Many people are familiar with MSG and its ill-effects, but many do not know that this is a synthetic or refined form of a common food component. Proteins are long strings of smaller units, called amino acids. The amino acid glutamic acid is found in many food proteins, including meat, dairy, soy, and even gluten. In it's bound form (as part of a long chain of amino acids) glutamic acid rarely poses a problem, but in it's "free" form (when the protein chain is "broken" and the glutamic acid is freed) it is an excitotoxin that can have serious effects for our health, especially our neurological health.
We have receptors on our tongue to perceive glutamate, and are motivated to seek out this flavor (often called the "umami" flavor). This is so because for most of human history (and that of the animals that we evolved from), we only encountered glutamate in its bound form in meat. Tasting glutamate meant we were eating meat. These receptors ensured that we, as omnivores, would seek out meat for it's dense nutritional value. The consumption of meat in our ancestors' diets was a driving factor behind the evolution of our large brains, and some have argued, is part of what has made us human. It was discovered quite recently that adding free glutamate to low-protein or nutritionally low-quality foods activates this same system and makes the foods enjoyable and sought-after. Vegetarian and vegan foods make heavy use of free glutamate to compensate for the lack of meat, because people eating this way still crave that taste. These additives are a way to trick the brain into wanting to eat these foods. Soy protein products such as tofu and tempeh, other meat substitutes such as TVP (gluten-based meat substitute), foods made from wheat such as breads, soy sauce, protein powders, pea protein, cheese, and nutritional yeast are all sources of large amounts of dietary-free glutamate that are heavily used in vegetarian and vegan foods.
Bound glutamate in meat is freed by the process of aging, curing, or other processing (this is what "hydrolyzing" is all about), but fresh meat is unlikely to be a problem if purchased and cooked at home. Meat in restaurants is often cooked with MSG or "natural" versions of MSG (which do not need to be listed or disclosed), especially chicken and turkey products (I believe this explains why so many children love to eat chicken nuggets). Of course many higher quality restaurants wouldn't dream of using such additives, but it can be hard to tell as a patron who and what to believe. Fast food and chain restaurants are suspect. Gluten, dairy and soy are some of the most common sources of dietary free glutamate in the modern American diet and it is theorized that this is one reason that the gluten-free, casein-free diet is so effective.
Glutamate and GABA balance
This is a clearly explained introduction to the ways that glutamate and GABA work in the nervous system.
Implementing a low free-glutamate diet:
Excitotoxicity: when nourishing foods do harm
"Free glutamate" free diet
This resource explains the different between "free" and "bound" glutamate, and why one is harmful while the other is not. It also discusses the function of glutamate in the nervous system.
MSG and dietary-free glutamate
Glutamate excitotoxicity in autism and neurological health:
Dietary-Free Glutamate: Implications for Research on Fear-Overconsolidation and PTSD
Excitotoxins, neurotoxins, and human neurological disease
(This is a lecture on YouTube given by Dr Russell Blaylock, MD in which he discusses the role of glutamate as a neurotransmitter, and it's role in many diseases. In addition to neurodegenerative disorders, it play a significant role in cancer, glaucoma, problems in the hypothalamus and adrenal glands, and autoimmune diseases. Glutamate is also central to the way in which viruses damage the central nervous system, and a significant suppressor of mitochondrial function. It is also central to the regulation of the immune system in the brain. As far as his dietary recommendations, he is not distinguishing between "free" and "bound" glutamate, which matter, so high protein foods are not intrinsically a problem.)
The Role of Excitotoxins in Autistic Type Behavior by Dr Amy Yasko
Glutamate toxicity in autism
Autism and Glutamate Dysfunction- Avoid the Cause- Race to the Cure
This is a thorough discussion of many of the ways that glutamate is involved in autism.
MSG and Autism
This page covers many different connections between glutamate and autism, including how glutamate blocking drugs are being increasingly used to treat autism.
What's Triggering Your Migraine? The role of glutamate and other food chemicals in migraine pain.
