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MSG & Food Intolerance: A Hidden Culprit Causing Allergy-Like Symptoms

MSG & Food Intolerance: A Hidden Culprit Causing Allergy-Like Symptoms

9 minute read time

Monosodium glutamate (MSG) has a fascinating journey spanning a century of culinary and scientific history. In 1908, Japanese chemist Kikunae Ikeda made a groundbreaking discovery while investigating the unique savoury taste of kelp broth. He successfully isolated glutamate as the compound responsible for this distinctive flavour, which he named “umami,” and subsequently developed a method to synthesise MSG.[1] A year later, commercial production of MSG began.

The popularity of MSG spread rapidly across Asia in the early 20th century, first gaining traction in Japan and later expanding to China by 1918. Its journey to Western markets took a different path, entering the United States through Hawaii in the 1920s, driven by Japanese immigrant communities. While it didn’t immediately catch on in American home kitchens, MSG found its way into processed foods, frozen meals, and canned soups by the 1950s, fundamentally changing commercial food production.

Today, MSG remains one of the most widely used flavour enhancers globally, with an estimated annual production of 2 million tons.[1] Despite its widespread use and the FDA’s designation as “generally recognised as safe” (GRAS), MSG has become a subject of ongoing debate and scrutiny. Its presence in our food supply ranges from fast-food restaurants to packaged snacks, highlighting its enduring influence on modern food production and consumption patterns.

Early studies quickly claimed MSG as toxic and harmful, especially in large quantities. However, these poorly conducted studies are now seen as flawed, reshaping the perception MSG has on the human body. Still, many report food intolerance symptoms associated with MSG consumption, making it a particularly perplexing ingredient with much to discover.

What is Monosodium Glutamate (MSG)?

Monosodium glutamate (MSG) is a flavour enhancer composed of sodium and glutamic acid, an amino acid that occurs naturally in many foods. The compound consists of 78% glutamate, 12% sodium, and 10% water, forming a white, crystalline powder that readily dissolves in water.

The chemical formula for MSG is C5H8NO4Na, existing as separate sodium cations and glutamate anions in zwitterionic form when in solid state. When dissolved in water, it separates into sodium and free glutamate, similar to how table salt dissolves into its component ions.

Modern MSG production primarily relies on bacterial fermentation, a process similar to making yoghurt or wine. The process begins with carbohydrate-rich sources like sugar cane, sugar beets, or corn, which are fermented by specialised bacteria to produce glutamic acid. This glutamic acid is then purified, neutralised with sodium hydroxide, and crystallised to create the final MSG powder.

Can You Develop an MSG Sensitivity?

MSG sensitivity can develop at any age, as demonstrated by documented cases where individuals who previously consumed MSG without issues later developed adverse reactions. In one notable case, a patient experienced no allergic symptoms from MSG-containing foods before age 13, only to develop sensitivity in her teenage years[2].

The prevalence of MSG sensitivity reactions has been a subject of scientific investigation, though exact numbers remain difficult to establish. Studies examining self-reported MSG sensitivity have shown varying results. In one comprehensive study, among 61 participants who believed they were MSG-sensitive, approximately 36.1% reacted to MSG, while 24.6% reacted to placebo, and 9.8% responded to both. The severity and nature of reactions typically increase with higher doses, particularly when MSG is consumed without food, with 2.5 grams appearing to be a threshold dose for reactivity in sensitive individuals[3].

While many people claim sensitivity to MSG, controlled scientific studies have found that documented cases of true MSG reactions are less common than perceived sensitivity would suggest. Most foods with added MSG contain less than 0.5 grams of the additive, though, in heavily seasoned restaurant meals, consumption can reach up to 5 grams or more. The average daily intake is estimated to be between 0.3-1.0 grams for most people.[4] Interestingly, research has shown that many individuals who self-report MSG intolerance often have incomplete or incorrect knowledge about what MSG is and which foods contain it.[5]

Is Sensitivity to MSG a Food Allergy or Intolerance?

MSG sensitivity is primarily classified as a food intolerance rather than a true food allergy, as it typically does not involve an IgE-mediated immune system response. The reaction occurs when the digestive system has difficulty processing MSG, leading to various symptoms without triggering the body’s immune defences.

A true food allergy involves the immune system’s overreaction to a food protein through IgE antibodies, which can trigger severe reactions even with minimal exposure. 

MSG intolerance manifests through a collection of symptoms known as “MSG symptom complex,” which typically occurs when consuming more than 3 grams of MSG.

