Skeptical Raptor's Blog hunting pseudoscience in the internet jungle

MSG-myth versus science


No-MSG2Update of 31 December 2012 article

Food additives are one of the most passionate issues amongst people who eat (which would be everyone). AspartameHigh fructose corn syrup. GMO‘s. Salt. Sugar. Trans fats. Polysorbate 80. Some of the angst caused by these additives is that they have scary chemical names. Obviously the “low fructose corn syrup” has got to be better? Right?

But there is one food additive that appears to be the root of all evil–MSG. How many times have you been to a Chinese restaurant where they put up signs with NO MSG ADDED? Just so you know, unless that restaurant isn’t using soy sauce (one of the major components of nearly all Chinese food flavorings), the amount of MSG in your Kung Pao Chicken is still quite high, because that soy sauce has more MSG in it than could possibly be added by a shaker of MSG.

Background

MSG has no taste by itself, but it is used by many professional cooks as a flavor enhancer, improving and enhancing the flavor of almost any food. The taste that is enhanced by MSG is different than the standard sour, sweet, bitter and salt flavors–it is called “umami,” which also is enhanced by substances like soy sauce. It’s the savory flavor that one finds that is different from the commonly stated “four tastes” that chefs used to consider when developing flavors for food. The taste enhancing quality of MSG is not well understood, but it’s possible that humans evolved the pleasurable taste of umami as a result of natural selection favoring those who enjoy eating high quality protein foods.  

MSG has been used as a flavor enhancer for several thousand years. It is one of the key components of many Asian cuisines, especially Japanese who have extracted MSG from kelp for centuries. The Romans used a sauce called garummade from fermented fish, that was used instead of more expensive salt. In fact, MSG can be used to mask bad flavors, such as spoiled meat, just like salt. 

Myth

The myth of MSG probably started with personal anecdotes after eating Chinese food. A 1969 article in Science claimed there was a dose-response relationship between Chinese food and the Chinese Restaurant Syndrome (CRS).  But the study did not isolate MSG as the cause, and was not blinded (which would be nearly impossible if were to determine if the cause was the food rather than the ingredients).  Unfortunately, the study has never been repeated, so it’s impossible to determine if it provides evidence that Chinese food does anything, let alone MSG.

Joe Mercola, one of the leading purveyors of nonsense science and medicine, calls MSG “the silent killer lurking in your kitchen cabinets.” Oh my. His claims are based on a belief that MSG is an excitotoxin, which causes a pathological process by which nerve cells are damaged and killed by excessive stimulation by neurotransmitters. This pseudoscience is promoted by  Dr. Russell Blaylock, a board-certified neurosurgeon and author of “Excitotoxins: The Taste that Kills.” Setting aside the Appeal to Authority (a board certified neurosurgeon may not have any actual knowledge of neurochemistry), a book isn’t necessarily a high quality source.

Mercola pushes a belief that MSG overexcites your nerve cells to the “point of damage or death, causing brain damage to varying degrees — and potentially even triggering or worsening learning disabilities, Alzheimer’s disease, Parkinson’s disease, Lou Gehrig’s disease and more.” Oh my!

But Mercola doesn’t stop there. He also believes that MSG causes obesity, eye damage, headaches, fatigue, disorientation, depression, and a whole host of other maladies. And he states that up to 40% of the US population may be impacted by MSG. OH MY!

Science

First, what exactly is MSG. This is the point that makes many scientists laugh, because MSG is simply the sodium salt of glutamic acid, an amino acid which is the building block of proteins. You get glutamic acid from almost every food you eat from grains to meat. Some grain proteins have over 30% by weight glutamic acid. Since glutamic acid doesn’t exist except in the presence of water, it precipitates with sodium or other cations (potassium, lithium, and others).  Hence, the “monosodium” part of MSG. 

Here’s the actual science behind glutamates (you can ignore this paragraph, if chemistry makes your eyes glaze over). When glutamic acid or one of its salts is dissolved in aqueous solutions, a pH-dependent instantaneous chemical equilibrium of the amino acid’s ionized forms, including zwitterionic forms, will result. These forms are called glutamates. Salts exist only in a dry and crystallized form. The form ultimately responsible for the taste is the glutamate ion, and the form of glutamic acid at the time of the addition is not important. However, crystalline glutamic acid salts such as monosodium glutamate dissolve much better and faster than crystalline glutamic acid, a property important for use as a flavor enhancer.

Glutamic acid, one of the amino acids upon which every single protein is built in the human body, is chemically indistinguishable from the acid salt, MSG. Once you ingest MSG, it dissociates into sodium and the glutamate, which will be absorbed and utilized by the body. Glutamic acid does not suddenly change properties when in salt form. Once it’s consumed, the glutamate separates from the sodium, and binds with hydrogen to become an acid again. The sodium is either utilized by the body or excreted through the kidneys.  It’s a simple physiological process, no mystery at all.

The body produces glutamate (or glutamic acid more properly) during various cellular processes, including the citric acid cycle, or Kreb’s cycle, which is a complex metabolic system fundamental to how the cell builds proteins and provides energy. Glutamate is also a key compound in eliminating and controlling the waste nitrogen in the body (which is created by cells in the form of urea). It is also a neurotransmitter, used by nerve cells to transmit certain types of information, and is a critical substance in cognitive functions in memory and learning.  In other words, glutamate is very important to your life.  Without it, you will probably die. Or at least not be able to think.

So if you eat a lot of glutamate in your food, and your body synthesizes glutamate in substantial quantities, what is bad about MSG. Well, there’s a couple of issues that might happen. MSG does have a sodium, but it’s actually less by weight than an equivalent amount of table salt. Interestingly, in a 1984 Journal of Food Science article, MSG may actually be useful in reducing sodium consumption while not compromising taste (salt is critical to taste of many savory foods).  

But is there any evidence that MSG is dangerous to humans?  In a word, no.

These review articles, which are meta-analyses of a large number of primary research articles, along with clinical trials, just don’t support the myth that MSG has an effect on anyone. There might be a small subpopulation of people who are sensitive to MSG, but even that has little support in scientific evidence, and is completely dismissed in systematic reviews.

It is possible that Chinese food itself causes CRS. The food is saltier. It is filling. It can be high in carbohydrates and oils. In other words, other substances within the food may have the same exact effect as what is claimed by MSG alone. Funny thing is that soy sauce is higher in free glutamate (as discussed above, the form of MSG in solution) than what is used by most cooks. So are tomatoes. So are dozens of other foods.

In fact, according to a report by Food Standards Australia New Zealand, a typical Chinese restaurant meal will have between 10-1500 mg glutamate per 100 g food. Soy sauce has 400-1200 mg/100g. Vegemite (for my Australian readers) has about 1400 mg/100g. Parmesan cheese has around 1200 mg/100g. Tomatoes have around 200 mg/100g. In other words, your typical Italian meal (with tomato sauce and Parmesan) may provide more glutamate than your typical Chinese meal. 

Almost everyone you hear who claim an MSG sensitivity do not base that on anything but their personal experience. An anecdote. They remember the one time that they might have had MSG, but forget all the times they felt fine after having sushi with soy sauce. Or a BBQ sauce that contains soy sauce and tomato sauce.  

MSG is perfectly safe.  Go have a spoonful. Or put it on your food, because it does make it tastier.

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