The role of glutamate neuroexcitotoxicity in autism, as well as its involvement in various neurological disorders and mood disturbances, is becoming increasingly evident. This phenomenon triggers an overload of oxidative stress within the brain, leading to symptoms such as hyperactivity, seizures, and damage to neurons, especially within the hippocampus—a critical region for learning and memory functions.
The consumption of monosodium glutamate (MSG), a prevalent additive in processed foods, has been shown to provoke seizures in laboratory mice when directly administered. Additionally, glyphosate, a common herbicide, when combined with glutamate, exacerbates the detrimental effects on neural health.
Research involving rats has demonstrated that glyphosate can induce neuroexcitotoxic effects in the hippocampus. This damage is linked to heightened levels of glutamate outside cells and the excessive activation of specific glutamate receptors, known as NMDA receptors.
Adopting a diet centered on certified organic whole foods can serve as a preventative measure against glutamate neuroexcitotoxicity. It also minimizes exposure to glyphosate, offering a straightforward health strategy for families. Some families have observed noticeable improvement in symptoms upon transitioning to an organic diet devoid of gluten and casein (found in dairy).
While the efficacy of a gluten-free, casein-free diet in managing autism remains a contentious topic, numerous parents report digestive improvements in their autistic children following the elimination of these components. We suggest that gluten and casein-rich products often contain elevated levels of glutamate.
Understanding Free Glutamate
Investigations into MSG revealed a substantial body of research linking various health issues to glutamate dysfunction. Glutamate is vital as one of the key amino acids involved in protein synthesis and serves as an alternative energy source for mitochondria. Furthermore, it acts as an excitatory neurotransmitter, prompting neuron activation.
Although glutamate is naturally present in many foods, it typically forms part of a peptide chain within proteins, necessitating digestion before absorption. Conversely, MSG represents a solitary, free glutamate molecule, making it more readily absorbed. The distinction between bound and free glutamate is crucial for understanding its metabolic impact.
The notion that such a critical amino acid could become toxic may seem paradoxical. The key lies in glutamate’s regulation within the brain. As a potent excitatory neurotransmitter, its activity and levels must be meticulously controlled. Normally, glutamate is stored inactively within neuronal vesicles, released for neurotransmission, and then swiftly recycled by astrocytes into glutamine—a non-neuroexcitatory compound.
Free glutamate’s rapid absorption from the gut into the bloodstream, and subsequently the brain, can excessively activate glutamate receptors, leading to overexcitation of neurons. This process generates oxidative stress and potential neuronal harm, a condition known as neuroexcitotoxicity.
Glutamate’s role as a neurotransmitter linked to neuroexcitotoxicity extends beyond autism, correlating with several neurological conditions, including Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, and multiple sclerosis, highlighting its broader implications for brain health.
Safety Status Questioned
The United States Food and Drug Administration (FDA) has recognized MSG as a food additive under the category of “generally regarded as safe” (GRAS). Despite this designation, numerous individuals report adverse reactions, collectively referred to as “Chinese Restaurant Syndrome,” a term derived from the common use of MSG in Chinese cuisine to enhance flavors. This reaction is considered more of a food intolerance than an allergy, with symptoms ranging from muscle soreness and heart palpitations to general weakness, headaches, nausea, flushing, tingling sensations, chest discomfort, and drowsiness. Additionally, a connection has been observed between this syndrome and migraines, with those suffering from migraines showing higher glutamate levels in their bloodstream.
The vast majority of consumers are unaware that free glutamate lurks in countless processed food items, making it a daunting task to fully eliminate it from one’s diet. This is due to the various labels under which glutamate masquerades in ingredient lists, such as “hydrolyzed protein,” “hydrolyzed vegetable protein,” “autolyzed plant protein,” “protein isolate,” “soy extracts,” and “yeast extract.”
Glutamate and Glyphosate: A Toxic Duo
The issue of free glutamate in processed foods is compounded by glyphosate, the key ingredient in the widespread herbicide Roundup. Glyphosate, found in numerous foods due to its application on GMO Roundup-Ready crops (like soy, corn, sugar beets, canola, and alfalfa) and as a pre-harvest drying agent on crops such as wheat, barley, oats, legumes, and sugar cane, has been reassured by U.S. regulatory bodies to be virtually non-toxic to humans.
However, emerging studies challenge this assertion, suggesting that glyphosate, especially in combination with a diet rich in free glutamate, could synergistically elevate the risk of glutamate excitotoxicity in the brain, potentially leading to autism. Given that free glutamate is the predominant excitatory neurotransmitter in the vertebrate nervous system and is especially concentrated in the glutamate receptor-rich hippocampus—a critical area for learning and memory—excessive glutamate can be perilous.