Rare Type I Allergic Reactions

While extremely rare, a groundbreaking case study has documented the first confirmed instance of a Type I allergic reaction to MSG. The case involved a woman who experienced tongue swelling and oral symptoms, confirmed through skin prick testing and oral challenge tests. Histological examination revealed mast cell infiltration and other markers consistent with a true allergic response.[2]

The distinction between MSG intolerance and allergy is crucial for proper diagnosis and management. While most people who react to MSG experience intolerance symptoms, the possibility of a true allergic reaction, though extremely rare, should not be completely dismissed.

What are the Symptoms of MSG Sensitivity?

MSG sensitivity can manifest through a diverse range of symptoms, typically appearing within two hours of consuming foods containing MSG. The severity and combination of symptoms can vary significantly from person to person, with some experiencing mild discomfort while others face more intense reactions.

Common Digestive Symptoms

The digestive system often bears the brunt of MSG sensitivity, with symptoms including:

  • Bloating
  • Gas
  • Diarrhea
  • Abdominal pain
  • Nausea

Neurological and Sensory Symptoms

Many people experience neurological effects, such as:

  • Headaches
  • Facial pressure or tightness
  • Numbness or burning sensations in the mouth, face, or neck
  • Tingling skin

Systemic Reactions

Some individuals may experience broader systemic symptoms including:

  • Facial flushing
  • Excessive sweating
  • General weakness
  • Drowsiness
  • Heart palpitations
  • Chest pain

The intensity of symptoms typically correlates with the amount of MSG consumed, with reactions being more pronounced when MSG is consumed on an empty stomach or in quantities exceeding 3 grams. While most symptoms are mild and self-limiting, some individuals may experience more severe reactions requiring medical attention.

It’s worth noting that less than 1% of the general population appears to be particularly sensitive to MSG. When symptoms do occur, they typically resolve on their own without requiring specific treatment, though staying hydrated and resting can help manage mild symptoms.

What is MSG Symptom Complex?

MSG symptom complex, formerly known as “Chinese Restaurant Syndrome,” refers to a collection of symptoms some people report experiencing after consuming foods containing monosodium glutamate. This condition first entered medical discourse in 1968 through a letter published in the New England Journal of Medicine, describing symptoms like headaches and palpitations after eating at Chinese restaurants.

Despite widespread anecdotal reports, scientific evidence linking MSG to these symptoms remains limited. In a notable study of self-identified MSG-sensitive individuals, 36.1% responded to MSG, while 24.6% reacted to placebo, suggesting that some reactions might be psychosomatic.[6] Research has indicated that symptoms typically occur when consuming more than 3 grams of MSG on an empty stomach, while most foods contain less than 0.5 grams of the additive.

The condition’s original naming and subsequent stigma have been recognised as problematic, rooted in xenophobic attitudes toward Asian cuisine. Recent research suggests that many early studies claiming MSG’s harmful effects were poorly designed and influenced by cultural biases.

The U.S. Food and Drug Administration has consistently maintained MSG’s status as “generally recognised as safe,” and multiple controlled studies have failed to establish a clear causal relationship between MSG and reported symptoms.

When symptoms do occur, they typically arise a couple of hours after MSG consumption and often include:

  • Headache and facial pressure
  • Numbness or burning sensations
  • Flushing and sweating
  • Heart palpitations
  • General weakness
  • Nausea

The severity and combination of symptoms vary among individuals, with reactions being more pronounced when MSG is consumed without food. While most symptoms are mild and self-limiting, the mechanism behind these reactions remains unclear, though research indicates it does not involve an IgE-mediated immune response typical of true food allergies.

Effects of MSG on the Digestive System

MSG interacts with the digestive system in several complex ways, beginning the moment it enters the mouth. When consumed, MSG activates glutamate receptors in the mouth, triggering increased salivation and signaling the presence of protein in the brain.

