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How do we know that MSG causes
brain damage and neuroendocrine disorders?
Scientists tell us that use of MSG places humans at risk. As early as 1957, Lucas and Newhouse (1) noticed that severe retinal lesions could be produced in suckling mice (and to some extent in adult mice) by a single injection of free glutamic acid. Studies confirming their findings using neonatal rodents (2-5) and adult rabbits (6) followed shortly thereafter, with others being reported from time to time(7-11).
Studies commencing in 1969 demonstrated that treatment with free glutamic acid caused brain lesions, particularly acute neuronal necrosis in several regions of the developing brain of neonatal mice, and acute lesions in the brains of adult mice given 5 to 7 mg/g of free glutamic acid subcutaneously(12).
Research which followed confirmed that free glutamic acid, which is usually given as the sodium salt, monosodium glutamate, induced hypothalamic damage when given to immature animals after either subcutaneous (13-34) or oral(19,25-26,28,35-39) doses.
Today, the toxic effects of glutamic acid on certain brain cells are so well understood that researchers interested in brain function and pharmaceuticals that might block the effects of glutamic acid, often use glutamic acid as an ablative tool to kill selected brain cells.
Studies completed in the 1970s demonstrated that at least 25% of the population react to free glutamic acid in processed food, a substance popularly referred to as MSG(40-43). Today, we recognize that MSG-reactions range from mild and transitory to debilitating and/or life threatening(44).
People who are sensitive to MSG react to glutamic acid only in its free form, and only if it has been created through fermentation or some other manufacturing process. Manufactured free glutamic acid differs from glutamic acid bound in protein in that the latter is L-glutamic acid only(45-47), while the former contains L-glutamic acid, D-glutamic acid (45-46), and pyroglutamic acid, and may also contain carcinogenic mono and dichloro propanols, and/or carcinogenic heterocyclic amines(48-49).
Free glutamic acid ingested as MSG can cross the placenta during pregnancy(50-51), can cross the blood brain barrier in an unregulated manner during development, and can pass through the five circumventricular organs, which are "leaky" at best at any stage of life(52-53). In addition, the blood brain barrier can be compromised by such things as drugs, seizures, stroke, trauma to the head, hypoglycemia, hypertension, extreme physical stress, high fever, and the normal process of aging(54). It is generally accepted that the young are particularly at risk from ingestion of MSG.
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