THE MONOSODIUM GLUTAMATE SYMPTOM COMPLEX - ASSESSMENT IN A DOUBLE-BLIND, PLACEBO-CONTROLLED, RANDOMIZED STUDY

Background: Considerable debate swirls about the validity of symptoms described by many people after ingestion of monosodium glutamate (MSG) , and the question has remained unresolved largely because of a paucit y of well-designed challenge studies. Methods: We conducted oral chall enge studies in self-identified MSG-sensitive subjects to determine wh ether they had a statistically significant difference in the incidence of their specific symptoms after ingestion of MSG compared with place bo. First, 5 gm MSG or placebo was administered in random sequence in a double-blind fashion. Subjects who reacted only to a single test age nt then underwent rechallenge in random sequence in a double-blind fas hion with placebo and 1.25, 2.5, and 5 gm MSG. A positive response to challenge was defined as the reproduction of greater than or equal to 2 of the specific symptoms in a subject ascertained on prechallenge in terview. Results: Sixty-one subjects entered the study. On initial cha llenge, 18 (29.5%) responded to neither MSG nor placebo, 6 (9.8%) to b oth, 15 (24.6%) to placebo, and 22 (36.1%) to MSG (p = 0.324). Total a nd average severity of symptoms after ingestion of MSG (374 and 80) we re greater than respective values after placebo ingestion (232 and 56; p = 0.026 and 0.018, respectively). Rechallenge revealed an apparent threshold dose for reactivity of 2.5 gm MSG. Headache (p < 0.023), mus cle tightness (p < 0.004), numbness/tingling (p < 0.007), general weak ness (p < 0.040), and Bushing (p < 0.016) occurred more frequently aft er MSG than placebo ingestion. Conclusions: Oral challenge with MSG re produced symptoms in alleged sensitive persons. The mechanism of the r eaction remains unknown, but symptom characteristics do not support an IgE-mediated mechanism. According to Food and Drug Administration rec ommendations, the symptoms, originally called the Chinese restaurant s yndrome, are better referred to as the MSG symptom complex.