Consumption of MSG has been linked to itching, hyperactivity, headache , and swelling of the tongue and throat, in what is known as MSG symptom complex. Most studies fail to establish an association between MSG consumption and any physiological symptoms. However, some clinical reports do show a link.
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Many people avoid gluten in their diets. Here, we discuss gluten and its impact on health. We also ask whether gluten sensitivity truly exists. MSG: More than just a food additive. Written by Yella Hewings-Martin, Ph. However, these effects can be minimized by the consumption of garlic, ginger, and turmeric.
Consumption of food rich in vitamins C and E and other antioxidants can also minimize the effect of MSG on human health. Locust bean has been reported to be a good alternative to seasonings containing MSG.
Monosodium glutamate MSG is a sodium salt of glutamic acid. It is usually a white powder. Water ionizes it into free sodium ions and glutamic acid, which is an organic compound consisting of five carbon atoms.
It is an alpha amino acid. MSG has almost same structure with glutamate. Monosodium glutamate has a distinctive taste that falls outside the region of the four classic tastes: sweet, sour, salty, and bitter. Due to this special taste, many food producers use MSG to enhance the flavor of their product [2].
Recently, Chaudhari et al. Three umami substances glutamate, 5-inosinate, and 5-guanylate were found by Japanese scientists, but umami has not been recognized in Europe and America for a long time. In the late s, umami was internationally recognized as the fifth basic taste based on psychophysical, electrophysiological, and biochemical studies.
There is a synergism between glutamate and the 5-nucleotides. Since glutamate and 5-inosinate are contained in various foods, umami tasted is induced by the synergism in daily eating [4]. The safety and toxicity of MSG had become controversial in the last few years because of reports of adverse reactions in people who have eaten foods that contain MSG. Many studies had confirmed the adverse reactions of MSG [1,5,6]. MSG has been reported to cause headache, vomiting, diarrhea, irritable bowel syndrome, asthma attacks in asthmatic patients and panic attacks [1].
Obuchi et al. Egbuonu et al. Onyema et al. Meraiyebu et al. The pattern of induction of oxidative stress and alteration of glucose metabolic enzymes in the animals was an indication that oxidative stress induced by MSG in the renal tissues of rats might be contributed by increased tissue glucose concentration resulting from enhanced renal gluconeogenesis [10].
Nwajei et al. The Chinese have used certain seaweeds to enhance the flavor of food for some years. In , the flavor enhancing agent was identified as glutamic acid [1]. Shortly thereafter, methods for extracting glutamic acid from seaweeds were developed [1].
MSG is manufactured through a process of protein hydrolysis, where glutamic acid is freed from protein through enzymatic fermentation or use of chemicals. MSG is also manufactured by a fermentation process in which bacteria are grown aerobically in a liquid nutrient medium. The bacteria release glutamic acid as a by-product of metabolism into the liquid nutrient medium in which they are grown.
The glutamic acid is then separated from the fermentation broth by filtration, concentration, acidification and crystallization and conversion to its sodium salt. About 1.
These bacteria are biotin auxotrophs and biotin vitamin B7 is used as a cofactor. Producers prefer the use of sugars to produce MSG. Some sugar sources used includes, sugarcane, starch hydrolysates gotten from corn or cassava tubers, among others.
Ammonia and ammonium salts are added as Nitrogen source. Vitamins and other nutrients are added to finish off the process. Glutamate accumulation in the medium occurs only under biotin-limiting condition.
The requirements for biotin limitation prevented the use of standard raw materials such as sugar molasses because they contained biotin. Addition of penicillin, or the use of microorganisms auxotrophic for glycerol or oleate, that allows the bacteria to produce large amounts of glutamate without biotin limitation Figure 3.
Monosodium glutamate contains D-glutamic acid, pyroglutamic acid, and various other contaminants in addition to L-glutamic acid [2]. Every amino acid except glycine can occur in two isomeric forms, because of the possibility of forming two different enantiomers around the central carbon atom.
