A condition known as Chinese restaurant syndrome (CRS) appeared in the USA in 1968 and its first victim was a Dr Robert Ho Man Kwok who described its symptoms in a leading medical journal, The New England Journal of Medicine. He said it had afflicted him soon after he’d eaten a meal in a Chinese restaurant when he became aware of his mouth had become numb, he felt a tingling sensation in his neck, and he had a headache, all of which lasted about 24 hours. The newspapers seized upon this report and, of course, sensationalised it.
Soon CRS was afflicting many other people, and the agent responsible was said to be mono sodium glutamate (MSG) which was a cooking agent widely used in oriental dishes. This is a flavour-enhancer rather like salt, except that it enhances the umami or savoury flavour of dishes to which it is added. Soy sauce relies on MSG. Today the media scare rumbles on and you can still see labels on some supermarket products that assure the buyer that it contains no MSG.
In fact, while there might be a condition with the symptoms of CRS and caused by the food we eat, it is certainly not due to MSG, as later tests proved. People who said they were affected by CRS were given MSG without their knowledge and suffered no ill effects, while others who said they were allergic to it were given food which they were told contained MSG, but which in fact had not been added, and they then suffered the symptoms to CRS.
In the book ‘Was it something you ate?’ which I wrote with a medical doctor, Peter Fell, we devoted a whole chapter to MSG. Of course you can eat a meal to which had been added too much of this, and then suffer an upset stomach and headache while your body deals with it. In the same way as your body reacts to an excess of other natural chemicals, like alcohol, caffeine, etc.
It is not possible to be allergic to MSG because it is a natural component of a living cell and is a molecule which the human body itself produces. MSG occurs naturally in many foods and is especially high in cheese, peas and tomatoes. It has the food code number E621 which indicates it is regarded as safe to use in EU countries.
MSG has been a part of oriental cooking for centuries, and is generally added in the form of soy sauce. It is possible to eat a meal with a high MSG content, and you might well encounter such a meal in a Chinese restaurant if you were to eat wonton soup, prawns, duck, mushrooms, and soy sauce. If you finish such as meal with something like camembert or brie cheese you might well exceed the 3 grams of MSG that the body can cope with at any one time. Then you might feel uncomfortable for a while afterwards as the body deals with the excess MSG.