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What do we really know about MSG’s effect on health?

Monosodium glutamate (MSG) continues to be a controversial food additive used around the world. In this Honest Nutrition feature, we explain the benefits and risks of MSG and dispel popular myths.

MSG, also known as the fifth taste or umami, is the sodium salt of glutamate — an amino acid naturally occurring in many foods and food additives and an important building block of protein in the body.

Glutamate was discovered from kombu seaweed in 1908 by Japanese professor of physical chemistry, Prof. Kikunae Ikeda. He later extracted the amino acid, dissolved it in water, and neutralized it with sodium hydroxide to form MSG.

Glutamate itself is bitter, but MSG has a unique flavor that led Ikeda to coin the term umami, expanding upon four basic tastes: sweet, salty, bitter, and sour.

MSG occurs naturally in various foods, such as carrot, onion, cabbage, potato, egg yolk, cheese, soy sauce, anchovies, and shrimp.

It is also produced through the fermentation of animal-based or plant-based foods, including molasses, sugarcane, sugar beet, beans, mushrooms, and seaweed.

MSG is used as a food additive and flavor enhancer either in the form of pure monosodium salt or from hydrolyzed protein products, such as vegetable protein.

It was widely accepted and used in Asian countries since its discovery but has been received with less skepticism in Western countries only in the second half of the 20th century.

It is commonly added to restaurant foods to enhance their palatability. More recently, it has supplemented processed foods, such as frozen meals, canned tuna, dietary supplements, salad dressing, and infant formula.

In agriculture, it is used in combination with other ingredients and sold as AuxiGro, which is a fertilizer, pesticide, and plant primer whose role is to increase crop yield.

Myth: MSG is high in salt, or sodium

Fact: Sodium is an important nutrient the body needs in small amounts to maintain blood volume and blood pressure. However, experts associate excess intake of sodium with high blood pressure and an increased risk of heart disease.

Unlike regular table salt, which is 40% sodium, MSG contains only 12% sodium, which is one-third the amount in table salt. Researchers have also explored MSG as a viable alternative to salt to reduce sodium intake and improve public health through a reduced risk of hypertension.

Myth: Foods that contain MSG also contain gluten

Fact: Gluten is a protein present in wheat-based foods that is a health concern for people with Celiac disease or gluten sensitivity. About 35% of the gluten protein consists of the amino acid glutamine, which plays a key role in immune health and which the body needs in larger amounts during times of illness.

However, glutamate — the main amino acid in MSG — is found primarily in protein-rich foods and is an important neurotransmitter that fuels the cells in the gut. The body uses it to make other amino acids and does not need it in greater amounts during times of stress or illness.

Myth: If food package labels do not have ‘MSG’ on them, the food is MSG-free

Fact: The Food and Drug Administration (FDA) requires food manufacturers to list added MSG as “monosodium glutamate” in their ingredient panel. Foods without added MSG extract do not have to list this ingredient. However, that does not mean the food is free from MSG.

MSG occurs naturally in many plant and animal foods. If the packaged product includes any of these MSG-containing ingredients, the product may have MSG. The FDA does ensure, however, that products with MSG-containing food ingredients cannot claim to be MSG-free.

Myth: The body is unable to process MSG effectively

Fact: There are numerous glutamate receptors throughout the gut and nervous system. Moreover, the body metabolizes glutamate consumed from natural foods in the same way it metabolizes glutamate from food additives.

A 2013 animal study showed that MSG consumption beneficially increases the body’s sensitivity to glutamate and increases the number of receptors in the gut.

Xenophobia and anti-Chinese sentiments in the United States date back to the 1800s, when there was an influx of Chinese migrant workers to the U.S., who later opened Chinese restaurants.

In the context of this long-lasting systemic racism, when in 1968, Dr. Robert Ho Man Kwok wrote to the New England Journal of Medicine describing symptoms he experienced after dining at Chinese restaurants in the U.S., the press used these concerns as fuel to promote mistrust of East Asian cuisine.

In his letter, Dr. Kwok wrote that he experienced symptoms approximately 20 minutes after the start of a meal, and he attributed these to the use of MSG, specifically in the Chinese dishes he had consumed, although a variety of foods naturally contain MSG.

His symptoms included numbness or burning at the back of the neck that may have radiated into both arms and the chest, as well as general weakness and heart palpitations.

His report was then followed by several case studies that collectively gave rise to the term “Chinese restaurant syndrome.”

A dated survey of 3,222 people notes that less than 2% of the respondents reported unpleasant symptoms potentially associated with MSG.

Furthermore, researchers have since demonstrated that there is no clear and consistent causal relationship between MSG in restaurant foods and the symptoms described above.

The term “Chinese restaurant syndrome” has racist and xenophobic undertones, and while it still features in some sources, such as the Merriam-Webster dictionary, lexicographers acknowledge that it is both misleading and offensive.

Now, if people do describe experiencing reactions that could be due to MSG consumption, experts refer to those by the proper terminology, that is, MSG symptom complex.

Although the FDA classifies MSG as generally recognized as safe, or GRAS, several studies have explored its potential association with a number of health conditions, especially following reports of mild symptoms and sensitivities after consumption.

According to a 2019 review, there is a link between consuming high doses of MSG and an increased heart rate, the risk of heart attack, and a negative impact on liver health, fertility, and tumor formation in the context of MSG-induced obesity in rats.

However, the authors of the review point out that the quantity of MSG used in these animal studies did not reflect reality in terms of human consumption of MSG.

The review concludes:

“Based on a critical analysis of existing literature, we posit that many of the reported negative health effects of MSG have little relevance for chronic human exposure to low doses. In order for preclinical studies to be significant for human dietary intake, they must mimic the real context of exposure to flavor enhancers (adequate species, dosage, route of administration).”

In fruit flies, MSG increased the production of reactive oxygen species, which are byproducts of metabolism that cause disease, and reduced their life span.

A 2017 lab study found that high doses of MSG potentially act like an endocrine disruptor and may play a role in the development of obesity.

Once again, however, the doses of MSG administered in these studies were higher than both the average daily intake of 13 grams (g) of glutamate from natural foods and 0.55 g from MSG food additives per day, and the safe dosage level of 30 milligrams of glutamate per kilogram (kg) of body weight of daily MSG consumption.

For example, in one experiment, rats received 0.5–1.5 g of MSG per kg of body weight, which caused rapid heartbeat.

For an adult weighing 68 kg (150 pounds), this equates to 34–102 g of glutamate per day, which is 2.5–7.5 times greater than the current average daily intake.

It is therefore important to note that one cannot extrapolate the results of these animal- and lab-based studies to humans.

It is unclear how long-term low-dose exposure to MSG from various food sources affects human health. More rigorous research in humans is necessary.

MSG is the salt form of the amino acid glutamate, which occurs naturally in a wide range of protein-rich foods and vegetables, such as shrimp, seaweed, and tomato.

Despite the FDA having approved MSG as a safe food additive, several health controversies surround its culinary application, and this is reflected in the historical use of the contested term “Chinese restaurant syndrome.”

This terminology has its roots in racism and xenophobia. Any symptoms potentially associated with MSG consumption have since been renamed as MSG symptom complex.

The link between MSG use in humans and the onset of conditions such as obesity, heart disease, infertility, or liver disease remains unclear and unproven.