In 1968 Dr. Robert Ho Man Kwok, an American physician who had been born in China, experienced a severe reaction after eating food in a Chinese restaurant. Noting that similar symptoms were unknown in China, he coined the term Chinese restaurant syndrome to describe toxicity of MSG. A controversy over the validity of the syndrome ensued, but in 1995 a panel of experts convened by the FDA agreed that MSG could cause short-term effects when consumed in a dose of at least 3 grams, roughly equivalent to the amount of MSG in six servings of commercially prepared Chinese food.
MSG may aggravate other conditions. in 1981, a letter to the new England Journal of Medicine described two people with asthma who appeared to suffer MSG sensitivity. in these patients, consuming about 2.5 grams of MSG (five servings of Chinese food) results in severe wheezing and bronchospasm about 12 hours later.
A clinical trial of the effects of MSG in 1987 found that other asthmatics were also sensitive, but they were only a small fraction of the total asthmatics tested, 2 out of 30. another clinical trial in 1999 tested the idea that MSG might be more of a problem for aspirin-sensitive asthmatics. It was not. Only one person in the trial showed any reaction to MSG, and although a measure of the depth of her breathing called FEV was decreased by 20 percent, she did not suffer wheezing, coughing, or other noticeable symptoms. Even she did not react to MSG the second and third time she was tested.
The medical literature also records one case in which MSG ingestion seems to have caused hives. A letter to the British medical journal Lancet described a 50-year-old man with hives on the face and hands after drinking a soup made with an MSG-flavored soup base. all he had to do to avoid further outbreaks of hives was to avoid the soup. A follow-up study found that some children could develop hives after consuming only 50 mg of MSG, about 10 percent of the MSG in a single serving of commercially prepared Chinese food. they only developed hives, however, if they were taken off all their usual allergy medications before the test.
Eventually, MSG researchers agreed to a list of symptoms:
- Sensitivity to light
- Tightness in the chest
- Visual disturbances
Symptoms occur 2-3 hours after eating food prepared with MSG.
The most reliable scientific evidence of a link between MSG and exacerbation of disease has been found in studies of headaches. in a double-blind test conducted in 1969, two out of four migraine patients developed headaches after exposure to soy sauce containing 1.5 to 2 g of added MSG. they did not develop headaches when given soy sauce that did not contain MSG. Since all soy sauce contains natural MSG, the researchers did not know for sure whether the migraine trigger was MSG or something else in the soy sauce.
Since the clinical evidence for a link between MSG and asthma, hives, headache, nausea, and/or vomiting is equivocal, no one should embark on a long-term regimen of avoiding MSG without first making sure MSG is the source of the problem. the way to do this is to avoid foods with MSG for at least two weeks, and then to try a regular portion of food with MSG added. if there is a bad reaction, then make the effort to avoid MSG over the long term. if you don’t have a bad reaction to MSG, however, take another two-week vacation from MSG and then see if you can tolerate a larger serving. if you don’t have a bad reaction either time, then MSG restriction is probably an unnecessary dietary burden for you.