"Chinese Restaurant Syndrome" 
Monosodium glutamate (MSG) is a flavor enhancer commonly added to  Chinese food, canned vegetables, soups and processed meats. Although the  Food and Drug Administration (FDA) has classified MSG as a food  ingredient that's "generally recognized as safe," the use of MSG remains  controversial. For this reason, when MSG is added to food, the FDA  requires that it be listed on the label.  
 MSG is ubiquitous in processed foods, such as soups, luncheon meats,  meat tenderizers, seasoning salt, snack foods, salad dressings, fast  foods and frozen dinners. It is estimated that as much as 500 million  pounds of MSG are added to the world food supply each year. 
Now a report focuses on how monosodium glutamate may be just                   one of the causes of the Slow Poisoning.
In fact, MSG (which is often disguised by names like  "hydrolyzed vegetable protein" or "HVP", "yeast extract" or "autolyzed  proteins") is, like aspartame,  a member of the group of chemicals known as "excitotoxins" (the clue is  in the name!).  These toxic compounds are known to interfere with brain  chemistry and have been implicated in many neurological diseases, such  as brain cancers, MS, fibromyalgia, depression and hyperactivity (ADHD).  In fact, they overexcite brain cells to the point of cell damage and  even cell death. 
MSG has also been linked to obesity and, indeed, many products that  contain MSG now also contain horrific chemicals like "high fructose corn  syrup" (whose purpose is to make you chemically addicted to the food in  the same way as sugar).   
Monosodium glutamate is the sodium salt of                     the amino acid glutamate, and is a commonly used flavor                     enhancer, regarded by the FDA as "generally safe", meaning                     that food manufacturers can use as much of it as they like.  It                     has been around for many years, and is found not only in                     take away meals from Chinese restaurants, but many other                      food sources, in which it is listed as either "monosodium                     glutamate", "MSG" or "hydrolyzed vegetable protein".
In a recent book on the subject, Dr  Russell Blaylock reported that MSG also causes severe disturbances in  the endocrine system, affecting levels of hormones such as LH  (Leutenising hormone), GH (growth hormone) and prolactin. (Excitotoxins by Russell L Blaylock MD, page 263) 
 
Another recent work stated that "The  stress-induced abnormalities in blood-brain barrier permeability suggest    differing MSG effects dependent on existing states of relaxation or  stresses.   The suggestive evidence for MSG-induced neuroendocrine  effects is substantial,   coupled with the observation of increased  obesity in children." (                 In Bad   Taste by George R Schwartz MD, page 39)
What are the symptoms of sensitivity?
There is no doubt that  some people have a sensitivity to monosodium glutamate, and will  experience any or all of the following symptoms when they consume it:
Headache, Weakness, Heart palpitations, Flushing, Extreme thirst, Anxiety, Nausea and Numbness.  Those with asthma seem to be particularly susceptible to MSG sensitivity.
One rule of thumb is that, if the packaged food comes with a "flavor  packet" it probably contains MSG. Also, most frozen dinners and entrees  contain monosodium glutamate in some form, usually as hydrolyzed protein  or autolyzed yeast.   In short, MSG is a leading cause of obesity and may well be implicated in  many other conditions. It should be avoided at all costs, just like its  chemical relatives.  
Eat and be healthy with my warmest regards.