Glutamate is an excitotoxic amino acid, meaning it will kill brain cells when accumulated in quantity in interstitial tissue or elsewhere, or when ingested in quantity. And “quantity” would differ from individual to individual, “in quantity” being more than a healthy human needs for normal body function.
When present in protein or released from protein in a regulated fashion (through routine digestion) glutamate is vital for normal body function. It is the principal neurotransmitter in humans, carrying nerve impulses from glutamate stimuli to glutamate receptors throughout the body.
Glutamate becomes toxic only when present in greater quantity than a healthy human needs for normal body function. Then as an excitotoxic neurotransmitter, it fires repeatedly, damaging targeted glutamate-receptors and/or causing neuronal and non-neuronal death by over exciting those glutamate receptors until their host cells die (1-6).
It is well documented that free glutamate is implicated in kidney and liver disorders, neurodegenerative disease, and more. By 1980, glutamate-associated disorders such as headaches, asthma, diabetes, muscle pain, atrial fibrillation, ischemia, trauma, seizures, stroke, Alzheimer’s disease, amyotrophic lateral sclerosis (ALS), multiple sclerosis, Huntington’s disease, Parkinson’s disease, depression, schizophrenia, obsessive-compulsive disorder (OCD), epilepsy, addiction, attention-deficit/hyperactivity disorder (ADHD), frontotemporal dementia and autism were on the rise, and evidence of the toxic effects of glutamate were generally accepted by the scientific community. A July 4, 2021 search of the National Library of Medicine using PubMed.gov returned 3971 citations for “glutamate-induced.”
The first study to address the possibility that glutamate from outside the body (from eating for example) might cause brain damage followed by obesity and reproductive dysfunction was published in 1969. At the time, researchers were administering glutamate to laboratory animals subcutaneously using Accent brand MSG because it had been observed that MSG was as effective for inflicting brain damage as more expensive pharmaceutical grade L-glutamate (7).
In the decade that followed, research confirmed that glutamate given as monosodium glutamate administered or fed to neonatal animals causes hypothalamic damage, endocrine disruption, and behavior disorders when given to immature animals after either subcutaneous (8-29) or oral (15,21,22,24,30-34) doses.
In the 1980s, researchers focused on identifying and understanding abnormalities associated with free glutamate, often for the purpose of finding drugs that would mitigate glutamate’s adverse effects. Researchers had confirmed that free glutamate was an excitotoxic amino acid which when consumed in controlled quantities is essential to normal body function as a neurotransmitters and building block of protein. But when accumulated in interstitial tissue in quantities greater than needed for normal body function (in excess), free glutamate became excitotoxic, firing repeatedly and killing brain cells.
References
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