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FOOD ADDITIVES — — DANGEROUS Powerful excitotoxins like MSG and aspartame, found in processed foods, can bypass the blood-brain barrier, injuring the brain and exacerbating existing disease conditions. Part 2 of 2 ne of the MSG industry's chief arguments for the safety of its product is that glutamate in the blood cannot enter the brain because of the blood-brain barrier (BBB)—a system of specialised capillary structures designed to exclude toxic substances from entering the brain. There are several criticisms of its defence. For example, it is known that the brain, even in the adult, has several areas—the circumventricular organs—that normally do not have a barrier system. These include the hypothalamus, the subfornical organ, organum vasculo- sum, area postrema, pineal gland and the subcommissural organ. Of these, the most important is the hypothalamus, since it is the controlling centre for all neuroendocrine reg - ulation, sleep/wake cycles, emotional control, caloric intake regulation, and immune sys- tem and autonomic nervous system regulation. As stated, glutamate is the most important neurotransmitter in the hypothalamus. Therefore, careful regulation of blood levels of glutamate is very important, since high blood concentrations of glutamate would be expected to increase hypothalamic levels as well. One of the earliest and most consistent findings with exposure to MSG is damage to an area of the hypothalamus known as the arcuate nucleus. This small hypothalamic nucleus controls a multitude of neuroendocrine functions and is also intimately connected to several other hypothalamic nuclei. It has also been demonstrated that high concentrations of blood glutamate and aspartate (from foods) can enter the so-called "protected brain" by seeping through the unprotected areas such as the hypothalamus or other circumventricular organs. Another interesting observation is that chronic elevations of blood glutamate can even seep through the normal blood-brain barrier when these high concentrations are main- tained over a long period of time.“ This would be the situation seen when individuals consume, on a daily basis, foods high in the excitotoxins MSG, aspartame and L-cysteine. Most experiments cited by the defenders of MSG safety were conducted to test the effi- ciency of the BBB acutely. In nature, except in the case of metabolic dysfunction (such as with ALS, amyotrophic lateral sclerosis), glutamate and aspartate levels are not normally elevated on a continuous basis. Sustained elevations of these excitotoxins are peculiar to the modern diet (and in the ancient diets of Orientals, but not in as high a concentration). An additional critical factor ignored by the defenders of excitotoxin food safety is the fact that many people in a large population have disorders known to alter the permeability of the blood-brain barrier. Conditions associated with barrier disruption include hyperten- sion, diabetes, mini stroke, major stroke, head trauma, multiple sclerosis, brain infection, brain tumour, collagen-vascular disease (e.g., lupus), AIDS, Alzheimer's disease, as well as the effects of certain drugs, chemotherapy, radiation treatments to the nervous system and natural ageing. There may be many other conditions also associated with barrier dis- ruption that are as yet not known. When the barrier is dysfunctional due to one of these conditions, brain levels of glutamate and aspartate reflect blood levels; that is, foods con- taining high concentrations of these excitotoxins will increase brain concentrations to toxic levels as well. Take, for example, multiple sclerosis (MS). We know that when a person with MS has an exacerbation of symptoms, the blood-brain barrier near the lesions breaks down, leaving the surrounding brain vulnerable to excitotoxin entry from the blood, i.e., from the diet.** However, not only is the adjacent brain vulnerable, but the openings act as points of entry, eventually exposing the entire brain to potentially toxic levels of glutamate. by Russell L. Blaylock, MD © 1999 First published in MEDICAL SENTINEL (vol. 4, no. 6, Nov-Dec 1999) PO Box 13648 Macon, GA 31208-3648, USA Telephone: +1 (912) 757 9873 Website: www.haciendapub.com First published in MEDICAL SENTINEL (vol. 4, no. 6, Nov-Dec 1999) PO Box 13648 Macon, GA 31208-3648, USA Telephone: +1 (912) 757 9873 Website: www.haciendapub.com NEXUS ¢ 41 EXCITOTOXINS AND THE BLOOD-BRAIN BARRIER AUGUST - SEPTEMBER 2000