There are a growing number of clinicians and basic scientists who are convinced that a group of compounds called excitotoxins play a critical role in the development of several neurological disorders including migraines, seizures, infections, abnormal neural development, certain endocrine disorders, neuropsychiatric disorders, learning disorders in children, AIDS dementia, episodic violence, lyme borreliosis, hepatic encephalopathy, specific types of obesity, and especially the neurodegenerative diseases, such as ALS, Parkinson's disease, Alzheimer's disease, Huntington's disease, and olivopontocerebellar degeneration.
Excitotoxins are amino acids such as glutamate and monosodium glutamate, also known as MSG. Glutamate is an endogenous chemical that is essential in forming short term memories in the hippocampus and relaying information from the cortex to the basal ganglia. However an excess of glutamate can overstimulate the receiving neuron, causing the cell to die. Since neurogenesis slows to insignificance in older adults, dead neurons are not replaced and eventually the brain's circuitry starts to decay.
Many foodstuffs contain additives that contain exitotoxins. A representative (but not definitive) list:
hydrolyzed vegetable protein
textured protein
hydrolyzed plant protein
soy protein extract
caseinate
yeast extract
aspartame
It is believed that Vitamin C and Vitamin E both reduce the risk of excitotoxicity by reducing the action of free radicals. However studies of Alzheimer's Disease indicate these vitamins are only beneficial if obtained from natural sources, such as fruits and vegetables. Vitamin pills, multivitamins and dietary supplements seem to have little effect on the accumulation of excitotoxins.