Although monosodium glutamate (MSG) is categorized as a causative compound of headache in the International Classification of Headache Disorders 3rd edition, there is no literature in which causal relationship between MSG and headache was adequately examined. Researchers carried out methodical evaluation of human studies which include the occurrence of headache after an oral administration of MSG.
An analysis was made by separating the human research studies with MSG administration with or without food, since of the significant difference of kinetics of glutamate in between those conditions and there are some documents which report the difference of the symptom of symptoms after MSG intake with or without food.
Of 5 documents including 6 research studies with food, none showed a significant difference in the occurrence of headache other than for the female group in one study. Of five papers consisting of seven studies without food, four studies showed a substantial difference. A number of the research studies involved administration of MSG in solution at high concentrations.
Because the distinct MSG is easily recognized at such concentrations, these research studies were thought not to be appropriately blinded. Because of the absence of appropriate blinding, and the disparity of the findings, they conclude that further studies are needed to evaluate whether a causal relationship exists in between MSG consumption and headache.
Monosodium glutamate is used worldwide as a taste enhancer. So called Chinese dining establishment Syndrome (CRS) was first reported by Kwok in 1968. He reported that after consumption of Chinese meals, some transient subjective symptoms happened such as numbness, basic weakness, palpitation, etc. Although numerous human research studies were conducted afterwards to identify if a causal relationship happens between MSG and this symptom complex, the results were inconsistent. Headache was reported to be one of this symptom complex.
The safety of glutamic acid and its salts as taste enhancers was assessed by the Joint FAO/WHO Expert Committee on Food Additives and it designated an “acceptable everyday intake (ADI) not defined” based upon the conclusion that the overall consumption of glutamate emerging from their use at levels necessary to achieve the desired technological result and from their acceptable background in food do not represent a danger to health.
In this evaluation, they report the results of a methodical evaluation of offered human research studies of MSG, focusing on the causal relationship between MSG intake and headache by different analysis of the research studies with MSG administration with or without food. They likewise go over the clinical validation of ICHD-III beta on MSG, based upon our review of the research studies pointed out.
Because the majority of the human research studies that include information on the headache incidence concentrate on symptom complex and do not particularly concentrate on headache, search condition was enhanced to get as lots of human study data with MSG administration as possible.
The literature search was conducted on Medline and FSTA. Initially, they looked for titles that includes any of the following terms: “monosodium glutamate”, “MSG”, “monosodium L-glutamate”, “salt glutamate”, and “salt L-glutamate”. In case of Medline, the search was narrowed down by specifying short article type as “clinical trial”.
The above search result was additional narrowed down by the list below conditions; the paper is composed in English, the paper is a human research study with the administration of MSG using healthy adults, the occurrence of headache is revealed, and a statistical analysis was performed on the incidence of headache, or the paper consists of adequate information with which to carry out statistical analysis.
Human research studies with MSG administration with food
Concerning the research studies with the MSG administration with food, five papers which include 6 research studies were found.
On the study reported by Praworphardjono and at the first stage of Tarasoff’s research study, 1.5, 3.0 g MSG or placebo in pills was administered in fasted conditions, followed by the consumption of a standardized breakfast. At the second stage of Tafasoff”s research study, the topics consumed a specifically created soda that included 3.15 g MSG or placebo, and after that consumed the standardized breakfast.
Although at this 2nd stage, some topics may be able to identify placebo and MSG drink, they examined just the information from 61 subjects, who reported no after-taste, out of 71 subjects. In all research studies by Praworphardjono and Tarasoff, no difference of incidence of headache in between placebo and MSG administration was found and the authors concluded that rigorous and practical clinical proof connecting CRS to MSG could not be found.
Tanphaichitr investigated the incidence of unpleasant symptoms after intake of a breakfast consisting of included MSG or no included MSG. In the first experiment, using 10 subjects, a menu that masked the taste of MSG was identified. 4 menus without MSG and one menu with 3 g MSG were served to 50 subjects as a breakfast on day 1 — 5 one-by-one. Nobody served with the menu containing MSG had a headache and the author concluded that the addition of MSG did not cause substantial difference in undesirable symptoms of CRS from those on menu without MSG.
Therefore, those three research studies above can be thought properly blinded, however the following two research studies reported by Zanda and Morselli might not ensure the enough blind stability. In both research studies, 3 g MSG in 150 ml beef broth was administered followed by other dishes. No substantial difference in the incidence of CRS symptoms was discovered in both studies, with the exception of headache incident amongst females in Zanda’s research study: an incidence in 6 topics was observed on the MSG day, however only 1 on the placebo day.
Scientifically meaningful distinctions in objective indices, such as arterial blood pressure and pulse rate, were not observed. In overall 73 subjects (38 males, 35 women) joined this research study. Keep in mind that the number of migrainers is higher in females than in males, and undesirable taste and undesirable sensation caused by high dosage of MSG may end up being a stimulant to activate headache on migrainers particularly when they are fasted. Placebo result by appreciable taste also should not be neglected.
In the research study by Morselli, they concluded that no difference in all CRS symptoms consisting of headache between the topics provided MSG and control broth.