Monosodium glutamate, or MSG, is a glutamate, or salt of glutamic acid, which is an amino acid (the building blocks of protein). In humans, glutamic acid is a “non-essential” amino acid, which means it is produced by the body, and thus not required in our diet. The human body produces about 40 grams of glutamic acid a day. It is also abundantly found in animals and plants, and thus is often ingested through fruits, vegetables, fish, meat and dairy products.
According to the US Food and Drug Administration, MSG is a naturally occurring salt in tomatoes, Parmesan cheese, potatoes, mushrooms, soybeans and seaweed.
It all started with a broth
In 1908, Kikunae Ikeda, a Japanese professor, studied why dashi, a broth of the seaweed kombu, was so uniquely savoury, and thus extremely popular in his country. He extracted glutamate from kombu and determined that it was the ingredient that gave the soup its taste.
He then studied the properties of different varieties of glutamate: calcium glutamate, potassium glutamate, ammonium glutamate, magnesium glutamate and sodium glutamate. All these salts elicited the same unique savoury taste, but among them, sodium glutamate was the most soluble and the easiest to crystallise.
So he starting extracting glutamate from kombu and attached one (mono) atom of sodium to it. He called his product “monosodium glutamate” and said it exhibited a taste called “umami” — which means “pleasant and savoury”.
Umami is classified as the fifth basic flavour that the human palate can detect, besides sweet, salty, tasty and bitter. Ikeda filed a patent to produce MSG as an additive to enhance flavours of other foods and began to market it as a table condiment called Ajinomoto (“essence of taste”) in 1909.
Today, instead of extracting and crystallising MSG from seaweed broth or other natural foods, MSG is produced by fermentation of starch, sugar beets, sugar cane or molasses in laboratories. Carbohydrates from crops such as corn, sugar beets/cane or cassava are fermented to produce glutamate, which is purified and crystallised before drying. The finished product is a pure, white crystal which dissolves easily and blends well in many recipes.
It is then added to prepared and processed foods such as frozen foods, spice mixes, canned and dry soups, salad dressings and meat or fish-based products. In some countries, it is used as a table-top seasoning. It is a common additive used by restaurants serving East Asian cuisine.
Science of a salt
While MSG has “umami” flavour, it also enhances other flavours already present in the food. In its pure form, MSG is a white crystalline powder; when dissolved in water, it rapidly dissociates into sodium and glutamate ions. MSG stimulates specific glutamate 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 “umami” taste.
The glutamate in MSG is chemically indistinguishable from glutamate present in food proteins. Our bodies ultimately metabolise both sources of glutamate in the same way. According to the FDA, an average adult consumes approximately 13 grams of glutamate each day from the protein in food, while intake of added MSG is estimated at around 0.55 grams per day.
MSG is a neurotransmitter — transporting messages from one nerve cell to another. Because it is said to enhance flavours, some scientists believe it “excites nerve endings” and exhibits “neuro-excitatory properties”, that is the ability to stimulate neurons. In the few cases of excessive stimulation, this can result in killing or damaging of nerve cells. Which is why some people consider MSG to induce headaches at best and Alzheimers at worst.
Safe? The jury’s out
The FDA considers addition of MSG to foods to be “generally recognised as safe”. And yet, when MSG is added in foods, the FDA insists it be listed on the label. This is because over the years, specially since the 1960s, FDA has received many complaints of adverse reactions to foods containing MSG. These reactions — known as MSG Symptom Complex, or Chinese Restaurant Syndrome — include headaches, flushing, sweating, facial pressure or tightness, numbness, tingling or burning in the face/neck, heart palpitations, chest pain, nausea and weakness.
In the 1990s, the FDA asked independent scientific group Federation of American Societies for Experimental Biology (FASEB) to examine the safety of MSG. The report concluded that MSG is safe. The FASEB identified some transient and mild symptoms, such as headache, numbness, flushing, tingling, palpitations, and drowsiness that may occur in some sensitive individuals who consume 3 grams or more of MSG without food. “However, a typical serving of a food with added MSG contains less than 0.5 grams of MSG. Consuming more than 3 grams of MSG without food at one time is unlikely,” says the FDA website.