Monosodium Glutamate - Safety

Safety

See also: Safety of glutamic acid as a flavor enhancer

MSG has been used for more than 100 years to season food. During this period, extensive studies were conducted to elucidate the role, benefits and safety of MSG. At this point, international and national bodies for the safety of food additives consider MSG safe for human consumption as a flavor enhancer. The "MSG symptom complex" was originally termed as the "Chinese Restaurant Syndrome" when Robert Ho Man Kwok anecdotally reported the symptoms he felt after an American-Chinese meal. Kwok suggested multiple reasons behind the symptoms, including alcohol from cooking with wine, the sodium content, or the MSG seasoning. But MSG became the focus and the symptoms have been associated with MSG ever since. The effect of wine or salt content was never studied. With the years, the list of non-specific symptoms has grown on anecdotal grounds. In normal conditions, humans have the ability to metabolize glutamate that has a very low acute toxicity. The oral lethal dose to 50% of subjects (LD50) is between 15 to 18 g/kg body weight in rats and mice respectively, five times greater than the LD50 of salt (3 g/kg in rats). Therefore, the intake of MSG as a food additive and the natural level of glutamic acid in foods do not represent a toxicological concern in humans.

A report from the Federation of American Societies for Experimental Biology (FASEB) compiled in 1995 on behalf of the United States Food and Drug Administration (FDA) concluded that MSG is safe when "eaten at customary levels" and although there seems to be a subgroup of apparently healthy individuals that respond with the MSG symptom complex when exposed to 3 g of MSG in the absence of food, causality by MSG has not been established because the list of MSG Symptom complex was based on testimonial reports. This report also indicates that there is no data to support the role of glutamate in chronic and debilitating illnesses. A controlled double-blind multicenter clinical trial failed to demonstrate the relationship between MSG symptom complex and the consumption of MSG in individuals that believed to react adversely against MSG. No statistical association has been demonstrated, there were few responses and they were inconsistent. Symptoms were not observed when MSG was given with food.

Adequately controlling for experimental bias includes a double-blind placebo-controlled experimental design (DBPC) and the application in capsules because of the strong and unique after-taste of glutamates. In a study performed by Tarasoff and Kelly (1993) 71 fasting participants were given 5 g of MSG and then administered a standard breakfast. There was only one reaction, and it was to the placebo in a self-identified MSG-sensitive individual. In a different study done by Geha et al. (2000), they tested the reaction of 130 subjects that reported sensitivity to MSG. Multiple DBPC trials were performed and only subjects with at least two symptoms proceeded. Only two people out of the whole study responded in all four challenges. Because of this low prevalence, the researchers concluded that the response to MSG was not reproducible.

Additional studies that have looked into whether MSG causes obesity have given mixed results. There have been several studies investigating an anecdotal link between MSG and asthma; current evidence does not support any causal association.

Since glutamates are important neurotransmitters in the human brain, playing a key element in learning and memory, there is ongoing study by neurologists about possible side-effects of MSG in food but no conclusive studies drawing any connections.