The Chinese restaurant syndrome is a pattern of symptoms that affects some people after eating Chinese food. A food additive called monosodium glutamate (MSG) is involved in illness.
For many years, food additives have been used for flavoring, coloring and extension of the useful shelf-life of food, as well as the promotion of food safety. Flavoring systems are very important in savory food manufacturing.
Why do food companies add MSG to foods?
One reasons is that MSG tricks our tongue into making you think a certain food is high in protein and thus nutritious. It is not a "preservative". The food industry is trying to confuse the issue by focusing on the "fifth" taste sense they call umami. It changes our perception of not simply taste but the nutritious qualities of what we put into our mouth.
It is possible, however, that some people are particularly sensitive to food additives, and MSG is chemically similar to one of the main neurotransmitters in the brain, not surprisingly called glutamate (it is the neurotransmitter that our brain and many organs including our ears, eyes, nervous system and pancreas use to initiate processes in the body). It is 78.2% free glutamic acid, 12.2% sodium, and 9.6% water.
Some clinicians have estimated that the prevalence of “Chinese Restaurant Syndrome” may be as high 1.8% of the adult population.
The following are possible reasons for this increased MSG sensitivity:
- Genetic errors "miswire" the nervous system for glutamate receptors and synapses (because of mutations in DNA there is major expression of glutammate receptors)
- Gilbert's Syndrome - affects mainly boys - 2% of population
- Inability of liver to detoxify the blood
- NMDA glutamate receptors become sensitized
- Alcohol use which may cause:
- NMDA receptors are affected by alcohol abuse – they become sensitized. NMDA receptors are stimulated by glutamate and can be adversely affected by excess glutamate (The precise mechanism by which ethanol rapidly inhibits NMDAR function is still under investigation. However, the very fast reduction of channel activity in response to ethanol suggests a direct interaction of the NMDAR subunits with ethanol to regulate channel gating in nonneuronal mammalian cell culture models) . To compensate for chronic alcohol induced NMDA receptor inhibition, however, the number of NMDA receptors on the cells and, thus, the level of receptor activity increase after long-term alcohol exposure. So, more glutamate receptor are stimulate by excess of glutamate
- Alcohol can induce Vitamin B6 deficiency (by destroying stomach cells and by reducing absorption). Vitamin B6 is used by the body to convert amino acids. Deficiency of this vitamin will affect the body's ability to handle excess free glutamate
- Alcohol damages the liver. The liver is the major center of the body where amino acids are converted. Taurine is made there. Taurine is the major inhibitory amino acid that counters glutamate's excitatory role (by activating GABA-A receptor. The activation of GABA receptors decreases neuronal vulnerability to excitotoxic damage)
- CoQ10 Deficiency - nerve cells in the brain and else where may not have the ability to withstand the overstimulation caused by excess glutamate.
- Caused by lack of other vitamins (like Vitamin B6) the body needs to manufacture CoQ10
- Caused by stress
- Magnesium Deficiency - Magnesium is used by the nervous system to close calcium channels. MSG is a calcium channel opener
- Parkinson’s Disease
- Leads to Vitamin B6 deficiency as some medications require a patient to limit B6 intake
- Vitamin B6 deficiency caused by poor nutrition, alcohol use, or limiting this vitamin due to food/drug interactions.
- Vitamin B12 deficiency - Vitamin B12 protects against glutamate neurotoxicity
The symptoms of disease are:
* Headache, back of head and neck
* Numbness of face
* Tingling/burning of face and chest
* Tightness in chest
* Rapid heartbeat
* Nausea, diarrhea, stomach ache
* Weakness, balance problems
* Blurred vision
The symptom that occurs more frequently are migraine.
Migraine is due to different triggers, like:
- Hormonal ( period, HRT)
- Psychological (emotions, stress)
- Drugs (reserpina, estrogens)
- Ambient (altitude, smokes, noise)
- foods containing: nitrate, tiramina and glutamate or its derivates
So, Glutamate has also been described as a trigger for migraine headache exacerbations (Woods, Weiner, Abramson, Thien, & Walters, 2006). Radnitz (1990) suggested that glutamate causes a generalized vasomotor reaction, which causes throbbing pain at the temples and a throbbing sensation across the forehead. His claim derived not from a clinical trial but from an advice from the Diamond Headache Clinic. She also argued that those who experience migraine headaches are more susceptible to headache triggered by glutamate.
Leira and Rodríguez (1995)postulated that glutamate can trigger a migraine headache because of interference with acetylcholine synthesis. Glutamate acts as a precursor for the neurotransmitter acetylcholine (as well as a number of other physiological chemicals in the body). Acetylcholine reaches toxic levels in a very short period of time and acts on the brain and central nervous system. Therefore symptoms ascribed to MSG sensitivity may be caused by excessive levels of neurotransmitters such as acetylcholine.
Other less frequent symptoms are:
- Allergic response – MSG is not a true allergen but may directly affect immune response by stimulating or damaging the nervous system. In studies done recently on animals, food allergies may be caused by a lack of Interleukin 12. This substance is made by cells in the body - oligodendrocytes, that are killed by excess glutamate. For example, over 85% of individuals with Type 1 Diabetes have antibodies to the enzyme uses to turn Glutamate into GABA - glutamic acid decarboxylase (GAD). Their immune system attacks the means by which glutamate is metabolized, even though it does not attack glutamate itself. Because of their immune response to GAD, Type 1 diabetics are at risk of having an excess of glutamate in their systems already
- Digestive system – may create taurine deficiency due to its effect on cysteine. Cysteine competes with glutamate for uptake. Unfortunately, cysteine is used to make taurine, and taurine is used to make bile. Bile, which is made by the liver and stored in the gall bladder is used to break up fats into manageable pieces for digestion. If bile formation is compromised - diarrhea and "gall bladder attacks" may occur
- Hearing - The hair cells of the ear use glutamate as a neurotransmitter. Over-stimulation of these cells by glutamate can result in ringing in the ears. Glutamate opens calcium channels
- Lungs - "Asthma"http://www.ncbi.nlm.nih.gov/pubmed/9648703 - due to MSG’s stimulatory effect on the nervous system would explain why asthma is induced in some by MSG
The Chinese restaurant syndrome is not particularly severe. In fact, the symptoms tend to regress spontaneously and there are not complicances. The people who suffer from this disease may avoid to avoid Chinese restaurants or consume foods rich in glutamate monosodic.
Luigi Ludovico Carucci