Adverse Health Effects of MSG: Will Chinese Take-out Take You Out?
Oral ingestion of monosodium L-glutamate, particularly when used as a seasoning in Chinese restaurant meals, has been implicated in a growing number of adverse reactions. These range from the classic Chinese Restaurant Syndrome triad of symptoms (facial pressure, chest pain, and a burning sensation) to documented cases of MSG-induced asthma. A number of double-blind, placebo-controlled studies have confirmed a relationship between MSG dose and CRS symptom duration and intensity, with a challenge threshold around 2.5 gm. Studies have also confirmed MSG-provoked asthma attacks in susceptible individuals, which exhibit a reproducible time delay. While the existing data are not overwhelming, they do suggest the existence of certain subgroups within the general population that are predisposed to MSG-induced symptoms, both the CRS and asthma. Current mechanisms under consideration involve the effects of elevated serum glutamate level mediated through central and/or peripheral glutamate receptors. Much research remains to be done.