A flavouring agent used to enhance the meat flavour of many processed foods containing meat or meat extracts. It is commonly associated with the Chinese Restaurant Syndrome, an array of symptoms associated with eating a Chinese meal in which excess MSG has been used. All objective studies suggest that sensitivity to MSG is extremely rare. MSG is absorbed as glutamic acid, and since this is the most abundant natural amino acid in blood, it is difficult to elevate blood glutamate through ingesting MSG. Some of the reported side-effects of MSG may be due to impurities. Most are psychosomatic. MSG is not permitted in foods manufactured for babies and infants.
For an overview of the chemistry of glutamic acid, see glutamic acid.Monosodium glutamate, sodium glutamate, flavour enhancer 621 EU food additive code: E621. (IUPAC names: 2-aminopentanedioic acid, 2-aminoglutaric acid, 1-aminopropane-1,3-dicarboxylic acid), commonly known as MSG, Ajinomoto or Vetsin, is a sodium salt of glutamic acid. MSG is a food additive, popularly marketed as a "flavour enhancer". when dissolved in water (or saliva) it rapidly dissociates into free sodium and glutamate ions (glutamate is the anionic form of glutamic acid, a naturally occurring amino acid).
Umami
MSG stimulates specific receptors located in taste buds such as the amino acid receptor T1R1/T1R3 or other glutamate receptors like the metabotropic receptors (mGluR4 and mGluR1) which induce the taste known as umami, one of the five basic tastes (the word umami is a loanword from Japanese;
Sources of glutamate
Natural Occurence
Glutamate itself is a widespread amino acid: it is found naturally in human bodies and in protein-containing foods, such as peas, mushrooms, seaweed, tomatoes, fermented soy products, yeast extracts, nuts, legumes, meats and most dairy products.
Other Sources
Hydrolyzed proteins, or protein hydrolysates, are acid- or enzymatically treated proteins from certain foods. Hydrolyzed proteins are used in the same manner as MSG in many foods, such as canned vegetables, soups, and processed meats.
Another source of MSG is fruits, vegetables and nuts that have been sprayed with Auxigro, a growth enhancer that contains 30% glutamic acid.
Discovery
Despite its ubiquity in common food products, the flavour contributions made by glutamate and other amino acids were only scientifically identified early in the twentieth century. He then patented a method of mass-producing a crystalline form of glutamic acid, MSG.
Commercialization
The Ajinomoto (味の素) company was formed to manufacture and market MSG in Japan; MSG is used commercially as a flavour enhancer, and is added as an ingredient to many snack foods, frozen dinners, and instant meals such as the seasoning mixtures for instant noodles.
Scientific review
In 1959, FDA classified MSG as a "generally recognized as safe", or GRAS, substance. This action stemmed from the 1958 Food Additives Amendment to the Federal Food, Drug, and Cosmetic Act, which required premarket approval for new food additives and led FDA to promulgate regulations listing substances, such as MSG, which have a history of safe use or are otherwise GRAS. Since 1970, FDA has sponsored extensive reviews on the safety of MSG, other glutamates and hydrolyzed proteins, as part of an ongoing review of safety data on GRAS substances used in processed foods. In 1980, the committee concluded that MSG was safe at current levels of use but recommended additional evaluation to determine MSG's safety at significantly higher levels of consumption. In 1986, FDA's Advisory Committee on Hypersensitivity to Food Constituents concluded that MSG poses no threat to the general public but that reactions of brief duration might occur in some people. Other reports gave similar findings:
A 1991 report by the European Community's (EC) Scientific Committee for Foods reaffirmed MSG's safety and classified its "acceptable daily intake" as "not specified", the most favorable designation for a food ingredient. Also, the 1987 Joint Expert Committee on Food Additives of the United Nations Food and Agriculture Organization and the World Health Organization have placed MSG in the safest category of food ingredients. Questions then arose on the role glutamate in food plays in these functions and whether or not glutamate in food contributes to certain neurological diseases.In Japan, an alternate, generic name for the compound (as Ajinomoto (味の素) is a registered trademark) is gurutamin san'natoriumu (グルタミン酸ナトリウム) literally meaning "glutamine acid sodium" or "salt of glutamic acid".