By convention, these are called L- and D- forms, analogous to lefthanded and righthanded configurations. Only L-amino acids are manufactured in the cells and incorporated into proteins. Some D-amino acids are found in the cell walls of bacteria, but not in bacteria proteins. Glutamate has both the D- and L- enantiomers and only the L-glutamate enantiomer has flavor enhancing properties [14].
Manufactured monosodium glutamate contains over Fermented products such as soy sauce steak sauce and Worcestershire sauce have levels of glutamate like foods with added monosodium glutamate. Nonfermented naturally occurring foods have lower relative levels of D-glutamate than fermented products [14] Figure 4.
Unlike other D-amino acids, D-glutamate is not oxidized by the D-amino acid oxidases; therefore, the detoxification pathway is not available for handling D-glutamate. Likewise, D- glutamate when ingested, largely escapes most deamination reactions unlike its L-counterpart. D-glutamate is the most potent natural inhibitor of glutathione synthesis identified to date and this may account for its localization to the liver, since circulating D-glutamate may alter redox stability [14].
Pyroglutamic acid PCA is also known as 5-oxoproline, pidolic acid, or pyroglutamate. It is a common but rarely studied natural amino acid derivative in which free amino group of glutamic acid or glutamine cyclizes to form a lactem. It is a metabolite in the glutathione cycle that is converted to glutamate by 5-oxoprolinase. Pyroglutamate is found in many proteins including bacteriorhodopsin.
N-terminal glutamic acid and glutamine residue can spontaneously cyclize to become pyroglutamate or enzymatically converted by glutaminyl cyclases. Pyroglutamate is a heterocyclic compound and is present in plasma of several species including humans.
However, local brain injections of very high concentrations of pyroglutamate induced neurotoxic lesions that appeared to be like those produced by kianic acid [15] Figure 5. The enzyme-bound phosphorylated glutamate is the intermediate in all three enzymatic reactions. Activated glutamate is transferred to an acceptor molecule, namely cysteine, ammonia and NADPH respectively. Phosphorylated or activated glutamate is highly unstable and prone to spontaneous cyclization into pyroglutamic acid [19].
If the acceptor molecule is not present or unavailable, spontaneous cyclization of activated glutamate leads to pyroglutamic acid generation. Similarly, in methanotrophs, it has been proposed that in stress and nitrogenlimiting conditions pyroglutamic acid is generated from glutamate via glutamine synthetase, as found in in vitro conditions [20]. It is suspected to be carcinogenic in humans. It is primarily created in foods during protein hydrolysis when hydrochloric acid is added at high temperature to speed up the breakdown of proteins into amino acids.
As a byproduct of this process, chloride can react with the glycerol backbone of lipids to produce 3-MCPD. About two-thirds of these samples also contained a second chloropropanol called 1,3-dichloropropane- 2-ol 1,3-DCP which experts advise should not be present at any levels in food.
Food seasoning is a substance that adds flavor to food, for example salt, peppers, and other spices. Spices are vegetable substances of indigenous or exotic origin which are aromatic and have hot piquant tastes, used to enhance the flavor of foods or to add to them the stimulant ingredient contained in them [22].
Seasonings can also be used to replace common salt in a great variety of other industrially prepared food items as well as in the preparation of foods both in restaurants, catering, home kitchen etc.
The ingredient mixture and seasonings when added to various food items change the food composition [23]. There are several brands of food seasonings readily available in the open markets, in-street shops and supermarkets. Reports have indicated that the major active ingredients in flavor enhancers are salt NaCl and monosodium glutamate MSG. The original description of the symptoms having their onset about 20 minutes after the meal included numbness or burning at the back of the neck, radiating into both arms and sometimes into the anterior thorax, which was associated with a feeling of general weakness and palpitation [25].
The symptoms of flushing, dizziness, syncope, and facial pressure were described later [26]. Children can react with fever, convulsion or a steady anxiety.
