In 1968, a letter to the editor in the New England Journal of Medicine noted that when the writer and his friends would go to Chinese restaurants, they would often have a certain set of unpleasant symptoms afterward: numbness in the back and arms, palpitations, a general feeling of weakness. This wasn’t a scientific paper or a medical paper. It was a letter to the editor—which anybody can write—proposing a question. The writer was a doctor, but not a specialist in anything that would have to do with MSG chemistry. He wondered whether there was a connection between what he and his friends ate at the Chinese restaurant and their symptoms.
He also noted that Chinese restaurants often used MSG as a seasoning, and that that was one thing that distinguished Chinese restaurants from other restaurants—so consuming large quantities of MSG might have had some connection to that set of symptoms. The journal gave his letter the title “Chinese Restaurant Syndrome,” and then printed a number of follow-up letters in later issues under the same title. That’s part of the reason that these anecdotal letters to the editor got more attention than they deserved. The media picked up on the catchy title, neglected the fact that the letters were mostly speculation, and encouraged the belief that MSG was known to cause these symptoms in people who go to Chinese restaurants.
But the important thing to know is that, hundreds and hundreds of studies later, there is no evidence that MSG causes the symptoms of Chinese Restaurant Syndrome. This was an unfortunate episode that should teach us a lot about carefully reading proposals of cause and effect between something we eat and some effect that it might have. Eating is a very complicated subject, diet is a very complicated subject, and foods are very, very complicated materials. It’s usually very difficult to draw a straight line from one ingredient to a particular symptom or a particular problem. In the case of MSG, the record is about as clear as it can be: there is no connection between consuming MSG in any form and the symptoms that are often called Chinese Restaurant Syndrome.