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Chemical Concerns Undeserved Reputations

Monosodium Glutamate – An Undeserved Reputation?

Undeserved Reputation - Monosodium Glutamate
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Monosodium glutamate, or MSG for short, has long been the villain of the food supplement world. In the UK, Chinese takeaways proudly display ‘No MSG’ signs beside their counters, and many websites will purport to tell you ‘the truth about MSG’. Numerous studies have been carried out examining the effects of MSG, but with all the conflicting information, it can be hard for consumers to know who to believe.

MSG was first isolated from seaweed in Japan in 1908. It was said to contribute an ‘umami’ flavour when added to dishes; ‘umami’ is derived from the Japanese word for ‘tasty’. By the mid-20th century, MSG was a commonly used supplement in Japanese and Chinese cuisine, and had also spread to numerous other countries, including the USA, where it was routinely used in restaurants and takeaways across the country.

The term ‘Chinese restaurant syndrome’ was coined by a Chinese-American doctor, Robert Ho Man Kwok, who wrote a letter to a scientific journal complaining of experiencing palpitations and numbness after eating in Chinese restaurants. Kwok didn’t identify any particular component of his meal as causing this effect, but, despite the scarcity of evidence, MSG was quickly fingered as the culprit. A study carried out by a Dr John Olney around the same time found that, when MSG was injected into the brains of mice, it could cause brain damage.

Whilst this may seem concerning, an oft-omitted fact when reporting this study is that Olney used huge quantities of MSG in his studies, up to 4 grams per kilogram of body weight all at once, an amount many times higher than humans are likely to consume as part of a balanced diet. To put this into perspective, in industrialised nations it’s estimated we ingest no more than 1 gram over the course of a day, and often much less. In order to match the highest dosage used in Olney’s tests, we’d have to consume 300g of MSG all at once – a quantity many times more than the amount of MSG found in an average Chinese takeaway meal.

Olney also produced results in primates with high doses of MSG, but these haven’t been replicated by other studies attempting to observe the same results. Whilst this doesn’t completely discount Olney’s observations, replicability is a very important part of scientific testing. Without this, we don’t have convincing proof that high amounts of MSG can cause brain damage in primates, nor can we really state anything about human reactions to MSG from these results.

Another study of interest is one carried out in the 1970s, which for six weeks fed 11 subjects up to almost 150 grams of MSG, and noted no ill effects as a consequence. The fact of the matter is, that despite the plethora of symptoms that MSG has been linked to over the years, there is absolutely no scientific evidence for any of them. Numerous studies and reviews have failed to find any correlation between undesirable symptoms and MSG, and its use as a food supplement is still approved by food regulatory bodies. The few trials that have found links have often been criticised for poor trial design – for example, not having any blinding of testing, so subjects knew that they were ingesting MSG, which could obviously colour their feedback.

Chemically, MSG is simply the sodium salt of glutamic acid, which is a naturally occurring amino acid. Glutamate, the deprotonated form of glutamic acid, is found in tomatoes, ham and cheese, and is chemically the same as MSG – both are treated in exactly the same way by the body. If MSG did cause the symptoms commonly attributed to it, then you’d fully expect eating foods high in glutamate to produce exactly the same effect. Oddly, you don’t tend to hear anyone complaining of ‘Chinese restaurant syndrome’ after eating cheese.

Some people may point to anecdotal evidence of their own, that they’ve experienced allergic reactions to MSG in foods. Well-controlled studies have failed to find a link, however; in one study, in which 71 subjects were administered either MSG or a placebo, only one subject reported a reaction. This subject received the placebo in the test. Many other tests have documented cases where subjects who identify as MSG sensitive react to the placebo test, rather than MSG, suggesting there may also by psychological factors at work. It is suggested that a very small number of people may be sensitive to larger amounts of MSG, but the symptoms of this reaction are mild. Those who complain of MSG sensitivity may also be reacting to some other substance in the food, rather than MSG itself. 

Regardless of the scientific evidence, the calls from some quarters to ban MSG from all foods are a little over the top. The possibility of mild reaction in a very small number of people, and only when amounts much higher than those usually present in our diet are ingested, shouldn’t be a cause to ban it as a food additive for the vast majority of consumers for whom it is documented as having no effect. In summary, it’s clear that MSG is somewhat the victim of a character assassination, and we shouldn’t be worrying about the amounts we ingest on a daily basis. However, if you want to read more of the evidence yourself, check out the links supplied in the references section below.

You can also check out the ACS Reactions video on MSG, which can be viewed here.

This post and graphic will appear in a modified form in “Compound Interest: The Curious Chemistry of Food & Drink”, published by Orion in May 2015.

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References & Further Reading

47 replies on “Monosodium Glutamate – An Undeserved Reputation?”

