The Internet is abuzz with chatter about MSG. Perhaps you’ve heard it’s perfectly safe. Or that it causes mild problems for people who have a sensitivity to it. Or even that it’s a toxic chemical that’s slowly killing us all.

To set the record straight, we’ve taken a close look at the large body of scientific research and spoken with the U.S. Food and Drug Administration and Ajinomoto (the original producer of MSG) to learn the essentials about MSG: what it is, why it’s used, and whether or not it’s safe.

What is MSG?

Like its name suggests, monosodium glutamate (MSG) is the product of two smaller components: sodium and glutamate. (Both of which are present in foods we eat every day.) Sodium is part of table salt and glutamate can be found in high concentrations in Parmesan cheese and soy sauce. Glutamate is also naturally abundant in our own bodies and is vital to a wide range of biological functions Metabolic fate and function of dietary glutamate in the gut. Burrin DG, Stoll B. The American Journal of Clinical Nutrition. 2009 Sep;90(3):850S-856S.. Because the human body produces its own glutamate, consuming glutamate in your diet isn’t necessary—though it may be difficult to avoid, since it's a natural component of nearly every food protein.

When sodium (a positively charged molecule) is combined with a negatively charged molecule, the result is called a sodium salt. MSG is the sodium salt of the amino acid glutamate.

Discovery and Production

Why MSG Has a Bad Rap (But Doesn't Deserve It)
MSG was first isolated in 1908 by Japanese scientist Kikunae Ikeda as the compound that gave dashi (a Japanese soup base made from seaweed and fish) its distinct flavor. Ikeda successfully crystallized MSG and described its unique taste as “umami,” which roughly translates to “delicious taste.” In the year following his discovery, Ikeda and his partner founded Ajinomoto and began producing MSG for use in food.

Ajinomoto and other manufacturers produce MSG by fermenting corn, sugar cane, and tapioca. To meet Food Chemical Codex regulations, the glutamate in MSG must be 99 percent pure. This is so pure that the body can't distinguish the manmade glutamate from the kind that naturally occurs in things like meat and cheese, says Dr. Eyassu Abegaz, director of scientific and regulatory affairs at Ajinomoto North America. MSG manufacturers also add sodium to the glutamate because it creates a powder that is easy to store, ship, and use, Abegaz, said.

Note: In the rest of this article the terms glutamate, L-glutamate, glutamic acid, monosodium glutamate, monosodium L-glutamate, and umami will be used interchangeably to describe MSG.

The Fifth Taste

Human tastebuds are primed to distinguish between at least four basic tastes: salty, sour, bitter, and sweet. It’s long been suspected that we also have taste receptors specifically designed to detect umami. In 2000, researchers at the University of Miami School of Medicine finally pinpointed the receptors A metabotropic glutamate receptor variant functions as a taste receptor. Chaudhari N, Landin AM, Roper SD. Nature Neuroscience. 2000 Feb;3(2):113-9.. The researchers found that our mouths have L-glutamate receptors (just like we have sweet and bitter receptors), which allow us to recognize umami whenever free glutamate molecules touch our tongues. This has solidified umami’s classification as the fifth basic taste The discovery of umami. Lindemann B, Ogiwara Y, Ninomiya Y. Chemical Senses. 2002 Nov;27(9):843-4. Gustatory system: the finer points of taste. Trivedi BP. Nature. 2012 Jun 20;486(7403):S2-3..

Although the taste sensation of umami is unique, most people find it vague and difficult to describe because it tends to serve a supporting role when combined with other flavors. Umami, however, is perhaps best described as a meaty, mouth-filling, richly savory taste Taste receptors for umami: the case for multiple receptors. Chaudhari N, Pereira E, Roper SD. The American Journal of Clinical Nutrition. 2009 Sep;90(3):738S-742S.

Scientists have also discovered glutamate receptors in our gut Glutamate. Its applications in food and contribution to health. Jinap S, Hajeb P. Appetite. 2010 Aug;55(1):1-10.. It’s presumed these receptors signal the brain to prepare for the digestion of protein-rich food, which supports the theory of taste as an indicator of nutrition. It goes like this: Humans tend to like sweet tastes because they signal to our body that we’re consuming carbohydrate energy. It may follow that we tend to like umami because it sends a signal to our body that we’re consuming the protein our bodies need The discovery of umami. Lindemann B, Ogiwara Y, Ninomiya Y. Chemical Senses. 2002 Nov;27(9):843-4..

