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 grams.
The flavor-enhancing effects of MSG are due to its umami taste, which induces salivary secretion. In other words, umami flavors make your mouth water, which can improve the taste of food.
Studies show that umami substances can lower the desire for salty foods. Salt is another flavor enhancer.
Some research postulates that replacing some salt with MSG can reduce people’s sodium intake by approximately 3% without sacrificing flavor.
Similarly, MSG may be used as a salt substitute in low sodium products like soups, prepackaged meals, cold meats, and dairy products.
Summary: MSG is derived from L-glutamic acid, an amino acid found in your body and in many foods. It’s a popular food additive used to enhance flavor. It can be used to reduce overall sodium intake when used in place of salt.
Why do people think MSG is 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).
Later on, numerous studies backed MSG’s bad reputation, stating that the additive was highly toxic.
However, current evidence questions the accuracy of previous research for several reasons, including:
- a lack of adequate control groups
- small sample sizes
- methodological flaws
- a lack of dosage accuracy
- the use of extremely high doses that far exceed those consumed in typical diets
- the administration of MSG via routes with little to no relevance to oral dietary intakes, such as injections
Today, health authorities like the Joint FAO/WHO Expert Committee on Food Additives (JECFA), the Food and Drug Administration (FDA), and the European Food Safety Association (EFSA) consider MSG to be generally recognized as safe (GRAS).
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They have also determined an acceptable daily intake (ADI) of 14 mg per pound (30 mg per kilogram) of body weight per day. This is far more than the amount you’d typically ingest following a normal diet.
Summary: While racial biases and older research implied that MSG was a toxic additive, current evidence and health authorities recognize it as safe.
Older vs. current research on MSG’s health effects
MSG has been linked to 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 evidence states 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 studies have found that it may reduce appetite, while others 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 have been linked 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 studies 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.
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Obesity and metabolic disorders
MSG has been associated with an increased risk of metabolic disorders, primarily due to animal studies 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.
What’s more, the current data is contradictory. For instance, newer animal studies have found an association between umami substances and anti-obesity effects. In contrast, other animals and human studies 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 studies 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.
Research shows that once ingested, MSG is completely metabolized in your gut. From there, it either serves as an energy source, is converted to other amino acids, or is used in the production of various bioactive compounds.
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% of the general population.
MSC is characterized by 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 of MSG without food.
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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 gram of the additive, so consuming 3 grams at one time is highly unlikely.
Summary: Current evidence debunks most of the beliefs that consider MSG harmful or dangerous. However, in some cases, research findings are contradictory, and further studies on humans are needed.
Common foods that contain MSG
MSG is naturally present in many different foods, especially those that are high in protein. It’s also added to ingredients and other foods during processing.
Common foods that contain MSG are:
- Animal-based protein: chicken, beef, salmon, mackerel, scallops, crab, shrimp
- Cheese: Parmesan, Emmenthal, cheddar, Roquefort
- Vegetables: tomatoes, onions, cabbage, green peas, spinach, mushrooms, broccoli
- Processed meats: pepperoni, bacon, pastrami, sausages, salami
- Sauces and dressings: soy sauce, ketchup, mustard, mayonnaise, barbecue sauce, salad dressings
- Premade and packaged foods: canned soups, canned tuna, frozen meals, crackers, potato chips, flavored snacks
- Condiments: seasoning blends, rubs
Additionally, fast-food chains like McDonald’s, Chick-fill-A, and KFC use MSG to season menu items like fried chicken, chicken nuggets, and fries.
Summary: MSG is naturally present in many foods, including some cheeses, meats, and vegetables. It’s also added to some processed and fast-food items.
MSG is a flavor-enhancing additive that’s also naturally present in many protein-rich foods, cheeses, and vegetables.
Although it was considered a toxic ingredient during the 1960s, current evidence has dispelled that myth, indicating that MSG is safe when consumed in moderate amounts.
Still, you shouldn’t eat excessively large doses or consume it if you experience adverse reactions.
Try this today: There’s no compelling reason to avoid MSG if you don’t experience side effects when consuming it. That said if you’d like to reduce your intake of added MSG, be sure to check the ingredient panel of packaged foods and condiments. The FDA requires that foods that contain this additive mention it on their packaging.