Gastric Function

MSG consumption stimulates increased gastric acid secretion, which can affect overall digestive function. Research has shown that regular consumption of MSG in doses of 15-30 mg/kg can lead to changes in stomach acid production and potentially impact the gastric mucosa.[7] However, some studies suggest that MSG may actually accelerate gastric emptying by facilitating duodenal motility in certain individuals.[8]

Gut Microbiota Impact

MSG significantly influences gut microbiota composition. Studies have revealed that MSG administration can alter the balance of intestinal bacteria, affecting the ratio of Firmicutes to Bacteroidetes – a key indicator of metabolic health. It can decrease beneficial bacteria like Akkermansia, which plays a crucial role in maintaining gut barrier function.[9] However, some recent research suggests that low doses of MSG might actually have probiotic-like benefits by promoting intestinal development and regulating intestinal flora.[10]

Barrier Function

MSG can affect the integrity of the intestinal barrier by influencing mucus secretion and tight junction proteins. Research has shown decreased levels of ZO-1 (a tight junction protein) and altered expression of antimicrobial peptides in MSG-treated subjects, potentially compromising gut barrier function.[9] This disruption may contribute to increased intestinal permeability and subsequent inflammatory responses.

Intestinal Sensitivity

Recent studies have demonstrated that MSG exposure can increase visceral sensitivity, particularly in individuals with pre-existing digestive conditions. This heightened sensitivity may explain why some people experience more pronounced digestive symptoms after consuming MSG-containing foods.[11]

What Foods are High in MSG?

MSG occurs naturally in many foods and as an added ingredient in processed products. Recognising which foods contain MSG can help you make better dietary choices that align with your diet.

Naturally Occurring MSG

Foods with the highest natural concentrations of free glutamates include:

  • Parmesan cheese
  • Roquefort cheese
  • Dried shiitake mushrooms
  • Green peas
  • Corn

Fermented and Aged Products

These products naturally develop high MSG content through the fermentation process:

  • Soy sauce 
  • Fish sauce 
  • Miso
  • Aged cheeses

Processed Foods with Added MSG

Common processed foods containing added MSG include:

  • Fast food items (particularly at KFC, Chick-fil-A, Wendy’s, and McDonald’s)
  • Frozen meals and pizzas
  • Canned soups and soup mixes
  • Processed meats (hot dogs, lunch meats, beef jerky)
  • Seasoning blends and condiments

Asian Cuisine Ingredients

Traditional Asian cooking ingredients often contain significant amounts of MSG:

  • Oyster sauce
  • Kimchi
  • Seaweed product

Snack Foods

Popular snack items frequently containing added MSG:

  • Potato chips (especially flavoured varieties)
  • Flavored popcorn
  • Trail mix
  • Crackers

How Can You Tell if Food Contains MSG?

Identifying MSG in food products requires careful label reading, as it can appear under various names. The FDA mandates that added MSG must be listed as “monosodium glutamate” in the ingredient panel. However, MSG can also be present through other ingredients that naturally contain or produce it.

Common MSG Indicators

Look for these ingredients on food labels:

  • Hydrolysed protein
  • Autolysed yeast
  • Yeast extract
  • Hydrolysed vegetable protein (HVP)
  • Soy extracts
  • Protein isolate

Be aware that claims like “No MSG” or “No Added MSG” can be misleading if the product contains ingredients that naturally have MSG. Products containing ingredients with natural MSG cannot legally claim “No MSG” on their packaging, even if no additional MSG was added.

Remember that naturally occurring MSG in foods like tomatoes, cheeses, and mushrooms doesn’t require specific labelling, making it impossible to completely avoid glutamates in your diet.

How Do You Remedy MSG Symptoms?

Most MSG symptoms are generally moderate and self-limiting, but several effective remedies can help alleviate discomfort while the compound leaves your system.

The most important immediate step is to increase your water intake. Drinking plenty of water helps flush MSG from your system and can reduce symptom duration. For nausea relief, drinking ginger or peppermint tea can be beneficial.

Several medications can help manage specific symptoms:

  • Antihistamines for breathing difficulties or facial swelling
  • Pain relievers for headaches
  • Anti-nausea medication for digestive discomfort

Additional remedies include:

  • Getting adequate rest while symptoms persist
  • Taking vitamin B6 (50 mg) which may  help process MSG into harmless byproducts
  • Temporarily avoiding sodium-rich foods and beverages, which may interfere with the body’s ability to flush out MSG

Most people experience relief within a few hours of symptom onset. However, if symptoms are severe or persist beyond 48 hours, seeking medical attention is recommended. For those experiencing chest pain, difficulty breathing, or severe swelling, immediate emergency care is necessary.

Can You Treat or Cure MSG Sensitivity Long-Term?

While there is no permanent cure for MSG sensitivity, several long-term management strategies can help minimise reactions and improve quality of life. The most effective approach is a combination of preventive measures and lifestyle modifications.

Vitamin B6 Supplementation

Research suggests that vitamin B6 supplementation may help reduce MSG sensitivity. Taking 50 mg of vitamin B6 daily for at least 12 weeks has shown promising results, with studies indicating that eight out of nine people experienced reduced reactions to MSG with this treatment.