Why Is MSG Added to Food?

MSG is typically added as a flavor enhancer. It tends to enhance salty and savory flavors while muting bitterness and sourness. MSG can also unify and balance the flavors of a dish while causing them to linger longer on the tongue. Because of these properties, MSG is often added to soups, snack foods, and prepared entrees. But it's rarely added in large quantity to any food. In fact, the amount of MSG added to processed foods is similar to the concentration of free glutamate that naturally occurs in tomatoes or Parmesan cheese Glutamate. Its applications in food and contribution to health. Jinap S, Hajeb P. Appetite. 2010 Aug;55(1):1-10..

From a food production standpoint, MSG is a popular additive because it offers an affordable way to enhance the flavor of a wide variety of savory foods. MSG can also be used to reduce the amount of sodium in foods—it contains 30 percent less sodium than table salt, but its flavor-boosting ability keeps low-sodium foods palatable.

Other glutamate-rich seasonings, such as yeast extract and hydrolyzed vegetable protein (HVP), can achieve the effects of umami without using granulated MSG. These ingredients might add notes of cheese, chicken, or beer, depending on the strain of yeast or type of vegetable protein used during production. The choice between using MSG and one of the alternative flavor enhancers is often based on the flavor profile, cost (MSG is often the cheapest option), and labeling—food producers know MSG is unpopular with some consumers, and these alternatives might not trigger the same negative reaction.

Labeling of MSG and Other Flavor Enhancers

Critics of MSG often refer to yeast extracts and HVPs as hidden MSG because these flavor enhancers contain significant levels of MSG, but don’t have to be labeled as such on food packaging. The FDA requires companies to list all the ingredients in a product, but producers don't need to detail the components of a single ingredient. And since the glutamates in yeast extracts and HVPs is a component of the yeast or vegetable protein—no crystallized MSG is added—the glutamate doesn't have to be listed on the label.

The most common exception to this FDA rule is if ingredient is of the “big eight” allergens: milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, and soybeans. In that case, food producers are required by law to mention the ingredient by its common name on the label at least once.

The FDA doesn’t require this kind of labeling for MSG because MSG sensitivity is not an allergy Monosodium glutamate 'allergy': menace or myth? Williams AN, Woessner KM. Clinical and Experimental Allergy: Journal of the British Society for Allergy and Clinical Immunology. 2009 May;39(5):640-6.. The symptoms generally attributed to MSG are mild and temporary, unlike some severe allergic reactions, which can require swift medical attention Executive summary from the report: analysis of adverse reactions to monosodium glutamate (MSG). Federation of American Societies for Experimental Biology. The Journal of Nutrition. 1995 Nov;125(11):2891S-2906S..

Additionally, the FDA classifies MSG as Generally Recognized as Safe (GRAS). Dr. Marianna Naum, a FDA spokesperson, explained the steps to achieve GRAS status: “There must be evidence of expert consensus that its use in food is safe, and the information relied on to establish its safe use must be publicly available.” MSG has been classified as GRAS since the list’s inception in 1958. But MSG’s GRAS status hasn’t saved it from considerable controversy over the years.

Even with the FDA’s general approval of MSG, the organization still strongly discourages false advertising, Dr. Naum said. “Claims such as ‘No MSG’ or ‘No added MSG,’ could potentially be considered false or misleading on foods that contain sources of MSG or substantial amounts of naturally occurring free glutamate,” Dr. Naum said.

Chinese Restaurant Syndrome

Why MSG Has a Bad Rap (But Doesn't Deserve It)
In 1968, Dr. Robert Ho Man Kwok wrote a letter to the New England Journal of Medicine where he described feeling sensations of numbness, tingling, warmth, and tightness after eating Chinese food. Dr. Ho Man Kwok acknowledged there were many potential causes for his symptoms, including MSG sensitivity. He called these symptoms Chinese Restaurant Syndrome, though it is often referred to today as “MSG Symptom Complex.” His letter sparked a flurry of follow-up letters that specifically called out MSG in Chinese food.

