The Mysterious Seasoning: MSG

What is MSG?

Monosodium glutamate (MSG), also known as Ajinomoto or China salt is used as a flavour enhancer in several savoury dishes and is a mixture of two common substances, Sodium and Glutamate. It is known as E621, Monosodium L-Glutamate, Monohydrate (food additive) in the food industry (FSSAI, 2011). Sodium is well documented as an integral part of our diet, as it maintains the fluid balance in the body and is required for the proper functioning of nerves and muscles. Glutamate is the most abundant amino acid present in many plants and animal proteins. It is one of the twenty amino acids used to synthesize proteins in the human body and plays an essential part in body metabolism. Like other amino acids, Glutamate is a fundamental building block for proteins and the abundant excitatory neurotransmitter produced by the brain. The body produces enough Glutamate from various metabolic processes (Zanfirescu et al., 2019). However, this amino acid can also be procured from foods. The distinctive savoury flavour in foods like mushrooms, cheese, tomatoes, nuts, legumes and broth is due to Glutamate.

Origin of MSG

Purified MSG was not synthesized until 1908 when Japanese chemist Kikunae Ikeda tried to isolate the Glutamate responsible for the irresistible flavour. He called it “umami,” meaning “a pleasant, savoury taste.” Today, umami is acknowledged as one of the five basic tastes (sweet, bitter, sour, salty and umami) (Stańska & Krzeski, 2016). The umami flavour arises while cooking or fermenting certain foods, breaking down their proteins and releasing amino acids such as Glutamate. The Japanese scientist isolated high quantities of crystalline salt of Glutamate from a bowl of noodle broth (containing seaweed) and combined them with another flavour enhancer like sodium-ion, thus created a seasoning that instantly enhanced the umami taste of any dish. He called the crystals Ajinomoto “the essence of taste.” During World War II, the US army used the best available food science to develop nutritionally dense rations with added MSG to make the food palatable.

Sources of Glutamate

Glutamate is attached to other amino acids in a protein or in free form within the food. The free Glutamate is responsible for the irresistible umami flavour. The fermentation, ageing and ripening processes increase the amount of free Glutamate in food. For instance, a fully ripened tomato will have more free Glutamate than a firm pale tomato. Whereas sun-drying the tomatoes also increases the glutamate content four times that of fresh tomatoes. Umami-rich foods have been staples in human diets for centuries. Garum was made in ancient Rome by fermenting fish intestines with salt to make the fish sauce (Smith &Andrew, 1998; Zahn, 1912). Evaporating the Garum yields a thick paste called muria, which is used to flavour meals (Saberi et al., 2011; Muusers & Christianne, 2005). Because of glutamates, Garum, just like the tempeh (fermented soybean product) and soy sauce, is a rich source of umami flavour (Lewicka & Paulina, 2011). Some foods are very high in free Glutamate, namely kombu seaweed, marmite, fish sauce and parmesan cheese. Breast milk is also high in free Glutamate, with its content varying by lactation stage. Breast-fed infants consume more free Glutamate per pound of body weight than adults (Agostoni et al., 2000).

Every day, our body synthesizes roughly 50 grams of Glutamate and stores it in major organs such as the brain, muscles, kidneys and liver (Crust et al., 2018). Humans ingest around 10-20 grams of Glutamate per day, primarily from protein-containing foods like meat, cheese, nuts and legumes or through MSG (IGIS, 2022). MSG is metabolized the same way as Glutamate (found in its natural form).