Monosodium glutamate was widely believed to be associated with CRS. However, reviews of relevant studies have proposed that the studies which associated MSG with CRS did not have the robust experimental design, results were inconsistent and the frequency of responses to MSG intake was not high enough to bring evidence that MSG is the trigger of CRS [27].
This issue remains controversial. Since MSG is identical to glutamate naturally contained in many foods, it is absorbed and metabolized by the body in the same manner. On the other hand, damaging effects have been associated with ingesting MSG, such as those related to Alzheimer and Parkinson diseases. This was dismissed by a consensus conference lead by Nobel Preis laureate Professor Dr. Konrad Beyreuther, because MSG ingested through food cannot cross the blood-brain-barrier in healthy persons [28].
Glutamate is the main constituent of dietary protein and is also consumed in many foods as an additive in the form of monosodium glutamate. Evidence from human and animal studies suggests that glutamate is a major oxidative fuel for the gut and that dietary glutamate is extensively mobilized in the first pass by the intestine [29].
Glutamate is also an important precursor for bioactive molecules, including glutathione, and functions as a key neurotransmitter. Several studies have shown that glutamate is extensively metabolized in the intestine []. Glutamate is the main excitatory neurotransmitter in the body and multiple glutamate receptors and transporters have been found in the gastrointestinal tract and enteric nervous system [32].
It has become apparent that the gut particularly the intestine is also a major site of catabolism of several amino acids, mainly nonessential amino acids glutamine, glutamate, and aspartate [29]. An important distinction to be made, however, although amino acids are catabolized in both liver and gut tissues, the extent to which they are completely oxidized to carbon dioxide varies [29].
Glutamate is a key amino acid linking hepatic amino acid catabolism and gluconeogenesis, because many amino acids are first catabolized to glutamate by transamination [29]. The intestinal metabolism of glutamate is presumed to occur largely in epithelial cells lining the mucosa, enterocytes Figure 8.
Glutamate is an important metabolic link between the tricarboxylic acid TCA cycle and urea cycle involved in cellular energy generation and nitrogen disposal [29] Figure 9. A longstanding concern with dietary glutamate consumption, particularly monosodium glutamate MSG , is the evidence and potential risk of neurotoxicity [29].
Some have raised serious concerns about the potential risk of dietary MSG, parenteral glutamate, and its implications for human diseases, such as obesity [28,31]. However, it is critically important to recognize that the evidence of neurotoxicity in several experimental models only occurred with extremely high enteral and parenteral glutamate loads [15].
Glutamate, like other constituent amino acids ingested in dietary protein, is normally absorbed and metabolized in the small intestine subsequent to proteolytic digestion.
However, some amino acids, especially dietary MSG, are ingested in a free form and thus may be metabolized differently when they are presented to the epithelial mucosa of the stomach [29].
Glutamate receptors are synaptic receptors that are located on the membranes of neuronal cells [33]. They play a central role in excitotoxicity and are implicated in several neurological diseases. According to the review above, there is not enough solid evidence to confirm that a hypersensitivity to MSG exists. Despite this, if a person feels that they may have an MSG sensitivity or notices symptoms after eating food containing MSG, they should stop eating it.
Keeping a food diary may also help. Learn about MSG symptom complex here. MSG occurs naturally in food and in the body. Some manufacturers add it to food, such as fast food, to improve flavor. Historically, there have been reports of various adverse reactions to MSG. However, there is not enough evidence to support this.
Studies that have found links between MSG and certain health concerns have used amounts of MSG that a person is unlikely to consume as part of a meal. Maltodextrin is a powder that manufacturers add to many foods to improve their texture, taste, or shelf-life. The FDA consider it safe, but it can…. Monoglycerides are types of fatty acids made from glycerol and one fatty acid chain. They occur naturally in some foods and are added to others to…. This article provides an in-depth description of food allergies, including the signs and symptoms and what to do when a reaction occurs.
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What is MSG? Is MSG safe? Safe levels. Appearance and production. Uses in food. Historic doubts.
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