Due to growing consumer concern at the time, the FDA and Center for Food Safety and Applied Nutrition commissioned an independent review of all scientific findings on MSG to offer a conclusive answer to the question: Is MSG dangerous?

The Federation of American Societies for Experimental Biology (FASEB) conducted the study and published its findings in 1995 as a supplement to The Journal of Nutrition Executive summary from the report: analysis of adverse reactions to monosodium glutamate (MSG). Federation of American Societies for Experimental Biology.  The Journal of Nutrition. 1995 Nov;125(11):2891S-2906S..

“The FASEB report did identify temporary and generally mild symptoms that may occur in some individuals after consuming 3 grams of MSG without food,” said Dr. Naum, spokesperson at the FDA. “However, to date, scientists have not been able to consistently trigger these temporary reactions in studies where MSG was provided with food.”

Three grams of MSG is more than five times the amount of MSG an average adult consumes in a day. When MSG is consumed with food, even mild Chinese Restaurant Syndrome symptoms become less apparent and repeatable.

FASEB’s findings have been confirmed by more recent MSG research, including a large multicenter, double-blind, placebo-controlled, multiple challenge test. Researchers on this study concluded: “Neither persistent, nor serious effects from MSG ingestion are observed, and the responses were not consistent on retesting” Review of alleged reaction to monosodium glutamate and outcome of a multicenter double-blind placebo-controlled study. Geha RS, Beiser A, Ren C, et al. The Journal of Nutrition. 2000 Apr;130(4S Suppl):1058S-62S..

MSG and Asthma

A decade ago, the phrase Chinese Restaurant Syndrome was coined in a letter to the editor in The New England Journal of Medicine. Another series of letters in the same journal detailed stories of individuals experiencing asthmatic symptoms after eating food with high levels of MSG. A study prompted by these letters found that 13 of the 32 test subjects had asthma attacks after taking pills of MSG Monosodium L-glutamate-induced asthma. Allen DH1, Delohery J, Baker G.  The Journal of Allergy and Clinical Immunology. 1987 Oct;80(4):530-7..

This study was heavily criticized, however, because it gave patients up to five grams of MSG in capsule form, significantly more than the half gram an average person consumes daily. Since the 1980s, studies have repeatedly and consistently shown no link between asthma attacks and eating MSG Monosodium L-glutamate-induced asthma. Allen DH1, Delohery J, Baker G. The Journal of Allergy and Clinical Immunology. 1987 Oct;80(4):530-7. Monosodium glutamate sensitivity in asthma. Woessner KM, Simon RA, Stevenson DD. The Journal of Alergy and Clinical Immunology. 1999 Aug;104(2 Pt 1):305-10. The effects of monosodium glutamate in adults with asthma who perceive themselves to be monosodium glutamate-intolerant. Woods RK, Weiner JM, Thien F, et al. The Journal of Allergy and Clinical Immunology. 1998 Jun;101(6 Pt 1):762-71. Monosodium glutamate and asthma. Stevenson DD. The Journal of Nutrition. 2000 Apr;130(4S Suppl):1067S-73S. Food allergy and asthma--what is the link? Roberts G, Lack G. Pediatric Respiratory Reviews. 2003 Sep;4(3):205-12. Food Intolerance and childhood asthma: what is the link? Beausoleil JL, Fiedler J, Spergel JM. Pediatric Drugs. 2007;9(3):157-63. Effects of oral monosodium glutamate in mouse models of asthma. Yoneda J, Chin K, Torii K, et al.  Food and Chemical Toxicology. 2011 Jan;49(1):299-304..

MSG and Migraines

In recent years, there’s been an increasing number of anecdotes of MSG inducing migraines in people with a sensitivity. Migraines are fundamentally different from the Chinese Restaurant Syndrome symptoms, so determining if MSG causes migraines requires its own research.

