If you visit the best noodle houses in Asia, they will happily tell you their secret: The amino acid glutamate, boiled from dried seaweed or fermented soy, or gotten from a can, where it has been stabilized with salt and given the name monosodium glutamate (MSG). 

MSG is safe but some epidemiological and animal model studies have linked it to obesity and disorders associated with metabolic syndrome, including progressive liver disease. Other studies have disputed that.

Metabolic syndrome has become a common health problem throughout the world, and a major factor in cardiovascular morbidity and mortality. In parallel, the prevalence of its liver phenotype nonalcoholic fatty liver disease (NAFLD) is also increasing dramatically. Various advocacy groups have attributed this to everything from chemical additives to marketing.

A new study claims MSG is a critical factor in the initiation of obesity and shows that a restrictive diet cannot counteract this effect but can slow the progression of related liver disease. This is in defiance of medical reality n Asia, where not everyone has headaches or obesity, like they should if MSG is as bad as claims say, but Makoto Fujimoto and a team of international researchers monitored the weight gain and development of nonalcoholic fatty liver disease and its progression to nonalcoholic steatohepatitis in MSG-treated mice fed either a calorie-restricted or regular diet.  

Outline of the experimental protocol (A), amount of food consumed (B), and body weight changes (C) in the three groups. Thirty-six newborn mice were administered monosodium glutamate (MSG) and, following a 12-week unrestricted diet, were randomly allocated to receive an unrestricted (UNRES) or restricted (RES) dietary regimen. Eighteen mice were not administered MSG and received a restricted diet serving as a control group. Nine mice per group were sacrificed at 6 and 12 months. Credit: doi:10.1089/jmf.2012.0029

"Although MSG has been deemed a safe food additive, its dosage, interaction with other drugs, effects on vulnerable populations, and effects on chronic inflammatory diseases and neurological diseases are unknown," says Co-Editor-in-Chief Sampath Parthasarathy, MBA, PhD, Florida Hospital Chair in Cardiovascular Sciences, University of Central Florida, Orlando, in an editorial.  

Fujimoto Makoto, Tsuneyama Koichi, Nakanishi Yuko, Salunga Thucydides L., Nomoto Kazuhiro, Sasaki Yoshiyuki, Iizuka Seiichi, Nagata Mitsunobu, Suzuki Wataru, Shimada Tsutomu, Aburada Masaki, Shimada Yutaka, Gershwin M. Eric, and Selmi Carlo, 'A Dietary Restriction Influences the Progression But Not the Initiation of MSG-Induced Nonalcoholic Steatohepatitis',  Journal of Medicinal Food. March 2014, 17(3): 374-383. doi:10.1089/jmf.2012.0029.