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Volume 37, No. 1

Review of: Excitotoxins: The Taste that Kills

Russell L. Blaylock, MD, has written Excitotoxins: The Taste that Kills,1 in which he explains that certain amino acids when overly abundant in the brain can cause neurons to die. Many biochemicals can act as neurotransmitters in the brain—some excite our neurons; others calm them. In particular, glutamate, aspartate, and cysteine are three amino acids that excite our neurons and can be called "excitotoxins." They are now added in large amounts to our food supply.

Glutamate, as monosodium glutamate (MSG) is added to many foods. It excites our taste buds and can make bland food taste wonderful. It is contained in the sea vegetable, kombu, which has been used as a flavor enhancer "for thousands of years in Japan." In 1908 a Japanese scientist discovered that glutamate is the active chemical in kombu. By 1933 their annual consumption of monosodium glutamate was over ten million pounds. Japanese cooks had found that MSG made even the most bland recipes "taste scrumptious." In the Second World War it was used in the rations for the Japanese soldiers. "Unlike American rations, theirs tasted delicious." Soon the American food industry was following the lead of the Japanese and using MSG. "The use has doubled every decade since the late 40's. Today MSG is added to most soups, chips, fast foods, frozen foods, ready-made dinners, and canned goods. And it has been heaven sent for the diet food industry, since so many of the low-fat foods are practically tasteless. . . . Often MSG and related toxins are added to foods in disguised forms. For example, among the food manufacturers favorite disguises are 'hydrolyzed vegetable protein,' 'vegetable protein,' 'natural flavorings,' and 'spices.' Each of these may contain from 12 per cent to 40 per cent MSG."

The human brain has two excellent natural methods of control: (1) balance the chemicals within and (2) selectively screen the chemicals allowed inside. Glutamate is an amino acid that is used extensively in our brains. Why would it be toxic? Unfortunately, sometimes these two natural control methods break down.

Energy, Magnesium, and Antioxidants
First, in the brain the correct balance is maintained by excellent processes for reducing excess glutamate (or glutamic acid) at the special glutamate receptors in many neurons. Some processes involve storing the extra glutamate in nearby glia cells. Activating the appropriate enzymes for this process requires a great deal of energy, which, if unavailable, will result in the continual exposure of the neurons to the excitatory glutamate, injuring them and finally, if the energy deficit persists, the neurons will die. Other protective processes involve sufficient magnesium to block the uptake of glutamate by the neurons and also sufficient antioxidants, such as glutathione and vitamins C and E, to dispose of the free radicals generated within the neurons by the excitotoxins such as glutamate, aspartate, and cysteine. The powerful antioxidant glutathione consists of two of these excitotoxins, cysteine and glutamic acid, plus glycine. However, glutathione can only be formed from these amino acids when magnesium, potassium, and sufficient energy are all present.

When free radicals are not quenched they can stimulate the release of more excitotoxins from storage. "This produces a vicious cycle whereby excitotoxins stimulate free radical formation and the free radicals in turn stimulate further excitotoxin accumulation." We need to be careful to have sufficient antioxidants and magnesium in our diet!

Blood-Brain Barrier
The second major way in which the neurons are usually protected involves the circulatory system in the brain, which has blood vessel walls that allow certain chemicals to enter the brain while excluding others—the so-called blood-brain barrier. "There is a tight junction between the cells. . . that line the capillary walls. Blood vessels in other parts of the body have relatively large spaces between the cells that allow the passage of even large molecules." Fortunately, antioxidants such as vitamins C and E can pass through the blood-brain barrier. Dr. Blaylock points out that this barrier is not well developed in the very young and it may even be still developing in the adolescent.

"Some parts of the brain never develop a barrier system at all, for example, the hypothalamus," which is vitally involved in endocrine function. Not only have many experiments shown that excitotoxins (such as MSG) in the diet cause major endocrine problems but also an experiment giving MSG to pregnant mice has shown similar injuries in the offspring, confirming that glutamate passes across the barrier of the placenta and enters the fetal bloodstream.

Consistently, the animals exposed to MSG were found to be short, grossly obese, and had difficulty with sexual reproduction. One can only wonder if the large number of people having difficulty with obesity in the United States is related to early exposure to food additive excitotoxins since this obesity is one of the most consistent features of the syndrome [MSG exposure]. One characteristic of the obesity induced by excitotoxins is that is doesn't appear to depend on food intake. This could explain why some people cannot diet away their obesity. It is ironic that so many people drink soft drinks sweetened with NutraSweet® when aspartate [in it] can produce the exact same lesions as glutamate, resulting in gross obesity The actual extent of MSG induced obesity in the human population is unknown. . . . [However], humans develop higher levels of blood glutamate following ingestion of MSG than any other species of animal known.

