We usually go to Chinatown for lunch since it’s just a 10-15 minute walk from campus. Not only are the restaurants reasonably priced compared to the other lunch options available nearby, but there is a lot of variety as well. There is of course Chinese food like dumplings or bbq pork/chicken/duck on rice but also Japanese staples like sushi and ramen, Korean favourites like chigae and bibimbap, and Vietnamese classics like phở and bún. But regardless of where I ate, I would often get headaches an hour or two after lunch.
I have heard of my friend complain about her “MSG Headches” in the past, but I had just assumed that “MSG headaches” were just another example of sensationalized scientific facts. Then I came across a nutritional science textbook describing MSG sensitivity, and I began to wonder if I had just been ignorant about the health implications of consuming MSG.
What is MSG?
As discussed in (“Are you tasting saltiness, sweetness, sourness, or bitterness?”), umami is a basic taste that resembles meaty and savoury flavours. Dr. Kikuna Ikeda, a professor at Tokyo Imperial University, first identified this unique taste in 1908 after isolating glutamic acid to be the source of the savoury flavour found in Japanese stock prepared from konbu seaweed. Subsequently, Dr. Ikeda and entrepreneur Saburosuke Suzuki patented the industrial production of monosodium L-glutamate (MSG). This involved isolating and purifying L-glutamic acid hydrochloride from vegetable proteins that were treated with hydrochloric acid  .
L-glutamic acid is an amino acid that exists in free and protein-bound form. But it is the free glutamic acid that produces the savoury, flavour enhancing properties . Free glutamic acid occurs naturally in a variety of foods including chicken (22 mg per 100 g), scallop (140 mg per 100 g), kelp (1608 mg per 100 g), parmegiano (1680 mg per 100 g), and tomato (246 mg per 100 g) . Glutamates are the salt derivatives of glutamic acid and can be synthesized to produce the savoury flavours of glutamic acid. MSG is simply the the amino acid glutamic acid bound to sodium, and serves as as a flavor enhancer for the same purposes as free glutamic acid. Interestingly, glutamate in commercial products such as MSG is not different from naturally occurring glutamate .
What is MSG sensitivity, and how serious is it?
The so-called “Chinese Restaurant Syndrome”, also referred by the the less pejorative “MSG symptom complex”, was linked to adverse reactions in some people after consuming Chinese food containing MSG. These symptoms included: burning sensation of the back of the neck, forearms and chest; facial pressure/tightness; chest pain; headache; nausea; upper body tingling/weakness; palpitation; numbness in the back of the neck, arms and back; bronchospasm (in asthmatics only); drowsiness .
Since the first report of “Chinese Restaurant Syndome” in 1968 , subsequent reports on the possible connection between MSG and the symptoms of the “MSG symptom complex” have shown mixed results . Williams and Woessner (2009) cited three double-blind (i.e. subjects and investigators don’t know who is in which group), placebo-controlled (DBPC) studies published in the 1970s found no connection between MSG consumption and MSG symptom complex in healthy volunteers. However, they cited a DBPC study published in the late 1990s that reported a signiﬁcant increase in the frequency of symptoms associated with MSG in self-identiﬁed MSG-sensitive subjects . Finally the largest study to date involving 130 self-identiﬁed MSG sensitive subjects reported that adverse MSG reactions were not consistent or reproducible .
It has been reported that healthy individuals can experience manifestations of the MSG symptom complex after consuming >3 g of MSG without food . On the other hand, adverse reactions were not reported when MSG was ingested with food, and MSG is generally a safe food flavouring additive . Furthermore, a typical serving of food only contains about 0.5 mg of MSG . So with that in mind, if you have these symptoms after ingesting MSG, don’t worry you’re not alone. But currently, it’d seem that MSG sensitivity is more in your head …
 Sano C (2009). History of glutamate production. The American journal of clinical nutrition, 90 (3) PMID: 19640955
 Jinap, S., & Hajeb, P. (2010). Glutamate. Its applications in food and contribution to health Appetite, 55 (1), 1-10 DOI: 10.1016/j.appet.2010.05.002
 Walker R, & Lupien JR (2000). The safety evaluation of monosodium glutamate. The Journal of nutrition, 130 (4S Suppl) PMID: 10736380
 R.H.M Kwok (1968). Chinese-restaurant syndrome N. Engl. J. Med., 278
 Williams, A., & Woessner, K. (2009). Monosodium glutamate ‘allergy’: menace or myth? Clinical & Experimental Allergy, 39 (5), 640-646 DOI: 10.1111/j.1365-2222.2009.03221.x
 Geha RS, Beiser A, Ren C, Patterson R, Greenberger PA, Grammer LC, Ditto AM, Harris KE, Shaughnessy MA, Yarnold PR, Corren J, & Saxon A (2000). Review of alleged reaction to monosodium glutamate and outcome of a multicenter double-blind placebo-controlled study. The Journal of nutrition, 130 (4S Suppl) PMID: 10736382
 L. A. Smolin and M. B. Grosvenor, Nutrition Science & Applications. USA: John Wiley & Sons Inc., 2008.