A few months ago, I had the opportunity to write a piece about the nutritional implications of monosodium glutamate (MSG) for 75togo.com. You can view the original article on that site by clicking here, or you can visit the abridged version I posted on the Huffington Post. The full text is printed below, so read on to learn all about the MSG controversy and what it means to you.
You’ve probably heard mixed reviews about monosodium glutamate (MSG). Perhaps you’ve heard it’s perfectly safe. Or maybe you’ve heard it causes mild problems for people who have a sensitivity to it. Or maybe you’ve heard that it’s a toxic chemical that’s slowly killing us all. The internet is full of conflicting perspectives. To set the record straight, I’ve taken a close look at the large body of scientific research and spoken with the US Food and Drug Administration (FDA) and Ajinomoto (the world’s first producer of MSG) to learn what you need to know 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, each of which are present in the foods we eat every day: sodium (found, for example, in table salt) and glutamate (an amino acid). Glutamate is naturally abundant in our own bodies and in the foods we eat. It is not inherently harmful, and is vital to a wide range of biological functions.6 The human body can even create its own glutamate, so consuming glutamate in your diet isn’t necessary—though it may be difficult to avoid, since glutamate is a natural component of nearly every food protein.6
When sodium (a positively charged molecule) is combined with a negatively charged molecule, the result is called a “sodium salt”. For example, table salt (sodium and chloride) is the sodium salt of chloride. MSG (sodium and glutamate) is the sodium salt of the amino acid glutamate.2,3
The History of MSG Discovery and Production
MSG was first isolated in 1908 by Japanese scientist Kikunae Ikeda, who was searching for the compound that gave dashi (a Japanese soup base made from seaweed and fish) its distinct flavor. Eventually he was able to determine that glutamate, which occurs naturally in dashi broth, was the source. He successfully isolated and crystallized it7,8 and described the unique taste of MSG as umami, which roughly translates to delicious.7,8,9 In the year following his discovery, Ikeda and his partner founded Ajinomoto and began producing MSG for use in food.4
Over 100 years later, Ajinomoto and other modern-day manufacturers produce MSG through the fermentation of corn, sugar cane and/or tapioca.3 According to Dr. Eyassu Abegaz with Scientific and Regulatory Affairs at Ajinomoto North America, Inc., “We began manufacturing MSG in 1909, so the process is quite refined. The finished product must be at least 99% pure monosodium L-glutamate in order to comply with the Food Chemical Codex.” He added, “The glutamate in MSG is so pure that the human body is unable to distinguish it from any other source of free glutamate, such as that from meat or cheese.”
When I asked Dr Abegaz why sodium is added to the glutamate, he replied, “When glutamate and sodium bond, it forms a pleasant-tasting crystalline powder that is easy to use, store and ship.”4
Different forms of glutamate
A quick aside. In the rest of this article, you’ll see various terms like glutamate, L-glutamate, glutamic acid, monosodium glutamate, monosodium L-glutamate, MSG, and umami. In the context of the MSG in food, they all refer to basically the same thing.
But, since some of these terms have been the subject of debate, I’ve included a detailed explanation at the bottom of this article. Scroll down for more information.
Umami—the fifth taste
It has long been suspected that humans have taste receptors specifically designed to detect umami and in 2000, researchers at the University of Miami School of Medicine finally pinpointed them.10 They found that our mouths have L-glutamate receptors (much like we have sweet and bitter receptors) which allow us to specifically recognize umami whenever free glutamate molecules touch our tongues. This has solidified umami’s classification as the fifth basic taste, alongside sweet, sour, salty and bitter.7,10,11
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.7,12 Umami is perhaps best described as a meaty, mouth-filling, richly savory taste.13
In addition to the discovery of taste receptors for MSG on our tongue, scientists have also discovered glutamate receptors in our gut.6,14 It’s presumed that the purpose of these receptors is to signal the brain to prepare for the digestion of protein-rich food.8
This finding 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 signals to our body that we’re consuming the protein our bodies need.7,8,4
Why is MSG added to food?
