Monosodium glutamate (MSG) has long been a source of controversy, blamed for inducing a number of unpleasant symptoms. But there's no strong evidence to suggest it causes cancer or raises the risk for cancer, and its association with negative side effects is weak.
"There is no link between MSG and cancer," says Ashli Greenwald, RDN, LDN, a dietitian with Johns Hopkins Bayview Medical Center in Baltimore.
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MSG is generally regarded as safe (GRAS), meaning qualified experts have deemed it safe as a food additive when used in amounts reasonable for its intended effect in foods, according to the U.S. Food & Drug Administration (FDA).
What Is MSG?
Characteristically savory, it has been a part of many cuisines worldwide throughout history. Glutamate is found most commonly in meat and fish, sauces and soups, tomatoes, fermented foods, soy sauce, cheeses and mushrooms, according to the Harvard T.H. Chan School of Public Health.
The processed form of glutamate, the additive known as MSG, has been around for more than a century, Greenwald explains. "In 1908, a Japanese professor discovered how to extract glutamate, the sodium salt in MSG, from seaweed broth to use it as a flavor enhancer in other foods," she says.
According to the FDA, the MSG used today is made by fermenting starch, sugar cane, sugar beets or molasses, and the glutamate in the additive is chemically indistinguishable from the glutamate naturally found in food proteins.
You metabolize both forms the same way, and you're likely to get significantly more naturally occurring glutamate than additive MSG, an average of 13 grams and 0.55 grams a day, respectively.
Unpacking MSG's Reputation
In 1968, the term "Chinese restaurant syndrome" was coined by a doctor who described a cluster of transient symptoms after eating Chinese food, according to a May 2016 review in the Journal of Headache and Pain.
After years of receiving reports of such symptoms, the FDA had an independent group of experts look into the safety of MSG. They found MSG to be safe, but acknowledged it can trigger mild, short-term symptoms such as headache, drowsiness, flushing and palpitations in sensitive individuals who get more than 3 grams of the additive without food. (The FDA notes such consumption would be unlikely, given there is less than half a gram of MSG in most foods with added MSG.)
The study authors concluded the association between headache and MSG has not been proven, and that it would be premature to say MSG causes headaches.
"Anecdotally, people do report side effects of MSG," Greenwald says. "But when researchers conduct double-blinded placebo tests, the results are the same whether or not the subjects consumed MSG."
That said, "I do have patients who say they get headaches when they consume MSG," she adds. "If that's the case, I recommend they avoid it." There is no association, however, between MSG and cancer.
If you suspect you are sensitive to MSG, pay careful attention to food labels. Foods containing added MSG are required by the FDA to list it in their ingredients panel.
Foods that contain naturally occurring glutamate — such as soy and yeast extracts, tomatoes and cheese — are not required to list MSG, but they cannot claim to be MSG-free. Thus, it may not be possible to identify all MSG, but this isn't necessarily a problem.
"The amount of naturally occurring MSG in those foods is very small," Greenwald says. "There is no need to avoid them unless you know they are triggers for you." As for ordering food in restaurants, "you can ask for no added MSG," she adds.
- Ashli Greenwald, RDN, LDN, registered dietitian, Johns Hopkins Bayview Medical Center, Baltimore, Maryland
- U.S. Food & Drug Administration: “Generally Recognized as Safe”
- U.S. Food & Drug Administration: “Questions and Answers on Monosodium Glutamate (MSG)”
- Harvard T.H. Chan School of Public Health: “Mushrooms”
- Journal of Headache and Pain: “Does Monosodium Glutamate Really Cause Headache? A Systematic Review of Human Studies”