Pregnant mothers are seldom warned about dangers to the fetus from excitotoxins. Due to the pioneering work of John Olney, MD, pure MSG has been removed from baby food. However, the food manufacturers continue to add an "even more dangerous product, hydrolyzed vetable protein, which contains three known excitotoxins and has added MSG."

In regard to the intact blood-brain barrier, there are many conditions during which it "can be temporarily broken down, such as with heat stroke, brain trauma, encephalitis, strokes, hypertension, and even severe hypoglycemia." Also, in the aged the blood-brain barrier has often deteriorated. For example, small strokes that we may not even be aware of can leave "a point of seepage for glutamate and other excitotoxins to by-pass the blood-brain barrier. In this way normally excluded excitotoxins from food can endanger the brain." The excitotoxins glutamate and aspartate are relatively small and can pass through an injured barrier when larger molecules are still excluded.

Neurodegenerative Diseases
Dr. Blaylock explains in detail and with excellent illustrations exactly which areas of the brain are involved in the neurodegenerative diseases: amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease), Parkinson's, and Alzheimer's. All three diseases can develop gradually. "The symptoms of Parkinson's disease do not manifest themselves until over 80 to 90 per cent of the neurons in the involved nuclei (called the substantia nigra) have died. The neurons didn't all suddenly die at the same time, rather they slowly and silently deteriorated over many years. The same is true of Alzheimer's disease. This is why prevention is so important."

At times, all three diseases, ALS, Parkinson's, and Alzheimer's, have developed one after the other in the same patients. For example, in Guam following World War II the natives developed exceedingly high levels of ALS and some of them later developed Parkinson's and Alzheimer's. The cause was in their diet of flour made from the seed of the false sago palm (cycad), which has poisonous constituents. They had eaten this flour for centuries but only after "soaking the sliced seeds in water for several hours. This was repeated several times, each time using fresh water. After the last soaking, a chicken was fed some of the wash water. If it lived, the seed was deemed safe to eat." However, because of famine during the war, cycad flour became a much larger part of their diet. Also, fresh water was scarce so the precautionary measures were often abandoned or at least abbreviated. Adding to the problem, the famine could result in the natives having chronically low blood sugar. As explained above, low energy levels can block the detoxification of neurotoxins. Thus the people would be more vulnerable to the devastating neurodegenerative diseases.

Natives of Guam who immigrated to the United States and were no longer exposed to any of the cycad flour still developed the neurodegenerative diseases years later at ten to fifteen times the American rate. Since these diseases develop very slowly, Dr. Blaylock speculates that the people from Guam were exposed here to the less potent neurotoxins glutamate (from MSG) and aspartate (from NutraSweet®), which finally resulted in sufficient additional neurons dying so that they developed the neurodegenerative diseases that had devastated the natives of Guam at even higher rates.

Another potent toxin related to certain opiates and to certain herbicides can cause immediate Parkinson's disease.

Often, injury to the brain can occur at a distance from the original impingement. For example, the cortex of the brain is far from the nigrostriatal neurons. However, quoting Blaylock:

Glutamate, amphetamines, and other excitotoxins may produce Parkinsonism by overexciting the cortical glutamate cells that connect to the nigrostriatal neurons lying deep in the brain. It is sort of like lightning hitting the power line outside your house and burning up all of the appliances connected to that line. The power line represents the cortical glutamate neurons and the appliances the nigrostriatal system.

Dr. Blaylock is concerned about many situations that can result in low blood sugar with the consequent reduced brain energy level and ability to detoxify excitotoxins. People who are trying to lose weight are likely to be cutting down on calories and at same time consuming excitotoxins in NutraSweet® and in the MSG-containing diet foods. Exercise can also "produce rather profound states of hypoglycemia. . . especially in the untrained."

If one suffers heat exhaustion, the

elevated body core temperature can rise sufficiently to cause (at least based on experimental studies) a temporary breakdown of the blood-brain barrier, which can result in leakage of glutamate and aspartate into the brain itself. Also, such physical stress can cause a prolonged fall in the blood glucose and hence in brain glucose, which results in greater vulnerability of the brain to excitotoxins both occurring naturally within the brain and those supplied by the diet. In addition, during extreme exercise a tremendous number of free radicals are formed within the tissues as a result of increased metabolism. This too will add to the damage.

Dr. Blaylock cites research indicating that Alzheimer's patients may suffer from reactive hypoglycemia. One study "seemed to suggest that diabetes and Alzheimer's disease never coexist in the same patient."

