Food-borne Neurotoxins and Tinnitus
Part 2: Monosodium Glutamate

by Barry Keate

Last month I wrote about the effects of Aspartame (aspartate) on the brain and degenerative neurological conditions. We looked at the many ways Aspartame affects brain function, destroys neurons and contributes to many neurological diseases such as MS, epilepsy, chronic fatigue syndrome, Parkinson’s disease, Alzheimer’s disease and tinnitus.

This month we are going to look at a related substance, Monosodium Glutamate (MSG) found in many prepackaged food products. MSG breaks down into glutamate in the body. Glutamate, like aspartate, is an excitatory neuro-transmitter; it triggers the firing of neurons. When there is too much glutamate in the synapse between neurons, it activates the neurons into a continual firing mode until they exhaust their energy reserves and die. For this reason many researchers refer to these excitatory neurotransmitters as excitotoxins.

For thousands of years Japanese cooks have added a special ingredient to their recipes to magnify the desired taste of foods. This ingredient was made from a sea weed known as “sea tangle” or kombu. Yet it was only in the twentieth century that the active ingredient in kombu was isolated. This ingredient was Monosodium Glutamate.

Shortly after isolating the compound, the chemists who discovered MSG turned it into a worldwide multi-million dollar enterprise. They founded the Ajinomoto Company in Japan which today produces most of the world’s supply of MSG and a related taste-enhancing substance called “hydrolyzed vegetable protein,” which also contains large amounts of MSG.

After World War II, American food manufacturers discovered the flavor enhancing virtues of MSG and began adding it to processed foods, including baby food. It was thought at the time to be perfectly harmless and natural, since it was an amino acid. The amounts of MSG added to foods have doubled every decade since the 1940’s. By 2000, 350,000 metric tons of MSG were produced.

Glutamate is the primary villain in cochlear-synaptic tinnitus. This type of tinnitus develops when hair cells in the cochlea are damaged. This is caused primarily by exposure to loud noise or ototoxic drugs which damage the hair cells. When the hair cells are damaged, they release large amounts of glutamate which become toxic to the neuroreceptors in the auditory pathway. These receptors die off from the excess glutamate and tinnitus is the result.

Here is a brief overview of the process leading to neuron death. The electrical connections in the brain and auditory pathway, the synapses, are constantly stimulated or inhibited by neurotransmitters. Two of the main stimulating (excitatory) transmitters are glutamate and aspartate while the primary inhibitory transmitter is gamma-amino-butyric acid (GABA). If these neurotransmitters become out of balance, neurological problems develop.

When glutamate or aspartate surrounds the synapse, it opens the sodium channel in the neuron. The influx of sodium causes the nerve to fire. When exposed to excessive levels of excitotoxins, the sodium channel in the neuron is forced to remain open. Sodium continues to flow into the neuron causing it to continue firing. This continuous firing of the neuron causes a rapid buildup of free radicals and inflammatory products. These compounds attack the mitochondria, the energy producing elements in the core of the neuron cell. The mitochondria become depleted and the neuron withers and dies.

We know that people with tinnitus have an excess of neuronal firing in the auditory cortex and that by activating GABA receptors tinnitus can be reduced. This can be accomplished by the medication Neurontin which activates these receptors. An article on this subject can be viewed here.

Early warning signs of the dangers of MSG began to surface in the 1950’s. Two ophthalmologists decided to test MSG on infant mice in an effort to study an eye disease. When they later examined the eye tissues of the animals, they made a startling discovery. The MSG had destroyed all of the nerve cells in the inner layers of the animal’s retina, which are the visual receptor cells of the eye.

Some ten years later, John Olney, MD, a neuroscientist, repeated the experiment. He found that MSG was not only toxic to the retina, but also to the brain. When he examined the animals’ brains, he discovered that specialized cells in a critical area of the brain, the hypothalamus, were destroyed after a single dose of MSG.

Dr. Olney, one of the leading researchers in this area, informed the FDA of the very real dangers MSG posed in baby food but they refused to listen. Only after he testified before a Congressional committee did the food manufacturers agree to remove MSG from baby foods. As we shall soon see, that did not really happen.

In the 1960’s, the term “Chinese Restaurant Syndrome” appeared in the popular vocabulary. This syndrome occurred frequently in people who ate in Chinese restaurants, notorious for their heavy use of MSG. It is characterized by a set of symptoms which include sudden onset of headache, heartburn, palpitations, sweating, swelling, and flushing of the face. MSG was beginning to develop a poor reputation and many people were attempting to minimize exposure to this food additive.

FDA labeling restrictions state that MSG must be listed on a product label only when it is added in its free form. If it is combined with other food compounds, it does not have to be listed separately. This loophole in labeling requirements led to the development of “hydrolyzed vegetable protein”, sometimes referred to simply as “vegetable protein”, “plant protein” and even “natural flavoring”.

Hydrolyzed vegetable protein is manufactured from “junk” vegetables no longer fit for retail sale. The vegetables are boiled in sulfuric acid for several hours then neutralized using caustic soda. A brown sludge rises to the surface of the mixture. This is scraped off, dried and powdered, after which MSG is added, typically in the range of 40-60%. It is then added by the food industry to everything from canned tuna to baby food. This happens without any mention of MSG on the label.

Excitotoxins, such as MSG and Aspartame, have been linked to a whole group of degenerative brain diseases in children and adults, especially the very young and the elderly. These diseases include ADD and ADHD, Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, ALS, (Lou Gehrig’s disease), as well as several more rare disorders of the nervous system. Tinnitus is a degenerative neurological condition that is affected by excitotoxins.

What all of these diseases have in common is a slow destruction of brain cells that are specifically sensitive to excitotoxin damage. Neurons that use glutamate for a transmitter are destroyed by high levels of glutamate, while neurons that use other transmitters are spared.

While there is little evidence that food-borne excitotoxins are the cause of these disorders, there is growing evidence that they can aggravate these conditions and that they may even precipitate them in sensitive individuals. Certainly the scientific evidence is far too strong to ignore the possibility that excitotoxic food additives may cause such conditions to appear sooner and to a more serious degree.

As we ended the article last month, we will state again: In order to maintain good health and reduce effects of tinnitus and other neurological conditions it is extremely important to enjoy a healthful diet. We should strive to eat whole foods, whenever possible, avoid prepackaged and processed foods including soft drinks and especially diet soda. We should reduce our intake of salt and high glycemic foods such as simple sugars and refined carbohydrates.

For more information on how to prevent or reduce neurological disease I highly recommend the book “Excitotoxins: The Taste that Kills” by Russell Blaylock, MD. Dr. Blaylock is a board certified neurosurgeon with 21 years of experience and is a clinical assistant professor at the University of Mississippi Medical Center.

Next month we will discuss a number of dietary supplements that can be used to prevent neurological damage and help restore healthy brain function in those already afflicted. These supplements include Ginkgo biloba, zinc, Omega-3 fatty acids, Acetyl-L-Carnitine, Alpha Lipoic Acid, Coenzyme Q10 and N-Acetyl-Cysteine.

Additives that always contain MSG:

Hydrolyzed Vegetable Protein
Hydrolyzed Protein
Hydrolyzed Plant Protein
Plant Protein Extract
Sodium Caseinate
Calcium Caseinate
Yeast Extract
Textured Protein
Autolyzed Yeast
Hydrolyzed Oat Flour

Additives that frequently contain MSG:

Malt Extract
Malt Flavoring
Bouillon
Broth
Stock
Flavoring
Natural Flavoring
Natural Beef or Chicken Flavoring
Seasoning