Is MSG Unhealthy? The 'MSG Symptom Complex'

Although Nontoxic, MSG May Cause Weight Gain

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Awhile back, my wife and I went out for a night on the town and started with dinner at a new American-Chinese restaurant.  We had never before been to the restaurant so we took a quick look at the menu before we committed.  After looking at the menu -- which appeared pretty standard for American-Chinese fare -- we noticed a sign about MSG that persuaded us to eat elsewhere.  The sign touted how all the food was "free of MSG."  My wife and I love or MSG -- the stuff is delicious.

  At home, we use MSG to salt everything from stir fry to hash.

Monosodium glutamate or MSG is the sodium salt of the common amino acid glutamate.  Glutamate is naturally found in protein food sources which we consume every day.  Furthermore, flavor-enhancing MSG was first isolated from a very natural source: seaweed broth. 

Monosodium glutamate is found in countless processed and packaged foods including soy sauce, cold cuts, gravies and potato chips.  The average human being eats 13 grams of glutamate a day derived from protein found in food with 0.55 grams attributable to MSG itself.

If you're a Gen Xer like me, you may remember hearing about how MSG--stereotypically, MSG found in American-Chinese food--is a carcinogen, causes allergic-type reactions and so forth.  However, various studies reviewed by the FDA, WHO, and other medical organizations around the world have repeatedly shown that MSG is nontoxic.

  In fact, after much consideration, the FDA has labeled MSG with the "generally recognized as safe" distinction. 

Even though MSG is nontoxic, it may still be unhealthy.  Specifically, some research indicates that MSG is linked to weight gain.

The 'MSG Symptom Complex'

Some refer to the MSG symptom complex as "Chinese restaurant syndrome," a pejorative term which stereotypically targets American-Chinese or Chinese food as causative which is untrue.

  As previously mentioned, MSG is a food additive found in a wide variety of foods. 

After eating food salted with MSG, some people have complained of the following symptoms shortly after consumption:

  • neck, chest, and forearms burning sensations;
  • facial tightness;
  • dizziness;
  • upper body tingling;
  • upper body weakness;
  • heart palpitations;
  • numbness in the back, neck and arms;
  • headaches;
  • bronchospasm in people with asthma;
  • drowsiness.

Randomized control trials testing MSG have failed to consistently trigger such symptoms in research participants which make the MSG symptom complex unlikely in the vast majority of people.  Moreover, the FDA questions whether MSG can cause bronchoconstriction in people with asthma.  However, in a small subgroup of people, such symptoms were triggered by exposure to 3 grams of MSG in the absence of food.  

Keep in mind that it's doubtful that anybody sits around and ingests 3 grams of MSG by itself especially if she knows it makes her sick.  (Although, one time, I did mistake the MSG in our cabinet for sugar.

  Threw that cup of coffee away real quick!)  Furthermore, the carbohydrates in food are believed to dampen the effects of MSG.

MSG and Obesity

Animal studies have shown that mammals (like humans) can metabolize relatively large amounts of glutamate without a significant rise in plasma or blood levels.  Furthermore, high levels of glutamate don't cross the placenta, and even if they were able to, human infants can metabolize glutamate just as well as adults.  Thus, the prospect that birth defects occur secondary to glutamate is remote.  Finally, glutamate fails to cross the blood-brain barrier thus greatly reducing exposure of the central nervous system to glutamate.  In fact, the only places where the central nervous system is exposed to glutamate are circumventricular organs with fenestrated or leaky capillary systems.

However, one leaky area of the central nervous system which some researchers hypothesize may experience nerve damage secondary to glutamate or MSG is the pituitary gland.  The pituitary gland or the body's "master gland" controls many of the body's other hormone glands such as the adrenals and thyroid. 

With respect to obesity, researchers hypothesize that brain damage to the hypothalamic-pituitary axis caused by MSG could mess with the way people react to leptin.  Leptin is a hormone which triggers satiety or fullness.  Of note, this hypothesis seems to be supported in rodent studies.

Another study in rodents suggested that MSG may somehow upregulate adipsin, an adipokine secreted by adipocytes or fat cells.  This presence of more adipsin could cause weight gain, too.

It should be noted that, at this point, hypotheses about MSG affecting leptin and adipsin, and thus resulting in obesity are merely hypotheses without any direct proof in humans.  Nevertheless, a large Chinese cross-sectional study that controlled for energy intake (food consumption) and physical activity and exercise found a positive correlation between MSG consumption and weight gain.  In other words, people who eat more MSG could gain more weight, too.  Obviously, much more research needs to be done in order to suss out any causation.

Conclusion

So where does all this conjecture, postulating and research leave us?  I don't know about you guys, but I'm still going to use MSG to prepare the food that I consume.  Even though it might be unhealthy, MSG exposure is a risk that I'm willing to take in return for more sumptuous victuals.  Nevertheless, if you are worried about weight gain caused by MSG, or, worse, are concerned that MSG makes you dizzy, nauseated or any of the other symptoms listed as part of the MSG symptom complex, please steer clear of the stuff.  Keep in mind that the FDA requires food labels to list ingredients on food labels.

Selected Sources

Article titled "Association of Monosodium Glutamate Intake With Overweight in Chinese Adults:
The INTERMAP Study" by K He and co-authors published in Obesity in 2008.  Accessed on 3/8/2015.

Article titled "The Safety Evaluation of Monosodium Glutamate" by R Walker and JR Lupien published in The Journal of Nutrition in 2000.  Accessed on 3/8/2015.

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