Glutamic acid, or glutamate, is a form of the non-essential amino acid L-glutamine. Glutamate is found in food both free as a single molecule or linked into a protein. Salts of free glutamic acid, such as monosodium glutamate or MSG, are commonly used as food additives. Glutamate is also the most abundant neurotransmitter in the brain and an important component of enzymes and proteins. Though health concerns have been raised about glutamic acid intake, none have been verified by scientific research and amounts found in food are considered safe by the U.S. Food and Drug Administration.
About Glutamate
Amino acids are the building blocks of protein and are also used to synthesize biological signaling molecules such as neurotransmitters in the brain. The tongue senses free glutamate as the taste of umami, or savoriness, thus the use of glutamates as a food additive.. Free glutamate is found naturally in many foods including fish, shellfish, meats, vegetables and especially in fermented or aged foods as well as human breast milk.
Uses
Salts of glutamates are commonly used as a food additive and flavor enhanced in many processed foods. Unpleasant alone, glutamates are able to enhance the sensation of other tastes. Chinese and other Asian restaurants in the U.S. commonly use MSG or other glutamates to economically add flavor to dishes. Glutamic acid is also used to enhance crop growth.
Glutamate and the Brain
Most cells in the brain have receptors for glutamate that cause them to generate an electrical signal, allowing cells in the brain to communicate. If released in large amounts in the brain, glutamate is an excitotoxin, killing brain cells by causing them to generate too much electrical activity. For this reason, glutamate levels in the brain are tightly regulated by cells in the brain and the blood-brain barrier, a special lining of blood vessels in the brain controlling how molecules can move back and forth. Intake of glutamate salts is unlikely to change the levels of free glutamate in the brain.
Safety
Despite concerns, the U.S. FDA currently regards glutamate salts as generally recognized as safe when consumed in the amounts found in foods. Some individuals experience Chinese Restaurant Syndrome or perceived sensitivity to MSG. This may manifest as flushing, tingling, numbness, tightness, headache as well as minor changes in perception or heartbeat. According to a 2000 review in the "Journal of Nutrition," people subjective sensitive to MSG did reports reactions when given MSG, although these reactions were not consistent or reproducible and were not present when MSG is taken with food.
References
- MayoClinic.com: Monosodium Glutamate (MSG): Is it Harmful?; K. Zeratsky RD LD; January 9, 2010
- FDA.gov: Database of Select Committee on GRAS Substances (SCOGS) Reviews: L-Glutamic Acid
- "American Journal of Clinical Nutrition"; The Blood-brain Barrier and Glutamate; R.A. Hawkins; 2009
- "Journal of the American College of Nutrition"; Free Amino Acid Content in Standard Infant Formulas: Comparison with Human Milk; Angostoni et al.; 2000
- "Journal of Nutrition"; Umami and Food Palatability; Yamaguchi and Ninomiyal 2000
- "Journal of Nutrition"; Review of Alleged Reaction to Monosodium Glutamate and Outcome of a Multicenter Double-blind Placebo-Controlled Study; Geha et al.; 2000
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