Almost all MSG added to food is added as a “flavor enhancer,” meaning it improves the perception of other flavors in a dish. MSG tends to enhance salty, savory, and other flavor characteristics, while muting bitterness and sourness. It also tends to unify and balance the flavors of a dish while causing them to linger longer on the tongue. The taste of soups, snack foods, prepared entrees and restaurant-prepared foods can all benefit from added MSG.4,12
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 aid in sodium reduction because it contains 30% less sodium than table salt, but its flavor boosting ability keeps low-sodium foods palatable.12 Usage levels in prepared foods are low, usually 0.1–0.8% by weight, which is similar to the concentration of free glutamate that naturally occurs in foods like tomatoes or Parmesan cheese.14
Other glutamate-rich seasonings, such as yeast extract and hydrolyzed vegetable protein (HVP), can be used to impart umami instead of MSG. Although these ingredients are not literally the same as adding a pinch of crystallized MSG to a food, the flavor enhancement effect is similar.
Yeast extracts and HVPs don’t just taste like straight 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.4 Usually the choice between using MSG and using one of these alternative flavor enhancers is based on: (1) flavor profile, (2) cost (MSG is often the cheapest option, but not always), and (3) labeling—food producers know MSG is unpopular with some consumers, and these alternatives might not trigger the same aversion.
One other flavor enhancer to keep in mind: 5’ nucleotides (five prime nucleotides) are also flavor enhancers, but they don’t contain any glutamate. Usually labeled as “disodium inosinate” and “disodium guanylate,” on food labels, they help our taste receptors pick up on the glutamate signals already in food, such as from meat, cheese or crystallized MSG.4,15 So although 5’ nucleotides are glutamate-free, they’re only used in tandem with glutamate (naturally occurring or added). You won’t see these often because they tend to be more expensive than glutamate-based flavor enhancers, but I wanted to include them here to be thorough.4
Labeling of MSG and other flavor enhancers
Many critics of MSG refer to yeast extracts and HVPs as “Hidden MSG” because they contain significant amounts of MSG but don’t have to be labeled as MSG on food packaging.
This is because the MSG in yeast extracts and HVPs is a component of the yeast or vegetable protein itself; no crystallized MSG is added. The FDA requires companies to list all the ingredients of a product, but not necessarily the components of a single ingredient. For example, “milk” is considered a single ingredient, but companies are not required to also mention each of its constituents (e.g. water, milkfat, casein, whey protein, lactose, calcium).
The most common exception to this rule is if one of the “big eight” allergens is present. If milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, or soybeans are present, food producers are required by law to mention them by their common name on the label at least once.16
The FDA doesn’t require similar labeling practices for MSG because it believes MSG is safe (much more on this later). Furthermore, MSG sensitivity is not an allergy,17,18 and the symptoms generally attributed to MSG are mild and temporary,5,19,2,20 unlike some severe allergic reactions—which can be dangerous.
…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.
Instead, FDA Spokeswoman Marianna Naum, Ph.D. told me that “Flavor enhancers must be listed by common or usual name on a food label [and are] not subject to the provision of the law that allows flavors to be declared collectively…” So at least that means that MSG, HVPs, yeast extracts, and 5’ nucleotides must all be listed individually on the label and can’t be hidden in collective categories like “spices,” or “natural flavors and color.”
However, even though the FDA thinks of MSG as safe, it discourages false advertising. Naum told me that “…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.”
The US Food and Drug Administration (FDA) classifies MSG as “Generally Recognized as Safe” (GRAS).2 According to Naum, “For the use of an ingredient to be eligible for 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 included on the FDA’s GRAS since the list’s initial year, in 1958.5 But, MSG’s GRAS status hasn’t saved it from considerable controversy over the years.
Health claim against MSG: “Chinese Restaurant Syndrome”
In 1968, a Physician wrote in to the New England Journal of Medicine and described a numbness, tingling, warmth, and feeling of tightness 15-60 minutes after eating a meal of Chinese food. The author acknowledged there were many potential causes for his symptoms and merely included MSG-sensitivity as one of them. He called these symptoms “Chinese Restaurant Syndrome,” though it is often referred to today as “MSG Symptom Complex.”21,19 His letter, sparked sparked a flurry of follow-on letters that specifically called out MSG in Chinese food.
