Monosodium glutamate is called Ajinomoto in Japan. Ajinomoto is a company name but that product is now called ajinomoto as they are the first one to find this MSG. Umami the fifth flavour.
San-mi (sourness) , kan-mi (sweetness), en-mi (saltiness), niga-mi (bitterness), and this umami is the fifth one.
The first umami that was found in 1908 was glutamic acid, glutamate from kombu kelp. Glutamate is normally contained in vegetables (kelp, green tea leaf, tomato, broccoli etc), and other umami inosinic acid is contained in animals (such as bonito, mackerel, meat ). Guanylic acid is contained in shiitake mushroom.
So using this fifth flavour in the food, Ajinomoto made a condiment to add more flavour to the food. Ajinomoto monosodium glutamate is a mix of those umami acids. The main element of Ajinomoto monosodium glutamate is glutamic acid, glutamate. They are made from sugarcane. They get fermented just like miso and soy sauce.
Ajinomoto monosodium glutamate itself is not bad for your body, what you have to be careful about is the amount you eat. When you put too much salt in your food, it is too salty, if you put sugar too much, it is too sweet, but with umami, you can't taste if there is too much of it. That is why some people put too much of it and says it causes health problem, but it is same as eating too much salt or sugar. The right amount of Ajinomoto you should add is one pinch.
From the research today, taking normal amount of monosodium glutamate doesn’t cause you any health problems. Ajinomoto is treated as salt and vinegar.