Free Radicals and Calcium
"The final common effect of exposure to large doses of excitotoxic amino acids [is] the release of free radicals within the neurons triggered by the influx of calcium." First, the excitatory amino acids cause the influx of calcium, ordinarily controlled by the "calcium pump," which requires much energy in order to work, as does also the pump that can take care of excess excitotoxins. Therefore, when we overwhelm the protective mechanisms with excitotoxins, too much calcium enters the neuron through special channels in the cell membrane. Then an enzyme "breaks down some of the fatty acids that make up the cell membrane." One of these is arachidonic acid, a long-chain omega-6 fatty acid, essential within the membranes but when released, it is the dangerous precursor of free radicals and an inflammatory prostaglandin. Interestingly, elderly rheumatoid arthritic patients who take anti-inflammatory medications appear to have "the lowest incidence of Alzheimer's disease."

"Magnesium helps keep the calcium channel closed so as to protect the cells. . . . Recent nutritional studies have shown up to seventy-five per cent of adults in the United States have a significant magnesium deficiency. . . . In fact, dietary studies and metabolic balance studies indicate that the amount of magnesium in the American diet has been declining during most of this century."

In regard to the blood-brain barrier, in Alzheimer's disease the vessels have the appearance of "Swiss cheese. . . . Another problem seen in children is exposure to excess lead from the environment, such as old lead paint. We know that lead exposure can easily disrupt the blood-brain barrier. In fact, it is a method commonly used in laboratory experiments."

Avoiding Excitotoxins
In summary, Dr. Blaylock recommends first and foremost that we avoid the dietary excitotoxins so prevalent in prepared foods—the MSG and the aspartame ("NutraSweet®"). He also mentions that the excitotoxin "cysteine can easily penetrate the intact blood-brain barrier and that hydrolyzed vegetable protein contains cysteine. . . . [It is] also being added to some bread dough." We need to concentrate on whole, unprocessed food. Dr. Blaylock gives us:


Additives that always contain MSG:

  • Monosodium Glutamate 
  • 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 Spices

Additives that may contain MSG and/or other excitotoxins:

  • Soy Protein Concentrate 
  • Soy Protein Isolate Whey 
  • Protein Concentrate.

In her review of Dr. Blaylock's book NOHA Honorary Member Beatrice Trum Hunter concludes:

Excitotoxins is a valuable contribution to the understanding of the brain and the need to protect it from assaults that result in various health problems and diseases. It is a book that should be read by all health professionals. The work is understandable for concerned laypersons, too. The extensive reference list will serve as a useful tool for those who are laboring to have toxic substances officially banned, not to be permitted as intentional food additives. As noted by Richard C. Henneberry, PhD, "I consider it ironic that the pharmaceutical industry is investing vast resources in the development of glutamate receptor blockers to protect [the central nervous system] neurons against glutamate neurotoxicity in common neurological disorders, while at the same time, the food industry, with the blessing of the FDA [Food and Drug Administration], continues to add great quantities of glutamate to the food supply."2

1Health Press, P.O. Box 1388, Santa Fe, NM 87504, 1994; 264 pages, hard back, $27.00.
2Hunter, Beatrice Trum, "The Neurotoxicity of Food Additives," Townsend Letter for Doctors, August/September 1994, p. 954.


NOHA Board Member Adrienne Samuels, PhD, has carefully studied the research on "glutamic acid (found in all hydrolyzed protein products), aspartic acid (found in aspartame), and L-cysteine (currently used as a dough conditioner and proposed for use as a color preservative for fresh fruit). . . . There are . . . double-blind studies suggesting that these amino acids are safe. A review of studies relevant to the safety and toxicity of glutamic acid, however, suggest that many of them are flawed."1 For example, "in the case of MSG toxicology studies, the placebo used to test the excitotoxin glutamate is NutraSweet®, which contains the excitotoxin aspartate. It has been clearly shown in a multitude of studies that aspartate produces the identical destructive reactions on the nervous system as MSG. It would seem obvious even to the layman that you would not use a control substance to compare to a known toxin if the control contained the same class of chemical toxin. But that is exactly what is being done."2

1Samuels, Adrienne, "Excitatory Amino Acids in Neurologic Disorders," The New England Journal of Medicine, 331(4): 274-5, July 28, 1994.
2Blaylock, Russel L., Excitoxins: The Taste that Kills, Health Press, P.O. Box 1388, Santa Fe, NM 87504, 1994, p. 200.

Article from NOHA* NEWS, Winter 1995