A pivotal 2014 study titled “Mechanisms underlying the neurotoxicity induced by glyphosate-based herbicide in immature rat hippocampus: involvement of glutamate excitotoxicity” demonstrated glyphosate’s capacity to render glutamate neurotoxic in the hippocampus of young rats. This study utilized fifteen-day-old rat pups, exposing them to Roundup through their mothers from gestation until day fifteen post-birth, and also directly exposing hippocampal slices from unexposed pups to glyphosate. Findings from both approaches indicated that Roundup heightened calcium uptake in cells by activating NMDA receptors and calcium channels. It was observed that Roundup increased glutamate release into the synapse and impeded astrocytes’ ability to remove glutamate, leading to neuronal damage due to oxidative stress.
Further research by the same team revealed that rats exposed to a glyphosate-based herbicide prenatally exhibited sustained glutamate excitotoxicity into adulthood. By two months old, these rats displayed depressive behaviors. Drugs targeting NMDA receptor suppression have shown promise in depression treatment, highlighting the receptor’s role in mood regulation. The interaction between glutamate and glycine in stimulating NMDA receptors in the hippocampus is critical. Glyphosate not only promotes glutamate accumulation in the synapse but also mimics glycine, binding to the glycine site on NMDA receptors. Normally, magnesium’s binding at the NMDA receptors inhibits activity, but glyphosate’s chelation of magnesium renders it unavailable, thereby facilitating neuroexcitotoxicity through NMDA receptor activation.
Exploring the Link: Gutamate Overload, Autism and Epilepsy
Epilepsy, a prevalent seizure disorder, ranks as the fourth most widespread neurological condition globally. Individuals with autism are significantly more likely to develop epilepsy compared to the general population. A comprehensive study tracking 150 individuals diagnosed with autism revealed a 22% incidence of epilepsy development.
Research indicates that stimulation of NMDA receptors can initiate limbic seizures in laboratory animals. For instance, mice injected with an MSG solution exhibited signs of excessive neural stimulation, such as head nodding and generalized tonic-clonic convulsions, after merely two doses. Furthermore, a study employing microdialysis to sample neuronal extracellular fluid in rats established that glutamate levels surge at the onset of a seizure.
GABA (gamma-aminobutyric acid), a naturally occurring amino acid, serves as an inhibitory neurotransmitter, dampening excitatory stimuli. A 2010 study highlighted a notable imbalance in the glutamate-to-GABA ratio within the frontal lobes of autistic children compared to non-autistic controls, with a higher glutamate and lower GABA presence in autistic individuals. Earlier research also found elevated glutamate levels in the right hippocampus of autistic children.
A 2011 investigation into the serum free amino acid levels in autistic versus non-autistic children identified significant discrepancies in glutamate and glutamine levels, with autistic children exhibiting higher glutamate and lower glutamine concentrations. These findings contributed to the formulation of the “hyperglutamate theory of autism” by Fatemi in 2008, suggesting the potential repurposing of glutamate receptor antagonists for autism treatment.
The Gut Microbiome and Glutamate
The gut microbiome’s influence on glutamate levels is increasingly recognized. Studies comparing the fecal microbiota of autistic children to that of non-autistic controls found an overabundance of certain protein-degrading microbes in autistic individuals, leading to elevated free amino acids, particularly glutamate, due to insufficient microbial degradation.
Manganese: A Crucial Element
The conversion of glutamate to glutamine in the brain is critically dependent on the enzyme glutamine synthetase, which requires manganese as a cofactor. However, glyphosate’s tendency to chelate manganese renders it inaccessible, potentially disrupting this vital process. Research into cows consuming GMO Roundup-Ready feed revealed significantly reduced blood manganese levels, linking glyphosate exposure to autism via its effect on manganese-dependent enzymes.
Maintaining Health In The Face Of Glutamate Excitotoxicity
To mitigate the risks of glutamate excitotoxicity, adopting a certified organic whole foods diet is paramount, particularly focusing on organic sugar and wheat to reduce exposure to free glutamate and glyphosate. Consuming foods rich in magnesium and manganese is also beneficial, as these minerals play key roles in suppressing NMDA receptor activity and converting glutamate to glutamine, respectively.
The Autism Community in Action (TACA) offers resources on managing dietary glutamate, recommending supplements like magnesium, manganese, selenium, vitamin B12, and others to help modulate glutamate levels. Despite the nutritional value of foods high in glutamate, such as soy, bone broth, and fermented products, their consumption should be moderated in a low-glutamate diet, especially when glyphosate exposure and mineral deficiencies are concerns.