Writing in Clinical & Experimental Allergy, researchers from Scripps Clinic in San Diego report that, despite “anecdotal reports and small uncontrolled studies alleging a variety of MSG-induced reactions […] decades of research have failed to demonstrate a clear and consistent relationship between MSG ingestion and the development of these conditions”.
MSG intensifies and enhances flavour without having a taste of its own, and also has the properties to act as a nutrient, as well as a dietary and salt substitute. The use of the ingredient, popular in many Asian cuisines, looks set to increase its presence in the west.
Indeed, the global market for fermentation products is expected to rise by 4.8 per cent per year, to reach €13.6 billion in 2009. Lysine and monosodium glutamate (MSG) are the largest products in this category.
Japanese firm Ajinomoto dominates the amino acid market, with more than 25 per cent of the market for lysine alone and 30 per cent of the MSG. ADM and BASF also figure in the handful of players that dominate the landscape.
Concerns over the additive first surfaced in the late 1960s following description of the 'monosodium glutamate symptom complex' or 'Chinese restaurant syndrome'. The concerns centred on indications that MSG may worsen asthmatic symptoms.
In order to address this issue, Katharine Woessner and Adam Williams undertook a “critical review of the available literature related to the possible role of MSG in the so-called 'Chinese restaurant syndrome'”.
According to the overall literature, including the 1995 review by FASEB, no direct link between MSG and asthma is found, they said. Furthermore, “the few studies that, at first glance, appear to identify a small number of MSG-sensitive asthmatics have significant design flaws that leave the significance of their findings in question”, said the San Diego-based researchers.
Consideration was also given to a potential increased of other allergic conditions, such as hives (urticaria), swelling of different tissues such as the throat or tongue (angio-oedema), and runny nose (rhinitis). In terms of rhinitis, double-blind, placebo-controlled challenges with 100 mg capsules of the flavour-enhancer were found to produce severe rhinitis in a study with three people, with symptoms lasting for as much as two days. The Scripps researchers said that, while this offers a possible relationship between MSG and rhinitis, further studies are needed before any firm conclusions can be drawn.
“While there is some evidence to suggest that large doses of MSG (greater than three grams) ingested on an empty stomach without concomitant food ingestion may elicit some of the symptoms of the ‘Monosodium glutamate symptom complex’, it would be inappropriate to conclude that MSG consumed as part of a typical western diet would be likely to induce such symptoms,” wrote Woessner and Williams.
“In short, the current evidence does not suggest that MSG is a significant contributor to asthma, urticaria, angio-oedema, or rhinitis,” they concluded.
Source: Clinical & Experimental Allergy May 2009, Volume 39, Issue 5, Pages: 640-646“Monosodium glutamate 'allergy': menace or myth?” Authors: A. N. Williams, K. M. Woessner