A review of MSG research published in Appetite, a peer-reviewed journal, states, “In the absence of clinical data, we cannot make any conclusions about glutamate as a potential trigger for migraine headaches. Therefore, with no consistent data to suggest that glutamate causes any type of headache, much more extensive clinical research would be required to establish a link between glutamate and migraine headaches” Glutamate. Its applications in food and contribution to health. Jinap S, Hajeb P. Appetite. 2010 Aug;55(1):1-10..

Are You Sensitive to MSG?

Why MSG Has a Bad Rap (But Doesn't Deserve It)
In the world of science, causality is a tricky thing to prove. Even if your results do indicate causality, they’re only considered reliable if you have a large number of test subjects, unimpeachable methods, and (this one’s the kicker) the results are repeatable. If another scientist repeats the experiment but gets different results, it suggests that chance (or some other factor) came into play in the initial results. Repeatability has been the main problem for those seeking to establish that MSG is the cause of Chinese Restaurant Syndrome.

The best studies I found on MSG found that any adverse reactions were inconsistent and not repeatable. The lack of scientific evidence behind the claim that MSG triggers Chinese Restaurant Syndrome doesn’t necessarily mean that the syndrome (or something like it) isn’t real—it just means that MSG isn’t causing it in a scientifically measurable way.

If you think you’re sensitive to MSG, here are some possible scenarios as to what's causing your symptoms:

  1. You may be sensitive to some part of the food you eat, but not specifically to MSG.
  2. You may be mildly allergic to something in your food. Mild allergic reactions to the soy or fish common in Chinese food are sometimes misattributed to MSG sensitivity Review of alleged reaction to monosodium glutamate and outcome of a multicenter double-blind placebo-controlled study. Geha RS, Beiser A, Ren C, et al. The Journal of Nutrition. 2000 Apr;130(4S Suppl):1058S-62S..
  3. You may be sensitive to the high histamine levels present in many Chinese foods, which can mimic an allergic reaction Monosodium glutamate 'allergy': menace or myth? Williams AN, Woessner KM. Clinical and Experimental Allergy: Journal of the British Society for Allergy and Clinical Immunology. 2009 May;39(5):640-6. Executive summary from the report: analysis of adverse reactions to monosodium glutamate (MSG). Federation of American Societies for Experimental Biology. The Journal of Nutrition. 1995 Nov;125(11):2891S-2906S. .
  4. You have a pre-existing vitamin B6 deficiency, which some researchers have speculated is the true cause of Chinese Restaurant Syndrome symptoms The biochemistry of vitamin B6 is basic to the cause of the Chinese restaurant syndrome. Folkers K, Shizukuishi S, Willis R. Hoppe-Seyler's Zeitschrift Fuer Physiologische Chemie. 1984 Mar;365(3):405-14. Executive summary from the report: analysis of adverse reactions to monosodium glutamate (MSG). Federation of American Societies for Experimental Biology. The Journal of Nutrition. 1995 Nov;125(11):2891S-2906S..
  5. You may be experiencing pain due to irritation of the esophagus Glutamic acid, twenty years later. Garattini S. The Journal Nutrition. 2000 Apr;130(4S Suppl):901S-9S..
  6. You have a true sensitivity to MSG.

If you’re experiencing symptoms after eating Chinese food or other food containing MSG, your best course of action is to see a doctor, who can then refer you to an allergist, registered dietitian, or other specialist for further testing. A healthcare specialist might recommend that you try an elimination diet, where you systematically avoid certain foods in order to identify the root cause of a symptom.

The Source of MSG's Bad Rap

Most of the research against MSG stems from two sources.

The first: Dr. Russell L. Blaylock’s 1996 book Excitotoxins: The Taste That Kills, which argues that nerve cells in the brain and elsewhere are killed by excessive stimulation of neurotransmitters, including glutamate.

The argument for brain damage originates in a 1969 article about MSG injections in young mice Brain lesions, obesity, and other disturbances in mice treated with monosodium glutamate. Olney JW. Science. 1969 May 9;164(3880):719-21.. The newborn mice were injected with heavy doses of MSG under the skin, which can't be fairly compared to amount and manner in which humans typically consume MSG Review of alleged reaction to monosodium glutamate and outcome of a multicenter double-blind placebo-controlled study. Geha RS, Beiser A, Ren C, et al. The Journal of Nutrition. 2000 Apr;130(4S Suppl):1058S-62S..

