Is MSG bad for you?

For more than half a century, the savory flavor enhancer monosodium glutamate (MSG) has gotten a bad rap, with people blaming it for a constellation of symptoms, including headache, indigestion, feeling flushed and acid reflux. And Chinese restaurants have faced the brunt of this condemnation. 

But is MSG really bad for you, or is there more to the story?

According to the U.S. Food and Drug Administration, MSG is considered safe and always has been, according to a 1995 safety study the FDA commissioned. MSG is the sodium salt of the amino acid glutamic acid (and, despite its name, there is no gluten in it). The 1995 study reported some instances of mild and short-term symptoms, like headache, flushing or drowsiness, when individuals who are sensitive to MSG consumed a large amount — 3 grams or more — without food. "However, a typical serving of a food with added MSG contains less than 0.5 grams of MSG. Consuming more than 3 grams of MSG without food at one time is unlikely," according to the FDA. 

If the case on MSG was closed decades ago, why are people still avoiding it? The long-held fear around this umami-boosting ingredient is rooted in an old letter, a series of bad studies and media hysteria of the 1960s and beyond. 

In 1968, a Maryland doctor named Robert Ho Man Kwok wrote a letter to the New England Journal of Medicine describing his symptoms — numbness, weakness and heart racing — after eating Northern Chinese food. He called the sensation "Chinese Restaurant Syndrome" and suggested three possible culprits: salt, cooking wine or MSG.

Related: Why does mint make your mouth feel cool?

MSG was isolated and patented by a Japanese chemist named Kikunae Ikeda in the early 1900s. It became a commonplace additive in East Asian cooking through Japanese imperialism. By around 1926, MSG was making its way to the U.S. by two channels: Chinese restaurants and canned foods, like those from Campbell's Soup Company. By the time of Kwok's letter, MSG was a nearly ubiquitous food additive found in all sorts of processed, packaged and restaurant-prepared foods, and was even a household spice.