Due to growing consumer concern, the FDA and Center for Food Safety and Applied Nutrition (CFSAN) commissioned an independent review of all scientific findings on MSG to offer a conclusive answer to the question: Is MSG dangerous?2,19
That study was performed by the Federation of American Societies for Experimental Biology (FASEB) and was published in 1995 as a supplement to The Journal of Nutrition. The FASEB completed an exhaustive survey of all existing MSG research and literature and consulted with a panel of experts in the field in order to make a conclusive determination on the safety of MSG.2,19 Naum had this to say about the results: “The FASEB report did identify temporary and generally mild symptoms that may occur in some individuals after consuming 3 grams of MSG without food. However, to-date, scientists have not been able to consistently trigger these temporary reactions in studies where MSG was provided with food. Based on the available evidence, FDA considers MSG to be safe for use as an ingredient at normally-consumed levels for the general population.”5
Three grams of MSG is roughly equivalent to a half teaspoon—more than one would ever incidentally ingest without food. If you don’t believe me, try downing a half teaspoon of plain salt by itself and see how well that goes down. According to the FDA website, “An average adult[‘s]…intake of added MSG…estimates at around 0.55 grams per day.”2
When MSG is consumed with food, even mild CRS symptoms become less apparent and repeatable. Basically to cause symptoms, a person would have to consume over five times their typical consumption level and do so without eating any food along with their MSG. And even then, only sensitive individuals would exhibit a reaction.
The FASEB’s findings have been largely confirmed by more recent MSG research, including a large multicenter, double-blind, placebo-controlled, multiple challenge test. Many studies on MSG have been done over the years, but I’ll cover this one specifically because it stands out for both its scope and its rigor.
To highlight the quality of this study, I want to explain what each part of its title means:
- multicenter: Tests were administered in multiple locations to remove any effects due to setting
- placebo-controlled: a sugar pill was randomly administered to some subjects to account for the psychological component of symptoms
- double-blind: neither the researchers nor the test subjects knew which treatment (placebo or MSG) was being administered at a given time
- multiple-challenge: test subjects were repeatedly presented with placebo or MSG within the each testing protocol in order to test repeatability and prevent chance from skewing results.
- plus, it had a large sample size: This test was the largest of its kind—with 110 self-identified MSG-sensitive volunteers completing all protocols for which they were eligible. Many previous studies examined as few as six test subjects. Testing larger groups of people increases the likelihood that the participants of the study are representative of the larger population—in this case, of self-identified MSG-sensitive individuals, which would presumably be the most MSG-sensitive of the general human population.
Test subjects who had an adverse reaction to MSG but not to the placebo in a given protocol were re-challenged with a slightly different test protocol. The four protocols in the study looked at reactivity, threshold dosage, capsule vs. liquid ingestion, and reactivity with food.22 Researchers on this study concluded that:
“…large doses of MSG given without food may elicit more symptoms than a placebo in individuals who believe that they react adversely to MSG. However, neither persistent nor serious effects from MSG ingestion are observed, and the responses were not consistent on retesting.”22
This study confirms what numerous previous studies have also found—that adverse reactions to MSG consumption are rare, mild, temporary and inconsistent, and generally caused by large doses given without food, even in the most sensitive population.22
The scientific consensus on MSG today is that it is one of the most extensively-researched ingredients in our food supply.14
Health claim against MSG: MSG-induced migraines
Another important topic of interest to MSG-sensitive people is migraines. Over recent years, anecdotal reports citing MSG as a migraine trigger have become more common. Migraines are fundamentally different from the CRS symptoms detailed above and so determining if MSG is related to migraines requires its own research.
As a review of MSG research published in a 2010 issue of the peer-reviewed journal Appetite 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.”14
Health claim against MSG: MSG-induced Asthma
The scare about MSG and asthma seems to stem from a series of letter written to the New England Journal of Medicine in the 1980s that once again complained of symptoms after eating at Chinese restaurants. Then, in 1987, a study on 32 subjects with asthma found that 13 of those tested developed asthma after taking pill-based MSG.23
It would be easy to criticize the 1987 study (giving doses of up to 5 grams of MSG in capsule form is not exactly the same as eating food with MSG in it), but that would be beside the point. Studies on asthma and MSG since the 1980s have repeatably and consistently shown no link between asthma and eating MSG.24,25,26,27
The argument has been made that children are particularly sensitive to MSG and that MSG could cause or exacerbate asthma in the young. But, the scientific consensus is that childhood asthma is not linked to MSG.28 A recent study was even done on mice that showed eating MSG had no measurable effect on the lungs that could potentially contribute to asthma symptoms or the development of asthma.29
Are you sensitive to MSG?