The sensational MSG

In 1968, Dr. Robert Ho Man Kwok, a senior researcher, sent a report to a prestigious journal about his symptoms after eating dinner at an Asian Chinese restaurant. He had a head ache, the numbness spread outward, general weakness and heart palpitations. He called these symptoms “Chinese Restaurant Syndrome.” He wondered if the symptoms were caused by overeating monosodium (MSG), wine or soy sauce (Kwok, 1968). His letter created a global panic and was in sensation for the next four decades. MSG was never studied for toxicity and its health impacts on humans. While MSG was commonly used globally in numerous cuisines, many people had constant prejudices against Asian foods, deeming them exotic or harmful. This prompted racially-biased journalism and spread the fear of dining at Chinese restaurants. A study found that injecting mice with MSG caused severe damage to their retina and brain (Olney, 1969; Onaolapo et al., 2016). Some researchers proclaimed that excess Glutamate could lead to problems like Alzheimer’s disease (Fuchsberger et al., 2019), dementia (Kouzuki et al., 2019), infertility (Nosseir et al., 2012; (Das & Ghosh, 2011), obesity (Collison et al., 2011) and heart-related disorders (Baky, 2009). These animal studies seemingly confirmed the idea, but these often involved injecting super-concentrated MSG doses either subcutaneously (under the skin) or intravenously (administered into veins), which was a non-scientific approach to determine the effects of MSG on oral dietary intakes.

Few studies have reported that MSG consumption does trigger symptoms like headache, burning sensation and numbness in some individuals (Schaumburg, H.H. et al., 1989; Niaz, K. et al., 2018). Meanwhile, other studies report that these symptoms are typically triggered by consuming three or more grams of MSG (Ralten et al., 1995). However, when MSG is added to an average food serving, it is typically less than 0.5 grams (FDA, 2012). The Food and Drug Administration (FDA) considers MSG an additive generally recognized as safe (GRAS) (Zanfirescu et al., 2019). However, it strictly states that if the food contains naturally occurring MSG, the food manufacturers cannot label it with “No added MSG” and the foods containing MSG as an additive must be mentioned in their ingredient list. As per the Codex Alimentarius, the addition of MSG in the food products should be as per the GMP (Good Manufacturing Practice) only in specific categories of food (Codex Alimentarius, 2019). Food Safety and Standards Authority of India (FSSAI) directed that every food containing MSG shall mention the declaration “CONTAINS MONOSODIUM GLUTAMATE NOT RECOMMENDED FOR INFANTS BELOW-12 MONTHS” (FSSAI, 2011).

MSG is found in several processed foods such as canned soups, savoury snacks, noodles, processed meats, spices, broths and flavourings. Therefore, many food companies stopped declaring MSG on the ingredient lists and started using substances that naturally contain it, such as hydrolyzed vegetable protein, hydrolyzed plant protein, plant protein extract, calcium caseinate, sodium caseinate, textured protein, yeast extract or autolyzed yeast. Many times using the word “natural flavouring” allows the use of MSG without stating it on the label.

Today, investigation on the potential health benefits of MSG is ongoing. Research suggests it can help increase salivation and appetite in the elderly (Kochetkov et al., 1992), increase satiety, reduce caloric intake and help impart flavour, while reducing overall dietary sodium (Yamamoto et al., 2009; Wallace et al., 2019). Consistent overconsumption of sodium can increase sodium blood pressure and lead to hypertension. It is now being added as a salt substitute in several processed foods in the USA (Wallace et al., 2019). Researchers discovered that it has an anti-obesity impact, while some research indicated that it could cause overeating, resulting in weight gain. (Stańska & Krzeski, 2016; Zanfirescu et al., 2019).

There are speculations that MSG may induce migraines. However, dietary Glutamate is completely used throughout its transit through the digestive tract. Based on human physiology and evidence in recent scientific studies, the international classification of headache disorders removed MSG from its list of headache triggers in 2018 (IGIS, 2022). MSG was also deemed safe by Regulatory Authorities in the United Nations Food and Agriculture Organization (UN FAO), the World Health Organization (WHO) and the US FDA (Zanfirescu et al., 2019).

Conclusion

Glutamate occurs abundantly in nature and is responsible for imparting umami flavour. Current pieces of evidence and healthcare authorities consider MSG safe. However, rigorous and concrete research such as Randomized Control Trials (RCTs) is needed to establish safety. Reading processed food labels is the best practice for identifying food containing MSG or its substitute.

References:

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About the Author:
Bhavya Pande
Ph.D. Scholar, Dept of Foods and Nutrition,
Faculty of Family and Community Sciences,
The Maharaja Sayajirao University of Baroda, Gujarat.
Email ID: bhavyapande@ymail.com