What Is MSG Symptom Complex?

MSG Allergies
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Monosodium glutamate (MSG) is a food additive suspected of causing reactions such as headache, flushing, and heart palpitations. People who experience such a reaction may mistake it for an MSG allergy, but it actually is not. MSG symptom complex is different than an allergy and not clearly understood.

What Is MSG? 

A common flavoring added to Chinese food, canned vegetables, soups, and processed meats, MSG is the sodium salt of glutamic acid. Found naturally in seaweed, tomatoes, and cheese, MSG flavoring was developed from a boiled down version of a savory seaweed broth. Today, it is made by fermenting starch, sugar beets, sugar cane, or molasses.

MSG has been used as a flavor enhancer for more than a century and is responsible for the umami taste in many dishes. It is approved as a food additive by the U.S. Food & Drug Administration (FDA) with the designation of “generally regarded as safe.” However, many people have reported experiencing uncomfortable symptoms after eating foods containing MSG.

Symptoms of MSG Symptom Complex

Previously referred to as Chinese restaurant syndrome, MSG symptom complex is a cluster of adverse reactions often mistaken for a food allergy. It is not a true allergy, but rather a food intolerance.

Most people who have the syndrome experience only mild and short-lasting symptoms after consuming MSG. These may include:

Headaches

While research into MSG symptom complex is limited, there have been several reports of people experiencing headaches after consuming MSG. Studies suggest the food additive may have a connection to headaches. Although the mechanism isn't entirely understood, research has found people with migraines and tension-type headaches have higher levels of glutamate than those without migraines. While this does not confirm a causal link between migraines and MSG, it may help to explain the phenomenon of headaches after consuming MSG.

In addition, research shows MSG consumption can cause blood pressure to rise, which is linked to headaches. However, in studies this increase has been short-lived and only occurs following MSG intake that is much higher than what is normally consumed in a meal.

Asthma

Research in the 1980s found a suspected link between MSG and asthma. In a small study published in the Journal of Allergy and Clinical Immunology, 32 people with asthma were put on an additive-free diet for five days, then given 500 milligrams of MSG in a hospital setting.

The MSG challenge provoked reactions in 13 people, with six experiencing symptoms of asthma and MSG symptoms complex within two hours of ingestion, and another seven experiencing asthma flare-ups within 12 hours. These results, however, have not been replicated in further studies. 

A 1999 study of 100 people with asthma found no indication that MSG provokes asthma attacks based on diagnostic markers including forced expiratory volume (FEV1) values.

People with asthma—with and without a history of self-diagnosed Chinese restaurant syndrome—were given 2,500 milligrams of MSG. Researchers found no clinically relevant changes in FEV1 levels and advised maintaining a “healthy skepticism about the existence of MSG sensitivity in individuals with asthma.”

Causes

MSG symptom complex is not very well understood. The reactions people experience after eating MSG do not involve traditional allergy pathways that activate an immune response.

Because sensitivity to MSG is not a true allergy, there is no test available to determine whether you are sensitive to it.

Furthermore, despite widespread anecdotal evidence that some people experience reactions, studies of MSG have not demonstrated a clear cause-and-effect relationship.

Only a handful of studies have found mild reactions can occur after consuming large amounts of MSG and the threshold for symptom development is far above what would be consumed during a normal meal.

Diagnosis

MSG symptom complex is typically diagnosed based on symptoms appearing following MSG consumption. Your doctor may ask questions such as:

  • Have you eaten Chinese food within the past two hours?
  • Have you eaten any other food that may contain monosodium glutamate within the past two hours?

They may also perform tests, such as an electrocardiogram to check for abnormal heart rhythms and spirometry to test airflow.

Treatment

There is no specific treatment for MSG symptom complex, although over-the-counter medications can be used to treat individual symptoms during an episode. For example, Tylenol (acetaminophen) or Excedrin (aspirin, acetaminophen, and caffeine) may ease a headache.

More serious symptoms may be life-threatening and require immediate medical attention. Get emergency medical help right away if you experience any of the following, as they can be indications of life-threatening allergic reactions known as anaphylaxis. Although MSG isn't known to cause anaphylaxis, it's possible a person may be allergic to a food that contains it:

  • Chest pain
  • Heart palpitations
  • Shortness of breath
  • Swelling of the lips or throat

Avoiding MSG

The most effective strategy for avoiding symptoms is to not consume MSG if you suspect you may be sensitive to it.

While there is little scientific evidence to support a link between MSG and reactions, the FDA requires food labels to list MSG as an ingredient. Foods that naturally contain MSG do not need to list MSG as an ingredient, although the product label cannot claim "No MSG" or "No added MSG."

MSG Labeling

If you are avoiding MSG, check the ingredients list for the following:

  • Monosodium glutamate
  • Hydrolyzed vegetable protein
  • Autolyzed yeast
  • Hydrolyzed yeast
  • Yeast extract
  • Soy extracts
  • Protein isolate
  • Tomatoes 
  • Cheese

Dining out while avoiding MSG can be trickier. You can always ask if the meal is prepared with MSG and many Chinese restaurants advertise they are MSG-free.

A Word From Verywell

Despite the belief that there is such a thing as an MSG allergy, there is a lack of hard scientific data to link common reactions to MSG. That said, sometimes misconceptions exist for a reason and there is likely some truth underlying the MSG phenomenon that experts simply have not yet figured out. If you suspect foods containing MSG give you a headache or other unpleasant symptoms, by all means, avoid them.

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