Is MSG Harmful? Unveiling the Facts About This Divisive Ingredient

Monosodium glutamate (MSG) is a popular flavor enhancer in various Asian dishes and certain processed foods. However, it also naturally occurs in nutritious foods like mushrooms, eggs, and tomatoes. Despite being a common seasoning, MSG has faced negative attention over claims that it affects metabolism and brain health. Yet, much of the research surrounding these allegations remains contentious and inconclusive. Let's examine the studies to address the question: Is MSG truly harmful to you?

What Is MSG?

“MSG is derived from L-glutamic acid, an amino acid,” says Amy Davis, RD, a registered dietitian at FRESH Communications. L-glutamine, another term for L-glutamic acid, is not classified as an essential amino acid, meaning the body can produce it naturally without needing to obtain it from food sources.

“MSG naturally occurs in a wide range of foods, from chicken to broccoli, but it can also be produced by fermenting specific starches,” explains Davis. Other foods that naturally contain MSG include meats, seafood, eggs, parmesan and cheddar cheeses, mushrooms, tomatoes, grapes, walnuts, corn, potatoes, and fermented products like miso, soy sauce, and fish sauce.

MSG is also available as a white powder in grocery stores, often used to season dishes. It offers a rich, umami taste, delivering a savory, smooth, and almost meaty flavor. Additionally, MSG activates taste receptors, allowing the other flavors in a dish to stand out.

However, the most common place to find MSG in supermarkets is in a variety of packaged foods. Examples include canned soups, frozen meals, processed meats, certain condiments, and snack items. “It is also used in low-sodium seasoning blends because it contains only a third of the sodium of table salt,” Davis adds.

Fast food chains and some Asian cuisines, such as Chinese food, also frequently incorporate this often-debated seasoning. 

The Origins of MSG’s Negative Reputation

“MSG has been a subject of controversy for many years,” says Davis. But what’s the reason behind it?

In the late 1960s, a person named Robert Ho Man Kwok sent a letter to the New England Journal of Medicine detailing a series of strange and unpleasant symptoms he experienced after dining at a Chinese restaurant. In his letter, he mentioned symptoms such as numbness, weakness, and palpitations. Though he wasn’t sure whether these symptoms were caused by alcohol, salt, or MSG consumed before the reactions, assumptions were quickly made that MSG was the culprit. This episode was later dubbed “Chinese restaurant syndrome,” and eventually renamed “MSG symptom complex (MSC).”

The twist in the story? Robert Ho Man Kwok wasn’t a real person, and the letter wasn’t meant to be taken seriously. The name was actually invented by orthopedic surgeon Howard Steel, who wrote the infamous letter as a joke—part of a bet with another doctor in the 1960s to see if he could get published in the New England Journal of Medicine. What began as a harmless bet turned into a long-running, often racially-charged spread of misinformation about MSG being a dangerous substance.

Is MSG Really Harmful to Your Health?

While it’s true that MSG symptom complex (MSC) is a real condition, it only affects a small percentage of people who are highly sensitive to MSG. “This condition is believed to affect roughly 1% of the population,” says Davis. “It’s marked by symptoms like headaches, dizziness, and numbness following MSG consumption.” Additional symptoms of MSC may include nausea, tingling, and facial flushing.

For the majority of people, however, MSG doesn’t pose such a risk. Over the years, MSG has been linked to various health concerns such as metabolic disorders like type 2 diabetes and obesity, neurotoxicity, kidney damage, and reproductive issues. Numerous studies have pointed to these side effects, including this 2015 review, this 2018 review, this 2018 article, another 2018 study, and this 2021 study.

Nevertheless, there’s a significant amount of peer-reviewed research that disputes these claims. For instance, this 2018 review found no negative effects of MSG on brain function, while a 2016 review concluded there was insufficient evidence to link MSG to headaches. A separate 2018 review also found no substantial proof that MSG is neurotoxic. Furthermore, MSG’s use in ultra-processed foods and its ability to enhance flavor (encouraging overconsumption) could be factors contributing to its association with obesity and other metabolic conditions.

At the same time, numerous studies have shown that the evidence connecting MSG to negative health effects is generally weak and not strongly relevant to typical human consumption. Some of these include a 2017 review, a 2019 article, a 2021 review, and a 2022 review. 

In general, the above papers suggest that many of the studies linking MSG to adverse health effects were often:

• Conducted using animal subjects
• Lacked sufficient control groups
• Involved small sample sizes
• Administered MSG in quantities far surpassing typical human intake
• In some instances, subjects were injected with MSG, which doesn't accurately reflect the effects of consuming it orally 

A common conclusion among researchers is that more robust evidence is required to demonstrate any harmful effects of MSG consumption. “Much of the existing research is inconsistent and often involves animals receiving excessive amounts far beyond what humans typically consume,” notes Davis.

Additionally, MSG is classified as generally recognized as safe (GRAS) by both the Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA)—the latter of which is known for its more rigorous safety standards than the FDA.

Moreover, many nutritious foods like a variety of fruits, vegetables, and lean proteins naturally contain MSG and have not been linked to any of the negative health issues historically associated with this seasoning.

Making Informed Food Choices While Considering MSG

With all this knowledge in hand, how should you approach MSG in your daily diet?

“According to the current research, MSG is just as safe as other flavor enhancers, and consuming it in typical amounts should not cause any negative health effects,” Davis explains. (Of course, this excludes individuals who experience MSC symptoms.)

Like any ingredient, whether it’s sugar, sodium, or MSG, the key is moderation. While you don’t need to be cautious about naturally occurring MSG in healthy foods, you should be mindful of the MSG found in ultra-processed foods.

Many heavily processed foods that contain MSG also have high levels of sodium and added sugars, which may contribute to inflammation and conditions like high blood pressure. These foods are also typically low in essential nutrients such as fiber, vitamins, minerals, and plant compounds. Therefore, it’s best to limit their consumption to a few times per week or less.

To identify MSG in packaged foods, check the ingredients list for “monosodium glutamate.” However, MSG can also appear in disguised forms, such as yeast extract, soy extracts, hydrolyzed yeast, autolyzed yeast, protein isolate, and hydrolyzed vegetable protein.

The Conclusion

Ultimately, MSG has been unfairly stigmatized due to racialized myths and inadequate research. While some individuals may be sensitive to it and should steer clear, MSG naturally appears in many healthy foods that should be enjoyed regularly. On the other hand, it’s also present in many processed foods that are best consumed in moderation.