Compared to most other food products, monosodium glutamate (MSG) has a very bad reputation. MSG, the salt form of glutamic acid (a non-essential amino acid), is used as a food additive due to its flavor-enhancing properties. Many people believe MSG causes a number of allergy-like symptoms in a large percentage of the population, including, but not limited to:
- MSG-induced asthma
- migraine headaches
- hives (urticaria)
- swelling of the face, mouth, and tongue (angioedema)
Much of the evidence for so-called "Chinese Restaurant Syndrome" (named for the generous use of MSG in certain types of Chinese cooking) has relied on anecdotal evidence and dubious clinical studies. So what's the truth about MSG? Is it really as bad as it's been made out to be?
Despite the concerns, decades of research have failed to demonstrate a relationship between MSG and the development of serious reactions for most people. In fact, only between one and two percent of Americans have a reaction to MSG, and the vast majority of those people experience only mild symptoms such as tingling skin or a burning sensation in the chest.
Larger doses of MSG have been found to cause symptoms in more people, but those portions are unlikely to show up in either restaurants or in grocery stores. In 1995, the U.S. Food and Drug Administration (FDA) reviewed the evidence and put MSG in the same category as salt and pepper—"generally recognized as safe."
A 2009 study published in the journal Clinical & Experimental Allergy came to a similar finding, concluding: "In short, the current evidence does not suggest that MSG is a signi?cant contributor to asthma, urticaria, angio-oedema, or rhinitis."
That's all good news if a person is among the 98-plus percent of people who can consume MSG without any ill effects. Those sensitive to MSG, however, may experience the following symptoms:
- mild chest pain
- numbness (or burning), especially in and around the mouth
- facial pressure or swelling
More serious symptoms may include:
- chest pain
- heart palpitations
- shortness of breath
- swelling in the throat
Most allergic reactions to MSG are mild and will go away on their own. More serious symptoms, such as anaphylaxis, require emergency treatment in the form of a shot of epinephrine (adrenaline). A person experiencing shortness of breath, swelling of the lips or throat, heart palpitations, or chest pain should proceed to the nearest emergency room immediately.
Foods to Avoid
MSG is difficult to get away from. According to the United States Department of Agriculture (USDA), MSG "is found in virtually all food and, in abundance, in food that is high in protein, including meat, poultry, cheeses, and fish." In addition, labeling is only required when MSG is added as a "direct ingredient." In those cases, it will be referred to as "monosodium glutamate" by the manufacturer.
Other substances to avoid are dried meats, meat extracts, poultry stocks, and hydrolyzed protein, which may be used as binders, emulsifiers, or flavor enhancers. Food labels may refer to these products as "dried beef," "chicken stock," "pork extract," or "hydrolyzed wheat protein."
People with a true allergy to MSG should avoid packaged and processed foods as much as possible and, instead, should choose "raw" foods including fruits, vegetables, and organic meats.
If a clinician suspects MSG may be behind a patient's symptoms, they may ask the following questions:
- Have you eaten any Chinese food within the past two hours?
- Have you eaten any other foods that may contain monosodium glutamate within the past two hours?
Other signs that may confirm a diagnosis of an MSG allergy include:
- rapid heart rate
- abnormal heart rhythm (as confirmed by an EKG)
- reduced air flow into the lungs