In the world of science, causality is a tricky thing to prove. Even if your results do indicate causality, they’re only reliable if you have a large number of test subjects, unimpeachable methods, and (and this one’s the kicker) the results are repeatable. If someone repeats your experiment but gets different results, it suggests that chance (or some other factor) came into play in your initial results. Repeatability has been the main failing/problem for those seeking to establish that MSG is the cause of CRS. Studies that have shown a correlation between MSG and CRS symptoms have failed to show the same correlation when the study is repeated.
The best studies I found on MSG all found that adverse reactions (if any) were inconsistent and not repeatable. That is not to say, however, that no one has ever had an adverse reaction to MSG—just that people who identified as MSG-sensitive didn’t consistently and repeatably react to MSG. And until results are repeatable and consistent, they just don’t carry any scientific weight.
Studies that are unrepeatable carry little or no scientific weight. The FDA is a self-proclaimed “science-based agency”5 and so is bound to respect scientific conclusions over anecdotal evidence. That’s why the FDA has adopted the opinion that MSG is perfectly safe for consumption.
But what about those of us who have seen a friend experience CRS-like symptoms or a migraine after eating food that contains MSG? The lack of scientific evidence that MSG triggers CRS doesn’t necessarily mean that CRS (or something like it) isn’t real—it just means that MSG isn’t causing it in a scientifically measurable way.
If you do think you’re sensitive to MSG, here are some possible scenarios as to what is causing your symptoms:
- You may be sensitive to some part of the food you eat, but not specifically to MSG.
- 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, which is not an allergy.
- You may be sensitive to the high histamine levels present in many Chinese foods, which can sometimes mimic an allergic reaction.18,22,19
- You have a pre-existing vitamin B6 deficiency, which some researchers have speculated is the true cause of CRS symptoms.30,22,19
- You may be experiencing referred pain due to irritation of the esophagus.31
- You have a true sensitivity to MSG (extremely rare).
If you’re experiencing symptoms after eating Chinese food or food containing MSG, your best course of action is to see a doctor, who may then refer you to an allergist, registered dietitian, or other specialist for further testing depending on your symptoms.
A healthcare specialist may then recommend that you try an elimination diet: basically a diet during which you avoid certain foods systematically in order to identify the root cause of a symptom. You may also want to ask your healthcare specialist if adding a vitamin B6 supplement would be a good idea.
Why MSG keeps getting a bad reputation on the internet
Most of the real research I’ve seen against MSG on the internet seems to stem from two sources.
Dr. Russell L. Blaylock’s 1996 book “Excitotoxins: The Taste That Kills” argues that nerve cells in the brain and elsewhere are killed by excessive stimulation of neurotransmitters like glutamate.
The argument for brain damage comes from a 1969 article about MSG injections in days-old mice.32 It should be obvious, but it’s a pretty big mistake to argue that heavy doses of MSG injected under the skin of 2-9 day old newborn mice somehow means the same damage is being done to our bodies when a relatively small amount of MSG is processed through the human digestive system.22,32
It’s true the glutamate is an excitotoxin that can cause brain cell death, but it’s also essential to our brain’s normal function. So far, every paper I’ve read regarding exicitotoxicy is referring only to endogenous glutamate (meaning that which is made by our own bodies), or glutamate that’s been injected or administered in a way that completely circumvents the digestive system. I couldn’t find any paper even arguing that dietary MSG has any effect on brain chemistry. In fact, recent studies have found that 95% of dietary glutamate is metabolized in the digestive tract and turned into fuel or other amino acids.6,33
What little glutamate makes it into the bloodstream is prevented from entering our brains in any significant quantity by the blood brain barrier.34 Given this information, the idea that the MSG we eat somehow travels to the brain and causes neuronal death is a stretch to say the least.
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 1999 review article of MSG research and legislation, she clearly documents the history of food industry influence on research studies, FDA rulings, and suppression of others’ results.35 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.
just because the history of MSG is clouded with politics and agendas doesn’t mean it’s unsafe
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 had 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.
You can read her arguments for yourself at truthinlabeling.org, but most of them stem from decades-old studies (that we have already addressed here), individual informal case reports, and there are often cases of extrapolating data.
