This is not a comprehensive list, simply some information I have found along the way.
Getting a bit vulnerable tonight but wanted to give an example of what physically happens to our son when he consumes free glutamate and/or sources of MSG. This video shows a mild form of the intense “shakes” he was experiencing nearly 40 times a day. While movements like these (hand flapping, wringing of wrists, aka stimming, etc) are typically lumped under the Autism umbrella, they can also independently be diagnosed as Primary or Complex Motor Sterotypies (CMS). Our son was diagnosed with CMS by our pediatric neurologist. As we started to remove sources of free glutamate (gluten, dairy, soy & processed foods) we noticed that his shakes/CMS started to drastically decrease. In fact, we only noticed the movements following the consumption of a high glutamate food or when inflammation/intrinsic glutamate (produced by the body) was high. Some common symptoms that accompanied these movements included rigidity, hyperactivity, anxiety, night wakings, epic tantrums and so on. In our experience these high levels of glutamate (excitatory neurotransmitter) cause for an imbalance in GABA (calming neurotransmitter), resulting in over excitation (excitotoxcity) of the brain, triggering a long list of symptoms (many of which are also Autism symptoms). Though his movements now occur very infrequently (maybe one every 6 months), they are a way we are able to gauge his inflammation and determine when glutamate levels are high.
If you’re interested in learning more about glutamate, click here: https://nourishedblessings.com/what-is-glutamate/
GABA and Glutamate in Children with Primary Complex Motor Stereotypies: A 1H MRS Study at 7T “Complex motor stereotypies (CMS) are rhythmic, repetitive, fixed, purposeful but purposeless movements that stop with distraction. They can occur in otherwise normal healthy children (primary stereotypies), as well in those with autism spectrum disorders (secondary stereotypies). The underlying neurobiological basis for these movements is unknown, but thought to involve cortical-striatal-thalamo-cortical pathways. In order to further clarify potential neurochemical alterations, GABA, glutamate (Glu), glutamine (Gln), N-acetyl aspartate (NAA) and choline (Cho) levels were measured in four frontostriatal regions, using 1H MRS at 7T.” “Within the CMS group, reduced GABA/Cr in the ACC was significantly associated with greater severity of motor stereotypies (r=-0.59, p= 0.021).” “To investigate the neurobiology of CMS, we have successfully performed an MRS study of children at 7T examining GABA and glutamate in multiple brain regions. We have shown significantly lower GABA in the ACC and striatum in patients with CMS compared to healthy controls. These findings are consistent with abnormal function of corticostriatal networks in children with primary CMS.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4792666/
“An excess of glutamate is a primary contributing factor to a wide variety of neurological disorders like autism, ALS, Parkinson’s schizophrenia, migraines, restless leg syndrome, tourettes, pandas, fibromyalgia, multiple sclerosis, Huntington’s chorea, and seizures. As well as atrial fibrillation, insomnia, bedwetting, hyperactivity, OCD, bipolar disorder, anxiety disorders, and STIMS (repetitive self-stimulatory behaviors like rocking, pacing, body spinning, hand-flapping, lining up or spinning toys, echolalia, repeating rote phrases or other repetitive body movements or movement of objects that are commonly seen in autistic children) and an increased risk of stroke.” (http://www.holistichelp.net/blog/how-to-increase-gaba-and-balance-glutamate/)
“Rearing behavior was found to be associated with significant and selective elevations of striatal glutamate (Glu) and aspartate (Asp) concentrations.” “the present findings support a role of the striatal glutamatergic system in the mediation of spontaneous stereotypic behavior and suggest a potential neuronal mechanism by which transition to stereotypy occurs in these mice.” (http://www.sciencedirect.com/science/article/pii/S0091305703003691)
“Headaches, insomnia, anxiety, mood swings, ADHD-like symptoms, problems regulating our appetite, leaky gut, elevated eosinophils, bedwetting, problems focusing eyes, stimming, seizures, schizophrenia, and unfortunately, the list goes on.” (http://peelingbacktheonionlayers.com/excitotoxicity-when-nourishing-foods-do-harm/)
“Increased glutamate produces insomnia, decreased eye contact and may lead to too much acetyl-choline which can lead to bladder contraction and abnormal eye movements called strabismus. And increased glutamate causes an increase in self-stimulatory behavior (stims).” https://chronicdiseaserecovery.wordpress.com/2013/03/13/glutamate-and-gaba-balance/
“Rhythmic Movement Training in Autism- The rhythmic exercises stimulate many of the areas of the brain which are damaged in autism and improve their function. For optimal effect of RMT the gastrointestinal function need to be addressed. Otherwise toxins, peptides and allergens will cross the mucosa and be transported from the bowels and pass the blood brain barrier, causing continued brain damage by inflammatory and toxic reactions of the brain. It happens quite frequently that the child gets over stimulated by rhythmic exercises and reacts with restlessness and hyperactivity. Such reactions may occur also in children with ADD and ADHD. The cause of these reactions is probably an inability of the brainstem to filter stimulation from the tactile, vestibular and proprioceptive senses. Excessive stimulation reaches the brain and activates its GLUTAMATE RECEPTORS. Glutamate is the most widespread transmitter substance in the brain. If there is an inability to convert stimulating glutamate into inhibiting GABA the child will soon become restless and start wriggling and try to get away. Therefore a child with autism should be on a diet free from gluten, casein and preferably soy. This is especially important for children who do rhythmic exercises. Self stimulating Behavior – If the concentration of glutamate rises to toxic levels outside the neurons they start firing uncontrollably causing self stimulating behavior or stims. These are repetitive body movements that stimulate one or several senses in a regulated manner. They include- hand flapping, body spinning or rocking, mechanically lining up or spinning toys, repeating rote phrases, echolalia, i.e. mechanically repeating what others say
perseveration, (repetition of a particular response, such as a word, phrase, or gesture, despite the absence or cessation of a stimulus). Rhythmic exercises improve speech – Almost all children with autism or ASD have more or less obvious difficulties doing simple active rhythmic exercises. Such difficulties are also common in children with ADD, ADHD and late speech development and indicate a damage of the cerebellum. Such damage is especially common in autism and has been confirmed by many research studies. Damage of the cerebellum may prevent speech from developing since speech cannot develop if the speech areas of the left hemisphere don´t get sufficient stimulation from the cerebellum. By stimulating the cerebellum with rhythmic exercises speech development will be promoted. The Purkinje cells of the cerebellum use GABA as a transmitter substance and the rhythmic exercises will in the long run cause more GABA to be produced provided inflammation of the cerebellum and glutamate accumulation can be prevented by an appropriate diet. http://www.blombergrmt.com/autism-and-rhythmic-movement-training/