Is MSG harmful, and where did 'Chinese restaurant syndrome' begin?

For most people, MSG is not harmful at the amounts normally eaten. The US Food and Drug Administration, the World Health Organization and the European Food Safety Authority have all concluded that it poses no health risk at typical dietary levels. The idea of a 'Chinese restaurant syndrome' traces to a 1968 letter in the New England Journal of Medicine, followed by early studies that later researchers judged shaky. A small number of people may report mild, short-lived reactions. [1] [2]

In April 1968, Robert Ho Man Kwok, a Maryland physician, wrote to the New England Journal of Medicine about a racing heart, weakness and numbness he felt after eating at restaurants serving Northern Chinese food. He named three possible causes: salt, cooking wine or MSG. A month later the journal printed 10 replies from doctors who described discomfort after Chinese meals. No two listed the same symptoms, and the doctors blamed many different things, including duck sauce, mustard, wonton soup and even the effort of using chopsticks. One neurologist cleared MSG, saying he cooked with it at home without any effect. [3] [1]

The Science History Institute notes that the journal's editors treated the replies with a smirking editorial, but newspapers ran the story seriously. It also places the episode in a 1960s mood of wariness toward chemicals and additives, in which a 'foreign' ingredient made an easy target. National Geographic adds that a 1969 paper in Science gave the MSG theory a scientific veneer despite weak, anecdotal evidence, and that restaurants began posting 'No MSG' signs. [3] [1]

Some accounts call the original letter a hoax. The BBC and The Conversation both use that description. The Science History Institute's account instead presents Kwok as a physician sincerely asking a question, so the sources differ on this point. [4] [2] [3]

The early experiments were weak. One 1969 study had parts with only six and nine participants. Since then, scientists have run many controlled, blinded studies, and the vast majority of the evidence suggests MSG causes no harm. An early randomised trial found no difference in symptoms between people given MSG and those given a placebo, and a review of many studies has confirmed this. In one study of 100 people with asthma, 30 of whom believed they were sensitive to MSG, none reported a reaction when they did not know whether they were consuming it. [3] [2]

Two major safety reviews, a UN expert committee in 1987 and one by the Federation of American Societies for Experimental Biology in 1995, judged MSG safe for the general population. A 2019 literature review concluded that claims linking MSG to a range of ailments were unsubstantiated. [2] [4]

The condition is now called MSG symptom complex. Reported symptoms include flushing, headache, muscle aches, tingling, palpitations, and numbness or burning around the mouth. They are usually mild and pass quickly. The FDA found minor reactions in people who took 3 grams or more of MSG alone without food, while most foods with MSG contain under 0.5 grams. [5]

In 2017 the European Food Safety Authority set a limit based on body weight, aimed at preventing headaches and raised blood pressure: 2.4 grams of added MSG a day for an 80 kg person. Europeans average 0.3 to 1 gram daily, and people in Asia roughly 1.2 to 1.7 grams, so typical intake sits below that limit. [2]