Excitotoxicity is the pathological process by which nerve cells are damaged or killed by excessive stimulation by neurotransmitters such as glutamic acid (glutamate).
In 1969 when researcher Dr. John Olney of Washington
University in St. Louis observed that process in his laboratory, it should have resulted in sweeping changes
in how food additives are regulated.
He noted that glutamate fed as monosodium glutamate (MSG) to laboratory animals
killed brain cells and subsequently caused gross obesity, reproductive
dysfunction, and behavior abnormalities.
Before that, the world knew nothing of what Dr. Olney had
dubbed “excitotoxins.” And after Olney’s discovery, the existence of free excitotoxic
amino acids present in food became the best-guarded secret of the food and drug
industries.
Today, excitotoxins present in food remain largely ignored
or unknown, mostly because the rich and powerful food and pharmaceutical industries
want it that way. A great deal of food industry profit depends on using excitotoxins
to “enhance” the taste of cheaply made food. And a great deal of pharmaceutical
industry profit depends on selling drugs to “cure” the diseases and disabilities
caused by the excitotoxins in the food supply.
What
are excitotoxins?
Excitotoxins are often amino acids, but not all amino acids are excitotoxins. The amino acid with the greatest excitotoxic footprint is glutamate. When present in protein or released from protein in a regulated fashion (through routine digestion), glutamate is vital to normal body function. It is the major neurotransmitter in humans, carrying nerve impulses from glutamate stimuli to glutamate receptors throughout the body. Yet, when present outside of protein in amounts that exceed what the healthy human body was designed to accommodate (which can vary widely from person to person), glutamate becomes an excitotoxic neurotransmitter, firing repeatedly, damaging targeted glutamate-receptors and/or causing neuronal and non-neuronal death by over exciting those glutamate receptors until their host cells die.
Technically speaking, neurotransmitters that over-stimulate
their receptors to the point of killing the cells that host them are called excitotoxic
neurotransmitters, and the resulting condition is referred to as
excitotoxicity. Glutamate excitotoxicity is the process that underlies the
damage done by MSG and the other ingredients that contain processed free
glutamic acid (MfG).
Glutamate is called a non-essential amino acid because if
the body does not have
sufficient quantities to function normally, any needed glutamate can be produced
from other amino acids. So, there is no need to add glutamate to the human diet.
The excitotoxins in MSG and other ingredients that contain MfG are not needed
for nutritional purposes. MSG and many other ingredients have been designed to
enhance the taste of cheaply made food for the sole purpose of lining the
pockets of those who manufacture and sell them.
Glutamate neurotransmitters trigger glutamate receptors
both in the central nervous system and in peripheral tissue (heart, lungs, and
intestines, for example). After stimulating glutamate receptors, glutamate neurotransmitters
may do no damage and simply fade away, so to speak, or they may damage the
cells that their receptors cling to, or overexcite their receptors until the cells
that host them die.
There’s another possibility. There are a great many
glutamate receptors in the brain, so it’s possible that if a few are damaged or
wiped out following ingestion of MfG, their loss may not be noticed because
there are so many undamaged ones remaining. It is also possible that
individuals differ in the numbers of glutamate receptors that they have. If so,
people with more glutamate receptors to begin with are less likely to feel the
effects of brain damage following ingestion of MfG because even after some
cells are killed or damaged, there
will still be sufficient numbers of undamaged cells to carry out normal
body functions.
That might account for the fact that some people are more
sensitive to MfG than others.
Less is known about glutamate receptors outside the brain –
in the heart, stomach, and lungs, for example. It would make sense (although
that doesn’t make it true) that cells serving a particular function would be
grouped together. It would also seem logical that in each location there would
be fewer glutamate receptors siting on host cells than found in the brain, and
for some individuals there might be so few cells with glutamate receptors to
begin with, that ingestion of even small amounts of MfG might trigger asthma,
atrial fibrillation, or irritable bowel disease; while persons with more cells
hosting glutamate receptors would not notice damage or loss.
Short-term effects of excitotoxic glutamate (such as asthma
and migraine headache) have long been obvious to those not influenced by the
rhetoric of the glutamate industry and their friends at the U.S. Food and Drug
Administration. Hopefully, researchers will soon begin to correlate the adverse
effects of glutamate ingestion with endocrine disturbances such as reproductive
disorders and gross obesity. It is well known that glutamate plays an important
role in some mental disorders and neurodegenerative diseases, but the fact that
ingestion of excitotoxic glutamate might contribute to existing pools of free
glutamate that could become excitotoxic,
still needs to be considered. Finally, a few have begun to realize the
importance of glutamate’s access to the human body through the mouth, nose and
skin.
There are three excitotoxic amino acids used in quantity in
food, cosmetics, pharmaceuticals,
protein drinks and powders, and dietary supplements:
1) Glutamic acid — found in flavor enhancers, infant
formula, enteral care products for invalids, protein powders, processed foods,
anything that is hydrolyzed, and some pesticides/fertilizers.
2) Aspartic acid — found in low-calorie sweeteners,
aspartame and its aliases, infant formula, protein powders, anything that is
hydrolyzed, and
3) L-cysteine — found in dough conditioners.
According to Dr. Edward Group, the six most dangerous
excitotoxins are: MSG (monosodium glutamate), aspartate, domoic acid, L-BOAA,
cysteine, and casein.
Resources
Dr. Edward Group The 6 Most Dangerous Excitotoxins. Global
Healing Center. (accessed 8/20/2016)
Blaylock RL. Excitotoxins: The Taste That Kills. Santa Fe, New Mexico: Health Press; 1994.
Olney JW. Brain Lesions, Obesity, and Other Disturbances in Mice Treated with Monosodium Glutamate; Science. 1969;164:719-21.
Olney JW, Ho OL. Brain damage in infant mice following oral intake of glutamate, aspartate or cystine. Nature. 1970;227:609-611.
Olney, J.W. Excitatory neurotoxins as food additives: an evaluation of risk. Neurotoxicology 2: 163-192, 1980.
Olney JW. Excitotoxins in foods. Neurotoxicology. 1994 Fall;15(3):535-44.
Gudiño-Cabrera G, Ureña-Guerrero ME, Rivera-Cervantes MC, Feria-Velasco AI, Beas-Zárate C. Excitotoxicity triggered by neonatal monosodium glutamate treatment and blood-brain barrier function. Arch Med Res. 2014 Nov;45(8):653-9.
Verywellhealth.com.
An Overview of Cell Receptors and How They Work https://www.verywellhealth.com/what-is-a-receptor-on-a-cell-562554 (Accessed 5/5/2019)