Table 2.

Reviews regarding the impact of MSG on human health

Objective	Conclusions	Observations	Reference
Evidence-based safety review	MSG is safe for all life-cycle stages. No alterations of nervous system function or of blood concentrations of pituitary hormones were found.	The human body does not discriminate between naturally occurring glutamate in foods and added glutamate. Added MSG is much lower than daily dietary glutamate intake from natural sources. Thus, it is hard to attribute causal role in major central and endocrine pathologies only to MSG used as a flavor enhancer.	(Henry-Unaeze, 2017)
Systematic review assessing the incidence of headache after an oral administration of MSG. Studies were analyzed taking into consideration MSG administration in relation to meals, due to the significant differences in kinetics when taken with or without food.	Five papers of MSG administered with food were analyzed and none showed a significant difference in the incidence of headache except for the female group in one study (dose: 3 g in 150 mL beef bouillon). Of seven studies without food, four studies showed a significant increase in the frequency of headaches.	MSG was administered, being dissolved in beverages or soup at relatively high concentrations. Authors emphasize that most of the studies involved administration of MSG in high concentrations (>2%), and it could easily be identified, due to its unpleasant taste at concentrations over 1.3%, and, as such, these studies were not properly blinded.	(Obayashi & Nagamura, 2016)
Assessment of the effects of MSG consumption on human health	No effects of MSG administration on postprandial glycaemia and insulinemia were found. No correlation between MSG consumption and obesity was found.	Results regarding the association of MSG intake with CRS and asthma were contradictory. Clinical trials with better design are needed for a conclusion.	(Husarova & Ostatnikova, 2013)
Assessment of the possible role of MSG in the so-called ‘Chinese restaurant syndrome’ and in eliciting asthmatic bronchospasm, urticaria, angioedema, and rhinitis	Large doses of MSG (>3 g) ingested on an empty stomach without concomitant food ingestion may elicit some of the symptoms associated to CRS. It is unlikely that MSG consumption plays a role in the provocation of asthma. Dietary ingestion of MSG may be a rare cause for urticaria (accounting for under 3% of cases) and angioedema.	There is no evidence that dietary MSG of a typical western diet induces symptoms of the CRS. There are not enough data to associate MSG consumption with rhinitis. The overall quality of the evidence supporting a relationship between MSG consumption and for urticaria and angioedema is low.	(Williams & Woessner, 2009)
Assessment of correlation between MSG consumption and Chinese restaurant syndrome	Doses of 5 g of MSG given without food may determine symptoms (general weakness, muscle tightness, flushing, sweating, headache, numbness or tingling) in individuals who are self-proclaimed “MSG sensitive”.	The frequency of the responses was low and the responses were inconsistent and not reproducible. The results were not observed when MSG was given with food.	(Geha et al., 2000b)
Literature review and original study of link between MSG consumption and Chinese restaurant syndrome	No evidence linking the CRS associated symptoms to MSG consumption was found.	MSG was administered in doses of 1.5, 3.0 and 3.15 g/person in capsules and specially formulated drinks, before breakfast.	(Tarasoff & Kelly, 1993)