The structures of glutamate/glutamic acid are either unrealistic or just wrong. The structure you have for glutamic acid is the “neutral” structure, which does not exist in any appreciable amount (physiologically the zwitter ion form is most abundant).

The glutamate structure is wrong – the side chain carboxylic acid should be deprotonated (the other one can be deprotonated here, but doesn’t have to be) also at any pH that would deprotonate the acid the amino group would certainly be protonated (NH3+ not NH2).

As far as the glutamic acid structure goes, since the graphic isn’t really focused on glutamic acid, I just went for the general structure. I don’t think that this is a problem in the context of the graphic.

As for the structure of the glutamate ion, I concede that I included the structure shown to show the form of the ion in monosodium glutamate, since that’s the primary compound being discussed. Admittedly, in foodstuffs, the ion you describe is correct; and therefore it may be worth changing with clarification.

Tomatoes, ham and cheese are all migraine triggers. Many of the ‘MSG syndrome’ symptoms are also symptoms of migraine. And, turns out, migraine seems to be under-diagnosed.
I’ll give you that there’s no evidence that MSG is universally toxic, but yes, if I (knowingly or unknowingly) eat something with MSG, I get a migraine. As I will if I eat cheese, too much tomato, or preserved meats, among other foods (especially those strong in umami).
I wonder whether the original ‘Chinese restaurant syndrome’ people had usual diets low in migraine triggers.

This article is pure, unadulterated American Chemical Society BS propaganda.

Just because something is “safe”, doesn’t mean it won’t sicken a large percentage of the population or even kill some of them.

Peanuts are “safe” but can instantly kill a child who is allergic.

A significant percentage of Caucasians are genetically unable to metabolize lactose.

Gluten will tremendously sicken those with Celiac disease and mildly sicken even more who are less sensitive to the stuff.

Large numbers of people are sickened by sodium metabisulfite.

Really, the list of substances like these is very large. And MSG is one of them. Even Mayo Clinic says avoid the stuff if it makes you sick: http://www.mayoclinic.org/healthy-living/nutrition-and-healthy-eating/expert-answers/monosodium-glutamate/faq-20058196

Personally, larger amounts of MSG, any amount of aspartame, or any amount of Stevia will instantly give me a vicious headache.

As it happens, I’m unaffiliated with the American Chemical Society; I’m just a chemistry teacher keen to tackle the common misunderstandings about chemicals, and those about MSG are certainly up there.

The point you make about peanuts and lactose perfectly illustrate my concluding point – that, just because something is considered to have a negative effect on a small number of people, doesn’t mean that it should be immediately banned from use. I’m sure we’d all agree that banning nuts because some people are allergic to them would be ridiculous. I won’t address the other points, as they’re not really overly relevant to a debate about the safety of MSG – we’re not discussing the safety of other chemicals here, but that of MSG, which is independent of the other examples you cite.

You may have noted that the post here didn’t state that MSG never effects anyone negatively; there is some scientific evidence that very high amounts can cause some mild symptoms in a small number of people. That’s exactly what the link you provided concurs with: “Researchers acknowledge, though, that a small percentage of people may have short-term reactions to MSG. Symptoms are usually mild and don’t require treatment.”

It also takes the line adopted in this article, however: “researchers have found no definitive evidence of a link between MSG and these symptoms.” The facts are that a large number of well designed, double blinded studies have failed to find a link. Some of these studies have even deliberately used subjects who identified as MSG sensitive, and yet still failed to show consistent and reproducible reactions to MSG under test conditions – see this review: http://jn.nutrition.org/content/130/4/1058S.short

There is obviously anecdotal evidence of MSG sensitivity, but the reason we require scientific evidence is that it removes all other factors. If MSG can’t be shown in isolation to produce symptoms, then we can’t conclude, scientifically, that it causes any. Aspartame is another which has a bad reputation (bizarrely, far more so in the US than the UK), but again, is something of a victim of a character assassination. What I will say regarding aspartame is that it has been shown to cause problems for those with phenylketonuria, as sufferers are unable to metabolise it; but it’s safe for the majority of the population.

[…] One site uses a pleasant-looking infographic to explain why studies critical of monosodium glutamate are flawed (the MSG was injected rather than ingested, dosage amounts were too high, ingested amounts were without food, etc.). The site also reiterates that “decades of research” have not found a link between monosodium glutamate and reactions. […]

I knew I’d see some armchair chemists before I even looked at the comments. Oh bother, everyone’s an expert because they read half an article for 5 minutes…

[…] Monosodium Glutamate will be a thing you want to remember from this day forward, and you’re asking why and the answer for that why is that it is known as a serious “flavor enhancer” improving the food’s quality of taste. Now I know those out there are going to say right away… […]

Did the MSG trade associations fund this? Lot’s of people react negatively. It’s the big money industry studies I would not trust. Show your funding.

This post, and this site, aren’t funded by anyone – it’s completely independent. I’m a chemistry teacher by day.

