Monosodium glutamate (MSG) is a flavor enhancer used in countless processed and restaurant foods. Derived from glutamic acid, an amino acid naturally found in many foods like cheese and tomatoes, MSG is often added to boost savory, or "umami," flavor. Despite decades of controversy and anecdotal reports, robust scientific evidence consistently finds MSG to be safe for the general population in moderation. However, for a small percentage of individuals, consumption can trigger a mild, short-lived reaction known as MSG symptom complex.
Understanding MSG Sensitivity and Symptoms
MSG sensitivity is not a true food allergy, which involves an immune system response. Instead, it is a food intolerance that can cause a collection of symptoms, typically appearing within two hours of consuming a large dose of MSG—often more than 3 grams—on an empty stomach. Most meals with added MSG contain less than 0.5 grams, making a high dose less common but still possible in heavily seasoned restaurant or processed meals.
Common Symptoms of MSG Symptom Complex
- Headache: One of the most frequently reported symptoms.
- Flushing and Sweating: Facial redness and sweating can occur.
- Numbness or Burning: A tingling or burning sensation in the face, neck, and chest area is common.
- Palpitations: A rapid or fluttering heartbeat can be a symptom.
- Nausea: Feelings of sickness are reported by some sensitive individuals.
- Weakness: A general feeling of fatigue or muscle aches can follow ingestion.
Who Should Consider Avoiding Monosodium Glutamate?
While most people can consume MSG without issue, certain individuals and groups should consider limiting their intake. It’s important to distinguish between those with a diagnosed sensitivity and those who may have been influenced by past misinformation, such as the debunked myth of "Chinese Restaurant Syndrome".
Individuals with a Diagnosed or Suspected Sensitivity
- If you have consistently and reproducibly experienced the symptoms of MSG symptom complex after consuming MSG-containing foods, avoidance is the most straightforward management strategy. A controlled oral challenge, supervised by a healthcare professional, is the only reliable way to confirm an MSG sensitivity.
People on Sodium-Restricted Diets
- MSG is the sodium salt of glutamic acid, meaning it contains sodium, albeit significantly less than table salt. Individuals with conditions like hypertension (high blood pressure) who are advised to reduce sodium intake should be mindful of all sources of sodium, including MSG. While MSG can be used to reduce overall sodium while maintaining flavor, those with strict restrictions must monitor their total intake from all sources, including processed foods where MSG is common.
Asthmatics with a History of Adverse Reactions
- Early reports in the 1980s suggested a link between MSG and bronchospasm in some individuals with asthma. However, subsequent, more rigorous studies have failed to provide conclusive evidence of this link in stable asthmatics. Still, if you have severe or unstable asthma and suspect MSG as a trigger, it is prudent to discuss this with your doctor and avoid it as a precaution.
A Caution for Highly Processed Foods
- MSG is a convenient ingredient for many ultra-processed foods. Even if MSG itself is not the primary concern, the foods it is typically added to—such as pre-packaged snacks, frozen meals, and canned goods—are often high in other less-healthy ingredients like saturated fat, sugar, and high levels of sodium from sources other than MSG. Avoiding these types of products is a healthy dietary choice for most people, regardless of MSG sensitivity.
The Difference Between Added and Natural Glutamate
It is important to remember that glutamate is a naturally occurring amino acid found in many whole foods. The glutamate in MSG is chemically identical to the glutamate found naturally in food, and the body metabolizes both in the same way.
| Feature | Added Monosodium Glutamate (MSG) | Naturally Occurring Glutamate |
|---|---|---|
| Source | Produced via fermentation of corn, sugar beets, sugar cane, or molasses. | Found naturally in protein-rich foods and vegetables. |
| Examples | Seasoning mixes, soups, processed meats, flavored chips. | Tomatoes, mushrooms, Parmesan cheese, cured meats, soy sauce. |
| Labeling | Must be listed as "monosodium glutamate" or "flavor enhancer (621)". | Does not need to be explicitly listed as MSG on a label. |
| Sensitivity Trigger | Symptoms most often associated with high doses ingested alone. | Not typically associated with adverse reactions at normal intake levels. |
How to Identify and Reduce Added MSG
For those who need or wish to reduce their MSG intake, careful label reading is crucial. The FDA requires added MSG to be listed on ingredient panels. However, many products contain naturally high levels of glutamate or other ingredients that are sources of free glutamate.
Here are some common terms to look for on ingredient labels:
- Monosodium Glutamate: The direct listing for added MSG.
- Hydrolyzed Vegetable Protein: A product broken down into amino acids, including glutamate.
- Autolyzed Yeast Extract: A concentrated source of natural glutamate.
- Yeast Extract: Another source of naturally occurring glutamate.
- Soy Protein Isolate or Concentrate: Processed soy products that can contain free glutamate.
For restaurant and takeout food, where MSG is not required to be labeled, it's best to inquire directly with staff about its use if you have a sensitivity.
Conclusion
While science overwhelmingly supports the safety of MSG for most people, those with a confirmed sensitivity, certain medical conditions, or a general desire to reduce intake of processed foods should be mindful of their consumption. By understanding the symptoms of MSG symptom complex and learning to identify MSG on food labels, you can make informed dietary choices that align with your personal health needs. If you suspect an MSG sensitivity, consulting a dietitian or healthcare provider can help you create an effective management plan.
For further information on food additives, you may consult authoritative sources such as the FDA's guidance on the topic.
Resources for Managing MSG Sensitivity
- Read Labels Carefully: Look for "monosodium glutamate" or other glutamate-containing ingredients like "hydrolyzed protein".
- Ask at Restaurants: Since restaurant food isn't required to be labeled, ask if they use MSG, especially at fast-food or highly seasoned food establishments.
- Favor Whole Foods: Focus on fresh, unprocessed foods, as they generally don't contain added MSG.
- Cook at Home: Preparing meals yourself gives you complete control over ingredients and seasoning.
- Be Aware of Natural Glutamates: Some sensitive individuals may need to be mindful of foods with naturally high glutamate levels, such as aged cheeses, tomatoes, and mushrooms.