If you see anti-MSG information on the internet, check to see whether the arguments stem back to these two sources and whether they take into account the other publicly-available published research.
So why do people continue to condemn MSG even after 40 years of science have failed to show that eating MSG causes harm? Because once fear is ingrained, it’s difficult to completely remove.
Adding to this consumer uncertainty is the fact that the true cause of CRS 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 CRS are caused by referred pain due to irritation of the esophagus.36 Others suspect it could involve a Vitamin B6 deficiency or the high histamine levels present in many Chinese foods.30,22,19
Featured image: [liz west]
Appendix 1: Glutamates—a Glossary
Glutamate, L-glutamate, glutamic acid, monosodium glutamate, MSG, and umami all refer to the same basic thing. Here’s the breakdown:
- Glutamate refers to a salt or isomer of glutamic acid, an amino acid. Glutamate and glutamic acid occur in equilibrium, meaning at any given moment a glutamic acid molecule could become a glutamate and vice versa. Because of this equilibrium, the terms are used interchangeably.
- Monosodium glutamate is abbreviated MSG. There is no difference in definition between these two terms; however, the full name “monosodium glutamate” must be used on food labels that use MSG as a standalone ingredient. Technically speaking, monosodium glutamate is a specific type of glutamate, as several other non-sodium ions could bond with glutamic acid to create a different type of glutamate, e.g. monopotassium glutamate. However, these are far less common in food, and the health issues surrounding MSG have to do with the glutamic acid portion of the molecule, not what ion (e.g. sodium or potassium) is bonded to it.
- When the letter “L” is included, as in the case of L-glutamate, it indicates the chirality (a chemical term indicating asymmetry between a molecule and its mirror image) of the molecule. In food and nature, glutamate is almost always L-glutamate, but in rare cases, can form into its mirror image, which is referred to as D-glutamate. D-glutamate doesn’t trigger umami taste receptors and is extremely rare, so L-glutamate is the relevant molecule when talking about glutamate’s use in food. With the exception of technical research, publications about MSG often drop the “L” because it’s assumed.
- Umami is a term that describes the taste of glutamate, and is often the term of choice in advertising for soy sauce or trendy restaurants. Since umami is triggered by free glutamate,7,10,15 the term umami is almost always referring to free glutamate.
Appendix 2: What to look for if you’re avoiding MSG
We don’t think avoiding MSG is necessary for the average person. However, if you and your healthcare professional believe you could benefit from avoiding it, here are some guidelines from the about how MSG-containing flavor enhancers must be labeled.
- MSG: Naum says, “The common or usual name for the ingredient ‘monosodium glutamate’ is monosodium glutamate.” This means that any food which has had MSG added as a standalone ingredient must include these exact words on the label.
- HVPs and yeast extracts: Naum continues, “The common or usual name of a protein hydrolysate is specific to the ingredient and must include the identity of the food source from which the protein was derived. (21 CFR 102.22) ‘Hydrolyzed wheat gluten,’ ‘hydrolyzed soy protein,’ and ‘autolyzed yeast extract’ are examples of acceptable names. ‘Hydrolyzed casein’ is also an example of an acceptable name, whereas, ‘hydrolyzed milk protein’ is not an acceptable name for this ingredient because it is not specific to the ingredient (hydrolysates can be prepared from other milk proteins). The names ‘hydrolyzed vegetable protein’ and ‘hydrolyzed protein’ are not acceptable because they do not identify the food source of the protein.”
- Foods that naturally contain glutamates. Glutamate is metabolized the same way whether it’s derived from MSG or is naturally occurring.2,19 So if you’re avoiding added MSG, you should also consider avoiding foods that naturally contain high levels of free glutamate. Foods that naturally contain free glutamate or MSG don’t have to specifically mention it on their label. See Appendix 3, below, for a list of common foods which contain free glutamate.
(free glutamate given in mg/100g)
|Shiitake mushroom (fresh)||71||Oyster||137|
|Shiitake mushrooms (dried)||150||Clam||208|
|Green asparagus||49||Snow crab||19|
|Green peas||106||Alaska king crab||72|
|Chicken Egg||15||Cured Ham||340|
|Parmigiano-Reggiano||1680||Fish Sauce (avg)||950|
|Cheddar||182||Soy sauce (avg)||1100|
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