Monosodium glutamate (MSG) is a common flavor additive that has a reputation for being harmful to your health. While some people may be more sensitive to MSG than others, experts generally consider it safe, especially in smaller doses.
Monosodium Glutamate (MSG) is a flavor enhancer that has been widely used for roughly 100 years.
In addition to being naturally present in certain foods, it’s a common food additive in Chinese recipes, canned vegetables and soups, and other processed goods.
For years, MSG has been viewed as an unhealthy ingredient. However, newer research questions the accuracy of its purported adverse effects on human health.
This article examines MSG and what current evidence has to say about its health effects.
What is MSG?
MSG is short for monosodium glutamate.
It’s a flavor enhancer derived from L-glutamic acid, which is naturally present in many foods. L-glutamic acid is a nonessential amino acid, meaning that your body can produce it by itself and doesn’t need to get it from food.
MSG is a white, odorless, crystalline powder commonly used as a food additive. In the food industry, it’s known as E621. It dissolves easily in water, separating into sodium and free glutamate.
It’s made by fermenting carb sources like sugar beet, sugar cane, and molasses.
There’s no chemical difference between the glutamic acid found naturally in some foods and that found in MSG. This means your body can’t differentiate between the two types.
MSG has a specific taste known as umami — the fifth basic taste alongside sweet, sour, salty, and bitter. Umami has a meaty flavor that refers to the presence of proteins in food.
Besides MSG, other umami compounds include inosine 5’-monophosphate (IMP) and guanosine 5’-monophosphate (GMP).
MSG is popular in Asian cooking and used in various processed foods in the West. It’s estimated that people’s average daily intake is 0.3–1.0 gramsTrusted Source.
Why do people think it’s harmful?
MSG got its bad reputation in the 1960s when Chinese-American doctor Robert Ho Man Kwok wrote a letter to the New England Journal of Medicine explaining that he got sick after consuming Chinese food.
He wrote that he believed his symptoms could have resulted from consuming either alcohol, sodium, or MSG. This sparked a host of misinformation about MSG, which was likely related to then-present biases against Chinese immigrants and their cuisine.
The letter led to the designation of Kwok’s symptoms as the “Chinese restaurant syndrome,” which later became the “MSG symptom complex” (MSC).
Older vs. current research on MSG’s health effects
MSG has been linked toTrusted Source obesity, metabolic disorders, brain toxicity, and MSC. Here’s what the current research has to say about these purported downsides.
Effect on Energy Intake:
Older animal and human studiesTrusted Source state that by making food taste better, MSG disrupts the signaling effect of the hormone leptin in your brain. Leptin is in charge of telling your body that you’ve had enough to eat. In turn, this is said to increase your calorie intake.
However, the current data on MSG’s effects on energy intake is contradictory. Some animal studiesTrusted Source have found that it may reduce appetite, while othersTrusted Source support the idea that its flavor-enhancing properties could lead to overeating.
The contradictory results might have to do with the nutritional profile of a meal. For example, eating MSG-enhanced, high protein meals has been linked in animal studiesTrusted Source to increased feelings of fullness, while this link hasn’t been observed with high carb meals.
However, this could also be because protein is the most filling macronutrient — it might not have anything to do with the MSG content.
Other studiesTrusted Source note that eating MSG-enriched meals could cause you to eat fewer calories at subsequent meals and reduce your energy intake from non-MSG-enriched and savory, high fat foods.
Ultimately, more research on the connection between MSG and energy intake is needed.
Obesity and metabolic disorders:
MSG has been associated with an increased risk of metabolic disorders, primarily due to animal studiesTrusted Source that have linked the additive to insulin resistance, high blood sugar levels, and diabetes.
However, previous research has used imprecise methods for determining MSG consumption, such as injections instead of oral doses. This could lead to effects on the brain that are not associated with dietary intake (1Trusted Source, 2Trusted Source, 12Trusted Source).
What’s more, the current data is contradictory. For instance, animal studiesTrusted Source have found an association between umami substances and anti-obesity effects. In contrast, other animal and human studiesTrusted Source show no effect on body weight.
While it appears that typical dietary MSG intakes are unlikely to influence body weight or fat metabolism, more human studies are needed.
Effect on brain health:
Glutamate plays many important roles in brain function. For starters, it acts as a neurotransmitter — a chemical substance that stimulates nerve cells to transmit signals.
Some animal and human studiesTrusted Source claim that MSG can lead to brain toxicity by causing excessive glutamate levels in the brain to overstimulate nerve cells, resulting in cell death.
However, dietary glutamate likely has little to no effect on your brain, as almost none of it passes from the gut into the blood or crosses the brain barrier.
Overall, no compelling evidence suggests that MSG alters brain chemistry when consumed in normal amounts.
Some people may be sensitive:
Some people may experience adverse effects from consuming MSG due to a condition called MSG symptom complex (MSC). It’s estimated to affect less than 1%Trusted Source of the general population.
MSC is characterized byTrusted Source symptoms similar to those described by Dr. Kwok in his letter. They include weakness, flushing, dizziness, headache, numbness, muscle tightness, difficulty breathing, and even the loss of consciousness.
The threshold dose that causes short-term and mild symptoms in sensitive people appears to be 3 or more grams Trusted Source of MSG without food.
Keep in mind, though, that a 3-gram dose is a high one. A typical serving of an MSG-enriched food contains less than half a gramTrusted Source of the additive, so consuming 3 grams at one time is highly unlikely.
It’s a good idea to work with a healthcare professional or dietitian to determine the amount of MSG that is appropriate for you.
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