What Is MSG?

Monosodium glutamate, or MSG, might be one of the scariest-looking words you see on ingredients lists. Luckily, it's not as unnatural or harmful as its name or reputation might lead you to believe. But what is MSG, and why is it added to food?

Food manufacturers and chefs add MSG to food because it enhances flavors. The somewhat meaty taste it imparts to food is best described by the Japanese term umami, which means "savory" or "deliciousness." MSG doesn't taste like much on its own, achieving maximum umami only when combined with other flavor molecules.

Although it's a common ingredient in a variety of Asian cuisines, MSG is perhaps best known in North America for its once-universal use in restaurant Chinese food.

Many Chinese restaurants removed MSG from their menus, however, when customers started developing headaches, chest pain and other symptoms after meals. These ailments, first described in 1968 as Chinese restaurant syndrome, sparked decades of research into MSG's toxicity.

Today, MSG has since been widely exonerated of causing these and other adverse health effects. The U.S. Food and Drug Administration, the American Medical Association and other health organizations all recognize MSG as safe for long-term consumption, with the caveat that some people may exhibit a sensitivity to it.

For most, MSG has very little effect, in part because it's essentially the same as a substance that the body produces naturally. The amino acid glutamic acid, which accounts for the bulk of MSG, is one of the ten amino acids that human cells make on their own. It is also naturally present in almost every food item, especially those that are high in protein.

MSG is a salt of glutamic acid: similar to table salt, which consists of chlorine and sodium, MSG contains glutamic acid and sodium (hence the "monosodium" in its name). In the acidic environment of the human stomach, MSG reverts to glutamic acid, becoming biologically indistinguishable from the comparatively vast quantity of glutamic acid found in a healthy diet.

Although MSG is unlikely to cause health problems for most people, there are a few groups who should watch their consumption of it. Those who limit their sodium intake should know that it contributes sodium to the diet, albeit less than table salt. People who know they're sensitive to MSG should avoid it, but they should also consider whether some other food product might have caused any adverse reactions they've experienced.

Finally, several conflicting studies have emerged on the subject of whether MSG can cause weight gain ; the jury is still out on its precise effects.

But for those who are not sensitive to MSG, and are looking to exclude an unambiguously bad dietary influence, it might make the most sense to focus on known villains like saturated and trans fats.