Monosodium Glutamate, commonly abbreviated as "MSG," is a flavor enhancer that is used in the food industry. MSG has a rather bad reputation and is wildly believed to cause many negative health effects when consumed. Many food companies proudly claim about their products having no MSG. But what is MSG? Is the hate it gets justified?
Monosodium Glutamate is the sodium salt of glutamic acid, a naturally occurring non-essential amino acid, meaning it is an amino acid that can be synthesized in the body. Glutamic acid is found naturally in many protein-containing foods, as well as vegetables like tomatoes. As a flavor enhancer, MSG increases the sapidity of food. MSG produces a flavor that cannot be provided by other foods. It elicits a taste described in Japanese as umami, which is translated to "savory."
A particularly concerning effect that MSG is believed to have regards the brain. Glutamate is the excitatory neurotransmitter in the mammalian central nervous system (CNS) playing an important role in both physiological and pathological processes. It is believed that an excessive amount of glutamate can exhaust these neurotransmitters, causing significant effects in the human brain. There have been studies done to lab animals that seem to prove this, too.
However, the methods of the research should also be paid attention to. One of the first and widely cited researches concerning this issue was done by John Olney, where he found many negative effects of MSG when given to mice. It should, however, be noted that in his research, the MSG was injected subcutaneously with 4 g of MSG for every kg of the mice's weight. This is not equivalent to peroral human consumption of MSG, and the amount the average person consumes is nowhere close to 4 g of MSG for every kg of their weight.
It is not to say that MSG is completely safe and every claim of its negative effects has no basis. There are people with hypersensitivity reactions to MSG and might report immediate reactions upon consuming MSG. The addition could make food taste better and make people consume more food than they should. The amount that is consumed also should not be completely disregarded. However, to merely claim of something with little to no knowledge of the subject at hand should not be something to make a habit out of, especially for us medical students.
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Husarova, V. and Ostatnikova, D., 2013. Monosodium glutamate toxic effects and their implications for human intake: a review. JMED Research, 2013, pp.1-12.
Olney, J.W., 1969. Brain lesions, obesity, and other disturbances in mice treated with monosodium glutamate. Science, 164(3880), pp.719-721.