Q: Do I really need to limit my intake of MSG, or even avoid it altogether?
A: No. Over the past several decades, this common food additive—full name monosodium glutamate—has aroused a lot of fear in the general public, due to anecdotal reports of people experiencing headaches, flushing, rash, and asthma-like symptoms after eating Asian food, which has historically been stereotyped as containing the highest amounts of MSG. In fact, one old term used to describe this phenomenon was “Chinese Restaurant Syndrome,” though more recently it has become known by the less-loaded term “MSG symptom complex.” If you watch Netflix shows, you may have seen this controversy featured in an episode of the original series Ugly Delicious, which described how the MSG symptom complex may be unfairly and racially targeted.
Though it may sound like some industrial additive cooked up in a chemical factory, MSG is actually as natural a flavorant as you can find. It's composed of about 78 percent glutamate (also called glutamic acid) and 12 percent sodium (the rest is water). Glutamate is an amino acid (a building block of protein) that’s found in human cells and many foods—not just Asian foods. A plate of spaghetti with tomato sauce probably has more glutamate than a similar amount of any Asian food.
MSG was first isolated in Japan around 1908, where it was extracted by boiling seaweed. Widely used all over the world, it can also be made from molasses or sugar beets, for example. Many foods, including some of the most flavorful and nutritious ones, are rich in free glutamate (without the sodium molecules). These include walnuts, tomatoes, grape juice, peas, mushrooms, potatoes, chicken, Parmesan cheese, and soy protein. Human milk contains glutamate. A glutamate-free diet would be hard to design.
Nevertheless, many Americans fear MSG—their fear being a source of amazement in such nations as Taiwan and Japan, where people consume large amounts without reporting adverse reactions. Indeed, many large, well-designed studies have failed to find any association between MSG and adverse symptoms of any kind, including asthma and migraines. In an article published in Clinical and Experimental Allergy in 2009, for example, researchers reviewed eight studies looking at the possible relationship between MSG and asthma, rashes, and other allergic problems. They could identify no solid relationship between the additive and those conditions. A paper published in 2016 in The Journal of Headache and Pain looked at six human studies involving MSG as it related to headaches. It found inconsistent evidence to support MSG as a cause of headaches.
Earlier, in 2006, an international symposium of researchers at the University of Heidelberg in Germany reviewed the existing evidence on MSG and concluded that it is harmless in the amounts added to foods, even for pregnant women and fetuses, and that MSG might in fact help some elderly people by improving their appetite. The body processes MSG exactly the same way it processes free glutamate.
Bottom line: It’s possible that a very small percentage of people are sensitive to MSG and feel strange after they eat large amounts of it—but no study has ever been able to show that MSG causes more than transient and mild symptoms, even in people who believe they are sensitive. If you believe MSG gives you headaches or causes other reactions, there is no reason to consume it. Food labels have to list it as an ingredient, and you can find out if a restaurant food contains MSG by asking your server to check with the kitchen. Otherwise, it’s fine to enjoy this savory, palate-pleasing ingredient, keeping in mind that lots of MSG means lots of sodium (it’s a key ingredient in soy sauce, for example, which contains a whopping 900 to 1,000 milligrams of sodium per tablespoon). So if you’re on a sodium-restricted diet, consume it sparingly.
Also see 9 Weird Ingredients in Your Food.