Mind the MSG

Many people love Chinese food for its spicy and sour tastes. Our takeaways regularly include Chinese food like Manchurian, noodles and fried rice. But Chinese food contains artificial taste enhancers, sweeteners, colouring and other additives, one of which is monosodium glutamate (MSG).

It is used in Asian foods, processed meat, poultry and other products to enhance flavours. But not many know that allergies to MSG are highly possible and can lead to fatal consequences. These reactions could be a symptom of what is often referred to as the ‘Chinese Restaurant Syndrome’.

MSG interacts at the level of either the central or peripheral glutamate receptors and increases the excitatory and stimulatory mechanisms that cause these reactions. Several ongoing studies and research activities are examining the details of how MSG causes these allergic reactions and how to manage them.

Mild adverse reactions

The self-limited or mild adverse reactions due to oral ingestion of MSG include a burning sensation in the neck, forearms and chest, facial pressure or tightness, headache, nausea, palpitation, numbness in the neck radiating to arms and back, chest pain, tingling and warmth in areas of face, back, neck, arms and temple, drowsiness and weakness. Bronchospasm or difficulty in breathing is observed only in asthmatics.The self-limited reactions occur between MSG levels of 0.5-2.5 gm.

In some individuals, a dose-related response to three gm or more of MSG given without food has been observed. To date, asthma is the only documented predisposing medical condition that is associated with the adverse effects from ingestion of MSG.

Life-threatening reactions

The serious or life-threatening reactions due to oral ingestion of MSG include anaphylaxis, seizures, dysrhythmias, hypovolemic shock and fainting spells with marked fall in blood pressure and constricted throat. The serious or life-threatening complications occur at levels higher than 2.5 gm.

The typical reported interval of such reactions is between 15 to 60 minutes but in some asthmatics, it can take up to 6 to 12 hours for the symptoms to manifest.

Identifying sensitivity to MSG is extremely difficult. The only way to determine this is to feed the person MSG-laden food and observe him for as long as 48 hours after the meal. Similarly, diagnosing MSG sensitivity is also extremely difficult. This is because none of the symptoms of MSG toxicity is caused exclusively by it. In most cases, it is caused in combination with other food additives. In addition, these reactions are dose-related.

MSG is often hidden in food. The difficulty in diagnosing it is compounded by the illegal advertising of ‘No MSG’ or ‘No   added MSG’ on labels when the products do contain it. Hence, it is advisable that the consumer should be aware of this, and in a case of emergency, rush to the nearest healthcare facility.

(The author is MD, director, Quantified Health, Grow, Bengaluru)