Glutamate is an excitotoxin that can cause brain cell death, but that role is actually essential for normal brain function. Every paper I’ve come across on the topic of exicitotoxicy refers to endogenous glutamate (the type made by our bodies), or glutamate that’s been injected or administered in a way that completely circumvents the digestive system. I couldn’t find any papers arguing that dietary MSG has any effect on brain chemistry. In fact, recent studies have found that 95 percent of dietary glutamate is metabolized in the digestive tract and turned into fuel or other amino acids Metabolic fate and function of dietary glutamate in the gut. Burrin DG, Stoll B. The American Journal of Clinical Nutrition. 2009 Sep;90(3):850S-856S. Intestinal glutamate metabolism. Reeds PJ, Burrin DG, Stoll B, et al. The Journal of Nutrition. 2000 Apr;130(4S Suppl):978S-82S.. What little glutamate does make it into the bloodstream is prevented from entering our brains in any significant quantity by the blood brain barrier The blood-brain barrier and glutamate. Hawkins RA. The American Journal of Clinical Nutrition. 2009 Sep;90(3):867S-874S.. Given this information, the idea that the MSG we eat somehow travels to the brain and causes damage is a stretch.

Perhaps the best-researched and written criticism of MSG I could find comes from Adrienne Samuels, a self-proclaimed advocate against MSG who first became interested in the topic after her husband developed symptoms related to consuming MSG.

In her review of MSG research and legislation, she clearly documents the history of the food industry’s influence on research studies, FDA rulings, and suppression of others’ results The toxicity/safety of processed free glutamic acid (MSG): a study in suppression of information. Samuels A. Accountability in Research. 1999;6(4):259-310.. It’s a story we saw when researching nonnutritive sweeteners too. Whenever large corporations have a stake in research, there’s bound to be influence and politics involved.

But, just because the history of MSG is clouded with politics and agendas doesn’t mean it’s unsafe. I think Samuels makes a compelling argument that the industry has more to do with MSG research than we should feel comfortable with, but I don’t think she makes a compelling argument that MSG actually causes harm.

If you come across sites or stories that are anti-MSG, check to see whether the arguments stem from either Dr. Blaylock’s book or Samuels's website, and then see if they take into account other publicly-available published research.

Slow Changing Opinions

So why do people continue to condemn MSG after 40 years of science has failed to show that consuming MSG causes harm? Once fear is ingrained, it’s difficult to completely remove.

Adding to this consumer uncertainty is the fact that the true cause of Chinese Restaurant Syndrome is still a mystery. Many people are left wondering, “Why do some people feel ill after eating food containing MSG?” Some researchers speculate that the symptoms of Chinese Restaurant Syndrome are caused by referred pain due to irritation of the esophagus The Chinese restaurant syndrome: an anecdote revisited. Kenney RA. Food and Chemical Toxicology. 1986 Apr;24(4):351-4.. Others suspect it could involve a Vitamin B6 deficiency or the high histamine levels present in many Chinese foods The biochemistry of vitamin B6 is basic to the cause of the Chinese restaurant syndrome. Folkers K, Shizukuishi S, Willis R. Hoppe-Seyler's Zeitschrift Fuer Physiologische Chemie. 1984 Mar;365(3):405-14. Review of alleged reaction to monosodium glutamate and outcome of a multicenter double-blind placebo-controlled study. Geha RS, Beiser A, Ren C, et al. The Journal of Nutrition. 2000 Apr;130(4S Suppl):1058S-62S. Executive summary from the report: analysis of adverse reactions to monosodium glutamate (MSG). Federation of American Societies for Experimental Biology. The Journal of Nutrition. 1995 Nov;125(11):2891S-2906S..

No matter where you stand on the topic, it's important to investigate where information is coming from and how valid it is. And if you ever experience symptoms you think may be related to an MSG allergy, consult a doctor.

This article was originally produced as part of 75toGo, a project to publish research-intensive health and fitness stories for twentysomethings looking to create good practices and habits for the decades ahead.

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