Excitotoxins --- The Taste That Kills
Russell L. Blaylock, M.D.
(264 pp., $27.00, ISBN: 0-929173-14-7, Santa Fe, NM, Health Press, 1994)
What do monosodium glutamate (MSG), hydrolyzed vegetable protein and Aspartame (Nutrasweet) all have in common? They are all common taste-enhancing additives found in a variety of foods and beverages, and they all contain Excitotoxins. In his book, Excitotoxins --- The Taste That Kills, Dr. Russell L. Blaylock provides an extensive review of the literature supporting his hypothesis that these excitatory amino acids can promote death of neurons in the brain and spinal cord. Dr. Blaylock defines excitotoxins as a "group of excitatory amino acids that can cause sensitive neurons to die." The most common ones are glutamate, aspartate, and cysteine.
Dr. Blaylock is in private practice and is a board-certified neurosurgeon, clinical assistant professor at the University of Mississippi Medical Center, and President of the Mississippi Chapter of the Association of American Physicians and Surgeons (AAPS). His book tackles a very complex and controversial topic. Much of the research he reviews seems to support the age-old adage, "you are what you eat." The discussion of mechanisms of neuronal cell death and their relation to excitotoxins is detailed and well-referenced, yet is written in such a fashion the non-medical person will come away with a good understanding of the subject. Numerous illustrations, drawn quite expertly by the author himself, enhance the understanding of the gross and microscopic anatomy and membrane transport mechanisms involved.
Although excitotoxins are widely distributed in our food supply, the author points out we may not be able to depend upon the Food and Drug Administration (FDA) to protect us from these toxic, excitatory amino acids. The author tells us that a powerful food lobby, known as the Glutamate Association, works diligently to counteract any negative reports or publicity. In reviewing the "glutamate story," Dr. Blaylock reveals that the FDA was made aware of research showing MSG added to baby food posed a danger to developing infants. Yet, it required Congressional testimony by a dedicated scientific researcher before MSG was removed from all baby foods. The author also reviews some of the problems he sees with research data purportedly showing the safety of MSG --- research which was funded by the glutamate industry. His discussion of truth in scientific research and bias (based on source of grant support) is quite thought-provoking, and it remains a concern for many of us who are faced with trying to interpret scientific studies in many areas of medicine today. He also points out new labeling guidelines promulgated by the FDA allow many of these excitotoxins to be disguised using such benign sounding names as "natural flavoring." This makes it even more difficult for the consumer to tell what the product actually contains.
The very young and the very old appear to be most susceptible to the deleterious effects of excitotoxins. A built-in protective mechanism known as the blood brain barrier excludes many of these substances from the central nervous system to some degree. The blood brain barrier, however, is not fully developed in the very young, and it can be damaged by a variety of brain insults that are common and often asymptomatic in older people. Those with neuro-degenerative conditions or those who are at risk for developing conditions such as Parkinson's disease, Huntington's chorea, Alzheimer's disease and Amyotrophic Lateral Sclerosis (ALS), may be especially vulnerable to the toxic effects of glutamate and Aspartame (Nutrasweet). Those who have suffered strokes may also be at high risk because of disruption of the blood brain barrier. Various common metabolic conditions including hypoglycemia and hypoxia also place people at risk due to dysfunction of energy --- requiring, protective, cell transport mechanisms.
The damage produced by these excitotoxins seems to selectively involve areas of the brain which have a high density of glutamate receptors. This includes important structures like the hypothalamus and the hippocampus. The former structure is, in turn, involved in the regulation of many important endocrine functions in the body, and the latter structure is intimately involved in memory function. Nerve cells in the substantia nigra (Parkinson's disease) and anterior horn cells in the spinal cord (ALS) are also susceptible to damage via glutamate toxicity.
The author develops his hypothesis noting that neuronal damage caused by excitotoxins may be rather insidious, occurring over many years. The brain has a rather remarkable ability to compensate for nerve cell damage and cell loss so that many diseases are not clinically apparent until a very high percentage of cells have been lost. This is particularly relevant in the case of such diseases as Parkinson's and Alzheimer's disease. He suggests there may be few, if any, signs of a clinical problem at the time excitotoxin damage is occurring during the course of one's lifetime.
Although the author suggests a number of things which the FDA could do, including requiring that MSG and other food additives be specifically listed on the product, he stops short of advocating a total ban of these flavor-enhancing substances. It is clear unbiased research in this area should be presented in an open forum setting so that people can be informed and thus be able to make up their own minds about the safety of these compounds. Dr. Blaylock's book on Excitotoxins goes a long way toward accomplishing this goal and serves to disseminate this important information to the public.
Reviewed by Lawrence R. Huntoon, MD, PhD
Dr. Huntoon, a board-certified neurologist with a Ph.D. in physiology (neurophysiology), practices in Jamestown, New York, and is a member of the AAPS Board of Directors.