Prevention Through Diet

The most reliable long-term strategy remains careful dietary management:

  • Maintain a detailed food diary to identify trigger foods
  • Read ingredient labels thoroughly
  • Communicate with restaurant staff about MSG content
  • Consider working with a dietitian to develop a sustainable meal plan

Natural Protection

Some natural compounds may offer protective effects against MSG sensitivity, including:

  • Calendula officinalis
  • Green tea
  • Ginkgo biloba
  • Antioxidant vitamins

While MSG sensitivity can be challenging to manage, most people can successfully control their symptoms through careful dietary choices and preventive measures. The FDA continues to classify MSG as “generally recognised as safe,” and there is no evidence of long-term health problems from MSG consumption.

However, individuals who experience severe reactions should consult with healthcare providers for personalised management strategies. Food intolerance tests are a great tool as well to have in your arsenal to better detect and protect yourself from unwanted food reactions.

Scientific References:

  1. Sano C. History of glutamate production. Am J Clin Nutr. 2009 Sep;90(3):728S-732S. doi: 10.3945/ajcn.2009.27462F. Epub 2009 Jul 29. PMID: 19640955.
  2. Osada R, Oshikata C, Kurihara Y, Terada K, Kodama Y, Yamashita Y, Nakadegawa R, Masumitsu H, Motobayashi Y, Takayasu H, Masumoto N, Manabe S, Zhu Y, Tanaka R, Kaneko T, Sasaki A, Tsurikisawa N. A Case of Type I Food Allergy Induced by Monosodium Glutamate. J Asthma Allergy. 2024 Mar 7;17:161-165. doi: 10.2147/JAA.S451911. PMID: 38469567; PMCID: PMC10926854.
  3. Yang WH, Drouin MA, Herbert M, Mao Y, Karsh J. The monosodium glutamate symptom complex: assessment in a double-blind, placebo-controlled, randomised study. J Allergy Clin Immunol. 1997 Jun;99(6 Pt 1):757-62. doi: 10.1016/s0091-6749(97)80008-5. PMID: 9215242.
  4. Niaz K, Zaplatic E, Spoor J. Extensive use of monosodium glutamate: A threat to public health? EXCLI J. 2018 Mar 19;17:273-278. doi: 10.17179/excli2018-1092. PMID: 29743864; PMCID: PMC5938543.
  5. Pavia, Carmen. “Reactions to MSG.” Royal Prince Alfred Hospital Allergy Unit, University of New South Wales, November 2001
  6. Yang WH, Drouin MA, Herbert M, Mao Y, Karsh J. The monosodium glutamate symptom complex: assessment in a double-blind, placebo-controlled, randomised study. J Allergy Clin Immunol. 1997 Jun;99(6 Pt 1):757-62. doi: 10.1016/s0091-6749(97)80008-5. PMID: 9215242.
  7. Falalieieva TM, Kukhars’kyÄ­ VM, Berehova TV. [Effect of long-term monosodium glutamate administration on structure and functional state of the stomach and body weight in rats]. Fiziol Zh (1994). 2010;56(4):102-10. Ukrainian. PMID: 20968043.
  8. Teramoto H, Shimizu T, Yogo H, Nishimiya Y, Hori S, Kosugi T, Nakayama S. Gastric emptying and duodenal motility upon intake of a liquid meal with monosodium glutamate in healthy subjects. Physiol Rep. 2014 Jan 6;2(1):e00187. doi: 10.1002/phy2.187. PMID: 24744869; PMCID: PMC3967673.
  9. Zhang, Li, et al. “Quercetin Ameliorates Gut Microbiota Dysbiosis That Drives Hypothalamic Damage and Hepatic Lipogenesis in Monosodium Glutamate-Induced Abdominal Obesity.” Frontiers in Nutrition, vol. 8, 2021, Article 671353
  10. Xu J, Tang M, Liu Y, et al. Safety assessment of monosodium glutamate based on intestinal function and flora in mice. Food Science and Human Wellness, 2022, 11(1): 155-164. https://doi.org/10.1016/j.fshw.2021.07.016
  11. Bailey, J. A. Brant, et al. “Dietary Monosodium Glutamate Increases Visceral Hypersensitivity in a Mouse Model of Visceral Pain.” Neurogastroenterology & Motility, vol. 35, no. 4, Apr. 2023, article e14596. 
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