What is MSG, and is it actually bad for you? - Sarah E. Tracy

In 1968, Dr. Robert Ho Man Kwok felt ill after dinner at a Chinese restaurant. He wrote a letter detailing his symptoms to a prestigious medical journal, pondering whether his illness had resulted from eating monosodium glutamate—also known as MSG. Kwok’s connection between his headache and this common seasoning in American Chinese cuisine was just a hunch. But his letter would dramatically change the world's relationship with MSG, inspiring international panic, biased science, and sensationalist journalism for the next 40 years.

So what is this mysterious seasoning? Where does it come from, and is it actually bad for you? MSG is a mixture of two common substances: sodium, which is well-established as an essential part of our diet, and glutamate, a very common amino acid found in numerous plant and animal proteins. Glutamate plays a key role in our digestion, muscle function, and immune system. Around the time of Dr. Kwok's letter, it had been identified as an important part of our brain chemistry. Our body produces enough glutamate for all these processes, but the molecule is also present in our diet. You can taste its signature savory flavor in foods like mushrooms, cheese, tomatoes, and broth.

Chasing this rich flavor is what led to MSG’s invention in 1908. A Japanese chemist named Dr. Ikeda Kikunae was trying to isolate the molecule responsible for a unique flavor he called “umami,” meaning “a pleasant, savory taste.” Today, umami is recognized as one of the five basic tastes in food science. Each basic taste is produced by unique molecular mechanisms that can’t be replicated by combining other known tastes. In the case of umami, those mechanisms arise when we cook or ferment certain foods, breaking down their proteins and releasing amino acids like glutamate.

But Ikeda found a savory shortcut to producing this chemical reaction. By isolating high quantities of glutamate from a bowl of noodle broth and combining them with another flavor enhancer like sodium, he created a seasoning that instantly increased the umami of any dish. The result was a major success. By the 1930s, MSG was a kitchen staple across most of Asia; and by the mid-20th century, it could be found in commercial food production worldwide.

So when Dr. Kwok's letter was published, the outrage was immediate. Researchers and citizens demanded a scientific enquiry into the popular additive. On one hand, this wasn’t unreasonable. The substance hadn't been tested for toxicity, and its health impacts were largely unknown. However, it’s likely many people weren’t responding to a lack of food safety regulation, but rather the letter’s title: “Chinese Restaurant Syndrome.”

While MSG was commonly used in numerous cuisines, many Americans had longstanding prejudices against Asian eating customs, labeling them as exotic or dangerous. These stigmas fueled racially biased journalism and spread fear that eating at Chinese restaurants could make you sick. This prejudiced reporting extended to numerous studies about MSG and umami, the results of which were much less conclusive than the headlines suggested.

For example, when a 1969 study found that injecting mice with MSG caused severe damage to their retina and brain, some news outlets jumped to proclaim that eating MSG could cause brain damage. Similarly, while some studies reported that excess glutamate could lead to problems like Alzheimer’s, these conditions were later found to be caused by internal glutamate imbalances, unrelated to the MSG we eat. These headlines weren't just a product of prejudiced reporters. Throughout the late 60s and early 70s, many doctors also considered “Chinese Restaurant Syndrome” to be a legitimate ailment.

Fortunately, today’s MSG researchers no longer see the additive in this discriminatory way. Recent studies have established the vital role glutamate plays in our metabolism, and some researchers even think MSG is a healthier alternative to added fat and sodium. Others are investigating whether regular consumption of MSG could be linked to obesity, and it is possible that binging MSG produces headaches, chest pains, or heart palpitations for some people.

But for most diners, a moderate amount of this savory seasoning seems like a safe way to make life a little tastier.