Ask the average person if they'd prefer a Chinese restaurant that doesn't cook with MSG, and they'll probably say yes. Ask them what MSG is, and they'll probably give you a blank stare.
Why do we have such a strong belief that MSG—it stands for monosodium glutamate, by the way—is unhealthy? It's not like saturated fat, or sugar, or even sodium, nutrients that the FDA has at one time or another declared as something that should be limited. The FDA considers MSG safe to eat for the general population. So do most food scientists. And it's freaking delicious.
It's not that there's no reason for anyone to ever avoid MSG. But the notion that the average person should steer clear from it is unfounded.
First, let's explain what MSG is. There are five basic tastes, and Westerners have always been fond of developing new shades of sweet, sour, bitter and salty. But we took our sweet time becoming properly acquainted with the fifth taste, umami, which translates from Japanese as "pleasant savory taste." It's the kind of meaty, brothy flavor that can be found in fish sauce, soy sauce, mushrooms, yeasty foods like Vegemite, and to a lesser degree, steak and cheese.
It's not that Americans have never enjoyed the flavor, but we haven't cultivated entire cuisines around it in quite the same way as Asia has (consider the fermented fish sauce-soaked fare of Vietnam and the seaweed-rich cuisine of Japan). In 1908, the Japanese biochemist Kikunae Ikeda isolated monosodium glutamate after a particularly delicious bowl of soup sent him on a quest to unlock the chemical composition of umami, which he eventually did by extracting it from wheat and defatted soybean. MSG is distilled umami—it's a sodium ion and a glutamate ion hitched together—and a century later we can thank Mr. Ikeda for making super savory snacks simpler to synthesize.
And Then There Was Fear.
Hands started wringing in 1968, when the Chinese-American physician Robert Ho Man Kwok wrote to the New England Journal of Medicine to complain of feelings of numbness, tingling, and warmth after eating Chinese Food. He called it Chinese Restaurant Syndrome (CRS) and proposed a possible link with MSG, which led to a flurry of other readers sending in letters about their own experiences with CRS.
Because of public concern, the FDA and the Center for Food Safety and Applied Nutrition commissioned an independent review to find out if MSG could be toxic, and that's where things started getting dicey. Study after study began calling out MSG as not only a cause of CRS, but also fat gain, headaches, and asthma attacks.
"The reason I think there's some confusion is those studies aren't really great quality," says Kamal Patel, director of the independent nutrition research organization Examine.com. "When you do trials putting MSG against a placebo to see if there's any short-term effect, the evidence is actually pretty mixed, and there aren't that many randomized trials on MSG. There have only been two large-ish trials, both of which were funded by the International Glutamate Technical Committee that was headed by Ajinomoto, the biggest producer of MSG. They found that with around 2.5 to 5 grams of MSG, some people have some kind of reaction, whether it's headache, nausea, general feeling of discomfort."
There were plenty of problems, though. The first is that these results weren't reproducible; it was found to be unlikely that the same people would experience the same reaction again. The second is that the gold standard in scientific studies is the randomized controlled trial, of which there have been few. The third is that taking that much pure MSG has a very, very different effect from consuming it in a meal.
Taking MSG on its own, or in a very low-calorie broth, can result in glutamate appearing in the bloodstream, which some folks believe links it to the symptoms of Chinese Restaurant Syndrome. But if you eat MSG in food, very little of the glutamate winds up in the bloodstream because of digestion speed and other factors. This is one reason why influential rodent experiments, in which injecting MSG resulted in brain toxicity, don't really hold up.
"Any time you combine it with almost any amount of real food, then the prevalence of side effects goes way down, and there's almost no evidence of any long-term effects," says Patel. "It's actually pretty hard to eat too much MSG, because once you get up to the doses used in trials that cause side effects, often people just get nausea and can't eat any more, or don't want to eat any more or find it unappetizing."
The notion that it worsens asthma symptoms also came from poorly designed, single-arm trials, the results of which weren't replicated in randomized trials, and there's only a hypothetical link to attacks in patients with very severe asthma.
And those rumors that it causes weight gain? "A lot of it has to do with animal studies, and there were some studies where animals were fed MSG and they gained weight," says Trevor Kashey, a nutrition scientist and consultant with a biochemistry background. "But what's not interesting is that it contains calories. So frankly, I'm not surprised that giving animals extra calories gives them extra weight. Honestly, sodium is a nutrient we need to live, glutamate is a nutrient we need to live, but when it's monosodium glutamate, people just flip out."
So It's Totally Harmless?
It's true that there's very little proof that MSG is harmful, but it is a source of sodium. "Both too much and not enough sodium is linked to headaches, brain fog, malaise, neurological issues, kidney issues you name it," Kashey says. "But MSG is one of many sodium sources. Sodium is found in a lot of things that don't even taste salty, like the preservative sodium phosphate. Even a bowl of Corn Flakes has ten percent of the recommended daily intake of sodium."
It's also possible that people with pain syndromes like fibromyalgia, extremely severe asthma, histamine intolerances and certain gut conditions may be more likely to experience side effects. It's not that this has been proven, it's more that there are hypothetical links that could exist. At the end of the day, MSG is just not that well-studied.
"People who feel like they're sensitive shouldn't feel like they're wack jobs," Patel says. "But they also shouldn't feel like they're doing long-term harm to their brains, because effects are most likely a short-term thing, due to glutamate only staying in the blood for one to two hours."
The FDA does require food companies to list MSG as an ingredient and they must list a food's sodium content, but not the precise amount of MSG—so keeping a precise track of your intake is probably impractical. But at the end of the day, if you don't experience a reaction to it, then there's no need to be concerned about insidious, long-term effects.
"On a scale of zero to ten, at zero, there are people who say there's no evidence and ten is people who say it's a neurotoxin," Patel says. "I'd say the level of evidence is around a two."
And most importantly, the dose makes the poison. Ingesting a massive amount in one meal is more likely to cause side effects than having a little bit on a more frequent basis, but as mentioned above, it's very hard to ingest a massive amount of MSG that's close to the amounts that have caused symptoms in randomized trials—the meal would simply be inedible.
The American Chemical Society put it best: "MSG can temporarily affect a select few when consumed in huge quantities on an empty stomach, but it's perfectly safe for the vast majority of people."
More ma po tofu, please.