I do love, though, how whenever I post one of these Undeserved Reputations graphics, there’s always a cacophony of “OOOhhhh, you’re such a shill!” in the comments. You’d think that, if the information in these posts were so very wrong, there’d be a better defence than that.

I’m late to this discussion, sorry, but the major point which needs to be made about glutamate is that it’s the most commonly used neurotransmitter in the central nervous system. We have a very active and effective metabolic system for dealing with glutamate and its interconversion with glutamine, GABA and glucose. Levels are VERY tightly regulated (otherwise we’d be having seizures) and it’s naturally present at moderate levels, ore than you’d get from a meal, in all different parts of the body.
The toxicity studies by Olney were shockingly misleading – he injected a large dose of an excitatory neurotransmitter into the systemic circulation and it caused brain damage. He had to use juvenile mice to get an effect because mice are born at a time corresponding to mid-gestation in humans, when the blood-brain barrier is not yet closed. Unsurprisingly, dumping large mounts of a neurotransmitter which can cause excitotoxicity into an unprotected brain, caused cell death. The other cell death reported was in the arcuate nucleus, which, surprise, is one of the locations where the blood-brain barrier is open (to allow sensing the salt levels of blood, to guide thirst behaviour). It’s about as scientific as saying that using ink is dangerous because injecting it into the eyeball causes blindness.
So for the paranoid out there who feel glutamate is a hidden menace, rest assured that if you eliminated it from your system you would die instantly. Oh, and don’t inject neurotransmitters directly into the brain, that’s unhealthy too.

If you are really a chemist with a virtuous interest in the subject I would expect you to read all properly peer reviewed research since 1940 (not self or company published researched, or research designed to fail from the start) to form a proper opinion. Or if you lack the time, unlike me nowadays, just the clinical experiment “Deciphering the MSG controversy” S. Xiong 2009 http://www.ijcem.com. And then use your common sense, or a toxicologists opinion, to decide if it’s really such a stretch to see how MSG should be on the same list as cocaine when it comes to food additives.

It’s the opinion of multiple independent toxicologists I’ve spoken to that there’s no known harmful effect of MSG humans – well controlled studies using human subjects have failed to find any evidence. Tests in mouse cell cultures, as the study you mention detail, aren’t always good predictors of effects in humans, and we’re still yet to see anything in controlled experiments that suggest such effects exist.

If a study comes out that reliably shows MSG to have negative effects in humans, I’d certainly be rushing to edit this article. As it stands, it’s still factually accurate. Incidentally, if you truly think “MSG should be on the same list as cocaine when it comes to food additives”, I suggest you use your common sense or a toxicologist’s opinion.

Let me put it differently.

I used to be a great academic. A while ago a chef, fresh on the job, gave me and my partner a big dose of MSG. It took fifteen minutes for us to experience far more severe acute MSG symptoms than any research has ever published, we both have permanent brain damage as a result. Our inner ear synapses have been demolished leaving suicidal levels of tinnitus and noxacusis, and we suffer from constant chronic headaches. I myself, having eaten a few more bites before stopping, am unable to properly regulate my body temperature.

Now let’s come back to that common sense. Two healthy people experience severe symptoms only attributable to MSG right after eating it, and are then left with damage which can only be attributed to systemic glutamate toxicity. Naturally any other causes of possible endogenous glutamate release have been ruled out. The only thing left is several biopsies of the brain tissue that examine the specific damage over depth in several regions.
What would be the next thing you would want to research or examine to determine how this damage has occurred in the cochlea and hypothalamus?

Replicability is indeed essential in science, especially since it shows exactly when the runts doing the experiment aren’t cerebral enough to theoretically model what is going on. As it stands I find it perfectly reasonable to assume a more complex mechanism than is currently known which under certain yet normal circumstances will harm people.
An idiot chef trying to make his food taste better for hundreds of people and forgetting to stir for example. And the lack of a quantitative warning label on imported refined MSG. Let’s hope the academic medical specialists that have taken me into care are a little brighter than your acquaintances in toxicology.

Unlike many others afflicted in terrible ways by MSG I am both relentless and capable.
I consider your statement a written contract. Your lack of current sources critical of MSG can be misconstrued as an intended oversight very easily. If you want to be factually correct I submit you must add that it is very well known how, why, and when free glutamate damages the brain, and that it is not known if or how it could get there when consumed.

I hope I have impressed upon you the seriousness of the situation that I have been placed in. I am left crippled and tortured in ways you can’t imagine, having desperately tried for months to find anything other than direct MSG toxicity to match the damage to simply because the world is unwilling to value reason, knowledge, and my life above the inability to understand and replicate how ingested glutamate can damage the brain.
Now I am left to prove how and why I’ve effectively been murdered, no thanks to people that regurgitate what they believe is a critical view only after it has been explained to them.

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