. MSG is one of the most intensely studied food ingredients and has been found safe, and in fact, it has been placed in the safest category for food additives by the Joint Expert Committee on Food Additives of the United Nations Food and Agriculture Organization and World Health Organization. The USDA concluded that for the CRS symptom complex, MSG as a cause has not been established because the symptom reports are anecdotal [1].


Conclusion


In conclusion, although anecdotal reports suggest that some people may have negative effects on MSG in the form of MSG symptom complex, as of today, monosodium glutamate is considered safe as a flavor additive in its normal quantities. MSG is a naturally occurring substance, and double-blind studies have yet to find conclusive evidence to link MSG with headaches. Although MSG is one of the most intensely studied food ingredients, there are still many aspects of MSG to research in the future, including if MSG has any effects linked to pregnancy, obesity, and cancer [6]. Until then, enjoy in moderation!


Written by Cassandra Legaspi Odulio, BS and edited by Aldrin V. Gomes, PhD


References
  1. Niaz K, Zaplatic E, Spoor J. Effects of Monosodium Glutamate (MSG) on Human Health: A Systematic Review. EXCLI J. 2018 Mar 19;17:273-278.

  2. Bawaskar HS, Bawaskar PH, Bawaskar PH. Chinese Restaurant Syndrome. Indian J Crit Care Med. 2017 Jan;21(1):49-50.

  3. David S, Khandhar PB. Double-Blind Study. [Updated 2022 Jul 18]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK546641/.

  4. Zanfirescu A, Ungurianu A, Tsatsakis AM, Nițulescu GM, Kouretas D, Veskoukis A, Tsoukalas D, Engin AB, Aschner M, Margină D. A review of the alleged health hazards of monosodium glutamate. Compr Rev Food Sci Food Saf. 2019 Jul;18(4):1111-1134.

  5. Gupta U, Verma M. Placebo in clinical trials. Perspect Clin Res. 2013 Jan;4(1):49-52.

  6. Colloca L, Miller FG. The nocebo effect and its relevance for clinical practice. Psychosom Med. 2011 Sep;73(7):598-603.

  7. Wager TD, Atlas LY. The neuroscience of placebo effects: connecting context, learning and health. Nat Rev Neurosci. 2015 Jul;16(7):403-18.

  8. Luana, C. and Barsky. A. J. Placebo and Nocebo Effects. N Engl J Med 2020; 382:554-561

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