Chinese Restaurant Syndrome

Dinig out at a Chinese restaurant may not be as uneventful as you think

By Sheila R. Alcantara, MD

Nothing comes close to ubiquity as Chinese food. Even a thousand miles off its native origin, from Canton to Hong Kong to Manila to London to New York, people all over the world have had at some point in their lives an experience of MSG heaven… that feeling of gustatory mania that is so characteristically Chinese.

    But other than just satisfying one's hunger and craving, Chinese food, for some time now, has been implicated in producing such varied symptoms as numbness, palpitations, chest pain, even headache. This constellation of subjective complaints noted after intake of dimsum, ma-chang, hofan and the like has actually been baffling scientists for more than three decades past, and it now appears that for a very small subset of people, at least, the experience may be more than harmless.

CRS Exposed

    It was in 1968 that the first observation on the triad of "numbness at the back of the neck, gradually radiating to both arms and back, general weakness, and palpitations" was described by Dr. Kwok in the New England Journal of Medicine. These unusual reactions were experienced 15 to 30 minutes after eating a Chinese meal and would spontaneously resolve after about two hours. The author likened these symptoms to acetylsalicylic acid or aspirin hypersensitivity, although he also suggested other possible instigators, such as salt, alcohol, and MSG or monosodium glutamate used as food additives. This complex of symptoms was then called the Chinese Restaurant Syndrome or CRS.

    Since then, numerous accounts, mostly anecdotal, have been published based on the original observation. Various other manifestations were also noted, including flushing, tingling, sweating, nausea and vomiting, abdominal pain, tearing, syncope, dizziness, and migraine. Even conditions such as asthma, urticaria, atopic dermatitis, orofacial granulomatosis, neuro-psychiatric diosorders, and arrhythmias were reportedly associated with intake of Chinese cuisine. Many, however, dispute the existence of such adverse reactions.

Usual Suspects

    Numerous mechanisms have been proposed to explain the range of symptoms produced in CRS. Many theories have been put forward, but none have been conclusively proved.

    For example, high salt content has been suggested, as researchers noted elevated plasma sodium levels after a Chinese meal. Moreover, when the histamine content of ingredients used in Chinese cuisine was measured, some groups found the levels close to the toxic threshold for histamine in foods as established by the Food and Drug Administration, leading the authors to hypothesize that histamine may be what's causing CRS.

    On the other hand, typical reactions to MSG were noted to be similar to those of vitamin B6 deficiency. In fact, the proponents suggested that symptoms did not recur after vitamin B6 supplementation, and proposed that CRS is actually a manifestation of vitamin B6 deficiency. Some researchers, meanwhile, view the symptoms to be similar to acetylcholine administration. Others insist that it is an indication of esophageal irritation.

    Finally, since the original hypothesis by Kwok, MSG has become the most commonly implicated culprit of all these varied symptoms. As a favorite flavor enhancer in Chinese food, it has undergone careful scrutiny from researchers all over, with studies ranging from mere uncontrolled open challenges to more sophisticated double-blind placebo controlled trials. While the definitive causation of CRS is still largely unknown, sensitivity to MSG has become a major concern.

The Scoop on MSG

    Monosodium glutamate is a sodium salt of the amino acid glutamic acid. Its use in cooking dates back to Oriental antiquity, when seaweeds called sea tangle (Laminaria japonica) were used to make starch. The Japanese eventually produced glutamate from these slimy plant forms, and after some time, it was also derived from corn and wheat gluten in other countries. Today, MSG is produced by fermentation of sugar beet molasses and is commonly used as a flavor enhancer in sauces, gravies, soups, broth, as well as in a wide variety of dishes and preserved foods. It also occurs in hydrolyzed and textured vegetable protein, gelatin, yeast extracts, calcium and sodium caseinate, vegetable broth, whey, smoke flavoring, and malt extracts.

    The average person in an industrialized country consumes about 300 to 1000 mg of MSG per day. But as much as five grams of MSG may be ingested in a highly seasoned restaurant meal. Although estimates of the prevalence of sensitivity to MSG are unreliable, it is thought to be less than one percent of the population.

The MSG-CRS Link

    A lot of research has implicated monosodium glutamate as the agent responsible for CRS; however, results have been conflicting. In some double-blind, placebo controlled (DBPC) studies, it was shown that MSG challenge of individuals who believe themselves to be sensitive did not elicit symptoms typical of CRS, and in fact, produced reactions similar to other foods. Moreover, MSG mixed with food rather than administered in pure form has generally shown a lack of symptoms altogether.

    Meanwhile, other studies show that high doses of MSG may be associated with adverse reactions. In a DBPC study published in the Journal of Allergy and Clinical Immunology in 1997, Yang and colleagues showed that oral challenge with MSG reproduced symptoms in self-identified MSG-sensitive persons. Increasing severity and frequency of symptoms were also noted with mounting doses of MSG. Their data also indicate that the mechanism is probably not IgE-mediated or allergic in nature. Geha et al. in 1998 concluded that large doses of MSG given without food may elicit more symptoms than placebo in individuals who believe that they react adversely to MSG. But neither persistent nor serious effects were consistently demonstrated and responses were not observed when MSG was taken with food.

    Finally, the FDA has classified MSG as "generally recognized as safe" (GRAS). In order to shed light on these accounts of adverse reactions to MSG, it sponsored extensive reviews on its safety by the Federation of American Societies for Experimental Biology (FASEB). In 1995, FASEB came out with a report reaffirming the GRAS status of MSG. It also used the term "MSG symptom complex," instead of Chinese Restaurant Syndrome, to refer to the acute, temporary, self-limiting complex, composed of the following:

    o a burning sensation of the back of the neck, forearms, and chest

    o facial pressure or tightness

    o chest pain

    o headache

    o nausea

    o upper body tingling and weakness

    o palpitation

    o numbness in the back of the neck, arms, and back

    o bronchospasm (in asthmatics only)

    o drowsiness

    It also concluded that although there was no significantly verifiable scientific evidence to support the occurrence of adverse reactions in persons exposed to high levels of MSG, and there is sufficient documentation to indicate that a subgroup of presumably healthy individuals manifests with symptoms within an hour of exposure to a bolus dose of three grams of MSG taken without food. The FDA confirmed the safety of MSG at levels normally consumed and affirmed that there is no evidence linking MSG to any serious long-term medical problems in the general population.

The MSG Symptom Complex

    Although sensitivity to MSG is not a universally recognized medical condition, and may occur in only a small cluster of people, caution must be exercised by individuals noted to experience adverse reactions after its intake. Typically, doctors recommend avoidance of foods rich in MSG in people with documented sensitivity to MSG. On the other hand, antihistamines may be used in severe reactions, while life-threatening symptoms, though noted to be extremely rare, must be treated accordingly. Fortunately, such reactions are short-lived and generally resolve within two to three hours even without treatment. The prognosis is excellent, and no long-term sequalae have been reported.

MSG or no MSG

    Life without the flavor-enhancing properties of MSG can get pretty bland. While experts agree that more research needs to be undertaken to confirm and understand completely the phenomenon that is the Chinese Restaurant Syndrome (or the MSG symptom complex) MSG continues to color the experience of everyday eating-that joy of life that makes it all worthwhile-whether it's Chinese food or not.