It has been more than 50 years since the “Chinese Restaurant Syndrome Puzzles Doctors” article was published by the New York Times. The article was a response to a ‘Letter to the Editor’ that appeared in the New England Journal of Medicine (NEJM) several weeks earlier, published under the title “Chinese Restaurant Syndrome”.
The letter, which is not a medical paper but a single anecdote, postulates that symptoms such as weakness, nausea, drowsiness, chest pain, numbness, and heart palpitations are perhaps caused by Chinese restaurants and their use monosodium glutamate (MSG) in their cooking. Over the following weeks, the journal published more anecdotal letters from people recounting similar unpleasant symptoms. As the media coverage increased, more attention was given to MSG, despite the lack of scientific evidence, demonising Chinese food in the process. It was later revealed that the letter was, in fact, a prank.
Adding to the controversy is a study, frequently cited by people who believe they have experienced the Chinese Restaurant Syndrome, published in Nature in 1970 by Dr. J.W. Olney. In the study, highly concentrated doses of MSG are injected into the brains of young mice, leading to higher rates of obesity in adulthood. The mice also suffered tissue death. However, the study’s validity has been repeatedly refuted due to core issues in its design – including that the quantity and mode of administration are inconsistent with the way people consume MSG. Many of the early research studies on MSG are plagued with problems that undermine their validity, such as a lack of control groups, small sample size, reliance on animal models, and other significant methodological flaws.
What is Monosodium glutamate?
Monosodium glutamate, commonly referred to as MSG, is a flavor enhancer and food additive. It is naturally found in many foods such as tomatoes, soy sauce, carrots, cheese, and mushrooms, signaling the fifth taste, umami, after sweet, salty, bitter, and sour. Umami in Japanese means “savouriness”, first discovered by a Japanese chemist, Kikunae Ikeda, in 1908 when he extracted MSG from seaweed broth and filed a patent to commercially produce MSG. Currently, MSG is produced by the process of fermentation of different products such as molasses, sugarcane, beans, and others.
MSG is the salt of glutamic acid. Salt is sodium chloride, so glutamic acid essentially replaces the chloride anion in salt. That is what makes MSG what it is: monosodium glutamate. Glutamate in MSG is chemically the same as the amino acid glutamate found in food proteins and is metabolised in our body in the same way.
The term “Chinese Restaurant Syndrome” is still listed in the Merriam-Webster dictionary with an addendum explaining that the term is offensive and has been replaced in medical literature by MSG Symptom Complex. The Food and Drug Administration considers MSG to be safe, explicitly stating that:
although many people identify themselves as sensitive to MSG, in studies with such individuals given MSG or a placebo, scientists have not been able to consistently trigger reactions.
Countless other studies over the years have concluded that MSG is, in fact, safe.
MSG is one of the most studied food ingredients and decades of research have failed to demonstrate that it causes any adverse reactions. A 2014 research study to evaluate the physiological, metabolic, behavioral action, and safety of MSG explained that dietary MSG does not reach the brain because it cannot cross the blood-brain barrier. MSG does not cross biological membranes and does not pass from the gut into the blood, or from maternal to fetal circulation. A 2016 systemic review of human studies that explores the incidence of headache after ingesting MSG, with or without food, concludes that there is a lack of evidence that supports a correlation between MSG ingestion and headache, noting that the studies reviewed involved the administration of high doses of MSG at high concentrations and that these studies are not properly blinded. A 2020 review published in the Comprehensive Reviews in Food Science and Food Safety journal surveys the available literature on the alleged adverse effects of MSG. The authors conclude that
many of the reported negative health effects of MSG have little relevance for chronic human exposure and are poorly informative as they are based on excessive dosing that does not meet with levels normally consumed in food products.
More than 50 years later, we are still debunking that letter to the editor by research studies. One reason might be the Illusory Truth Effect, the tendency to believe in false information after repeated exposure. Customers are pacified with a “No MSG added” label on products, despite the large body of evidence from double-blind studies that have failed to support the Chinese Restaurant Syndrome.
The so-called Chinese Restaurant Syndrome is the product of the power of belief and the power of the popular press. The media has a profound influence on the actions and beliefs of the average consumer. Despite the large body of research devoted to investigating the safety of MSG and separating myth from reality, the controversy still thrives and the body of anecdotal evidence targeting MSG continues to grow. Although it is plausible that certain individuals might experience hypersensitivity to MSG, there is no evidence to substantiate such claims.
