The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny...' --Isaac Asimov

MSG: Miry Scientific Gabble

September 10th, 2008 by eric

I received a question today about monosodium glutamate (MSG), in particular the concentration of MSG in yeast and yeast extracts, which are often used as flavorings (Nutritional Yeast) and spreads (e.g. Vegemite and Marmite). As usual, I headed to the web to find the answer, and as usual in these kinds of matters, what I found was a miry mix of science, pseudoscience, bias, and bollocks. (What I didn’t find was the answer to that question…) In particular, two competing sites seem to host a lot of the ‘information’ present on the web about MSG. One group is an industry group called the International Food Information Council, which hosts a ‘review’ of the literature, and find, surprisingly enough, that there are no harmful effects of consuming MSG. In that document they highlight a review of a study by Geha et al., and assure us that “any observed reactions were mild, transient, and not life threatening.” The document doesn’t mention that there were statistically significant increases in reactions to free glutamate in almost 40% of the subjects, a self-selected group of people who thought they had previously had a reaction to MSG.

TABLE II. Protocol A (n = 130): Frequency of symptoms reported to challenge with 5 g of MSG versus placebo
$$\begin{tabular}{lrrrc} \hline\hline Symptom&placebo&5g of MSG&relative risk&P < .005\\ \hline General weakness&0.14&0.30&2.17&*\\ Muscle tightness&0.18&0.34&1.83&*\\ Muscle twitching&0.06&0.13&2.13&\\ Flushing&0.08&0.25&3.30&*\\ Sweating&0.04&0.07&1.80&\\ Burning sensation&0.05&0.14&3.00&*\\ Headache/migraine&0.28&0.54&1.89&*\\ Chest pain&0.02&0.06&2.67&\\ Palpitations&0.04&0.10&2.60&\\ Numbness/tingling&0.20&0.28&1.38&\\ At least 2 symptoms&0.27&0.53&1.97&*\\ \hline\hline \end{tabular}$$ You'll notice that half of the reactions were reported significantly more after exposure to MSG than to placebo. They also mention that a number of other reactions were reported in the presence of MSG and not placebo, which aren't listed here. Also note that the low level of significance they chose to determine which reactions were statistically more common: alpha = 0.005. Perhaps this is common in medical literature, I don't know, but a much more common level is ten times higher, alpha = 0.05. Their choice of a much lower level means that these 5 reactions were highly significantly more frequent after MSG than not. The authors acknowledge this but then discount these results later because they were not ‘reproducible’ and because of something they term ‘demand bias’. I don’t know what this term means, but it doesn’t appear commonly in the literature. In a search of Google Scholar, many of the papers that came up bearing this term were related to glutamate studies. Oh, did I forget to mention that this study, and most of the others, were funded by various branches of the glutamate industry? oops… This particular papers bears the note “Supported by a grant from the International Glutamate Technical Committee”, which bears some kind of relation to the “The Glutamate Association“.

An explanation of these groups is found on the other website I mentioned before, Truth in Labeling. This consumer advocate site contains, predictably, a lot of anecdotes and ad hominem attacks against the industry (advocates of which are deprecatingly termed ‘Glutes’). It also contains some analyses and fact-checking on the studies and news releases put out by the MSG industry. On the whole, I’m with them. Outspent and out-shouted, they’re doing what they can to understand the true ramifications of this pervasive substance in our food supply, without much help from independent researchers.

Nevertheless, if industry goes too far in denying reactions to MSG, consumer advocates probably go too far in pursuing claims of reactions to MSG. Of course, replace ‘MSG’ in the last sentence with innumerable other chemicals compounds and it will still be just as true. Both the under- and over-interpretation of data can lead to bias and general confusion over the true meaning of the findings. I suspect that MSG really is safe in modest quantities for most people, but that some people can have adverse reactions that can range from discomfiture, to discomfort, to true danger. Unfortunately, I’m doubtful that those on either side of arguments like this are willing to make the kind of intellectual concessions necessary to find the grain of truth amidst the hyperbolic grit.

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