Health concerns
Location of Health Issues
Despite popular and frequent discussion of MSG related health concerns in the United States, it is discussed infrequently in Asia, and in Japan, where it was invented, is almost unheard of.
MSG intolerance
There have been numerous studies of allergies and/or sensitivities to MSG, attributed to the free glutamic acid component, which has been blamed for causing a wide variety of physical symptoms such as migraines, nausea, digestive upsets, bad dreams, disturbed sleep, drowsiness, heart palpitations, hair loss, asthma, anaphylactic shock, rapidly increasing diabetes, and many other complaints. The agency asked FASEB to address 18 questions dealing with:
the possible role of MSG in eliciting MSG symptom complex the possible role of dietary glutamates in forming brain lesions and damaging nerve cells in humans underlying conditions that may predispose a person to adverse effects from MSG the amount consumed and other factors that may affect a person's response to MSG the quality of scientific data and previous safety reviews. Among the report's key findings:An unknown percentage of the population may react to MSG and develop MSG symptom complex, a condition characterized by one or more of the following symptoms: burning sensation in the back of the neck, forearms and chest numbness in the back of the neck, radiating to the arms and back tingling, warmth and weakness in the face, temples, upper back, neck and arms facial pressure or tightness chest pain headache nausea rapid heartbeat weak pulse violent dreams bronchospasm (difficulty breathing) in MSG-intolerant people with asthma drowsiness weakness. In otherwise healthy MSG-intolerant people, the MSG symptom complex tends to occur within one hour after eating 3 grams or more of MSG on an empty stomach or without other food. A typical serving of glutamate-treated food contains less than 0.5 grams of MSG. No evidence suggests that dietary MSG or glutamate contributes to Alzheimer's disease, Huntington's chorea, amyotrophic lateral sclerosis, AIDS dementia complex, or any other long-term or chronic diseases.
Obesity
MSG has been used in newborn laboratory mice to induce adult obesity because of the lesions that it provokes in the arcuate nucleus of the hypothalamus.
Excitotoxicity
Glutamic acid is an amino acid commonly found in foods. Because MSG is absorbed very quickly (unlike glutamic acid-containing proteins in foods), it is known that MSG could spike blood plasma levels of glutamate. The debate is complex and has focused on several areas:
Whether the increase in plasma glutamate levels from typical ingestion levels of MSG is enough to cause neurotoxicity in one dose or over time.At a meeting of the Society for Neuroscience, the delegates had a split opinion on the issues related to neurotoxic effects from excitotoxic amino acids found in some additives such as MSG.
Some scientists believe that humans and other primates are not as susceptible to excitotoxins as rodents and therefore there is little concern with glutamic acid from MSG. While they agree that the combined effects of all food-based excitotoxins should be considered , their measurements of the blood plasma levels of glutamic acid after ingestion of monosodium glutamate and aspartame demonstrate that there is not a cause for concern. While they agree that typical use of MSG does not spike glutamic acid to extremely high levels in adults, they are particularly concerned with potential effects in infants and young children and the potential long-term neurodegenerative effects of small-to-moderate spikes on plasma excitotoxin levels.
Ingredient listing
United States
Under current FDA regulations, when MSG is added to a food, it must be identified as "monosodium glutamate" in the label's ingredient list.
While technically MSG is only one of several forms of free glutamate used in foods, consumers frequently use the term MSG to mean all free glutamate. The free glutamic acid component of MSG may also be present in a wide variety of other additives, including hydrolyzed vegetable proteins, hydrolyzed yeast, soy extracts, and "natural flavorings".
For this reason, FDA considers labels such as "No MSG" or "No Added MSG" to be misleading if the food contains ingredients that are sources of free glutamates, such as hydrolyzed protein.
In 1993, FDA proposed adding the phrase "(contains glutamate)" to the common or usual names of certain protein hydrolysates that contain substantial amounts of glutamate. For example, if the proposal were adopted, hydrolyzed soy protein would have to be declared on food labels as "hydrolyzed soy protein (contains glutamate)."
In 1994, FDA received a citizen's petition requesting changes in labeling requirements for foods that contain MSG or related substances. The petition asks for mandatory listing of MSG as an ingredient on labels of manufactured and processed foods that contain manufactured free glutamic acid. It further asks that the amount of free glutamic acid or MSG in such products be stated on the label, along with a warning that MSG may be harmful to certain groups of people.
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