Q: I have an intolerance to mono-sodium glutamate and get a severe headache 12 to 14 hours after ingesting MSG-containing food. Glutamic acids and maltodextrin found in processed food products also cause the same reaction. I have no problem with unprocessed foods such as tomatoes and milk. Despite avoiding these foods, I still occasionally get the same symptoms after eating out. How can I identify the additive that may be causing it? Lorraine
A: Food additives are substances that are commonly added to foods to help flavour, colour or preserve them. Common additives include sulphites (found in wine, soft drinks, dried fruit, salads), antioxidants (found in fats and oils), aspartame (artificial sweetener), nitrates/nitrites (in processed meats), food colourants (known as E100-180) and MSG or monosodium glutamate, a flavour enhancer, (known as E621).
Some additives play an essential part in keeping our food safe, but others may be responsible for unpleasant reactions.
MSG was first added to Western food in 1948, and is now one of the world's most widely used additives. It is commonly found in Chinese food, packet soups, canned vegetables, and processed meats. Ever since its introduction, there have been reports of reactions, known as the ''Chinese restaurant syndrome''.
The symptoms may include shortness of breath, heart palpitations, chest pain, or swelling of the lips or throat.
Although there is little convincing scientific evidence to link MSG with this type of reaction, if you do suffer any of these symptoms, you may have a true allergy, and it is essential to seek immediate medical advice.
The type of reaction you get, Lorraine, is much more likely to be an intolerance to MSG than an allergy. Intolerance is different, and fortunately less severe. In medical terms, it is not classified as an allergy because it is not an IgE-mediated body response.
Unfortunately, this means that allergy tests, such as skin prick or blood testing, cannot help to diagnose it.
It is thought that 0.1 to 1.5 per cent of the population may suffer from food-additive intolerance.
The following symptoms can all be associated with an intolerance to food additives:
- Headaches or migraines.
- Tightness in the chest, neck and face.
- Flushing and sweating.
- Heart palpitations.
- Chest pain.
- Nausea and other gut symptoms.
The symptoms are usually mild and don't require any medical intervention. However, in some people they can be quite debilitating. If you think you may have an intolerance to an additive, keep a detailed food diary, looking carefully at what you have eaten during the preceding 24 to 48 hours. This should allow any patterns to emerge, and then you may be able to start eliminating things in your diet to test your theory.
If you manage to identify the likely additive that is causing your symptoms, it is important to avoid it completely.
The Food Standards Australia and NZ (FSANZ) requires that any foods containing MSG clearly state that on the label, so it may be as simple as reading the labels of the foods you eat. However, some people who are intolerant of MSG may also need to avoid foods containing free glutamate. Free glutamate can combine with free sodium in your body to create MSG, and lead to the same symptoms of intolerance.
Foods that contain natural glutamate include:
- Other fruit juices.
- Cheese, especially parmesan and roquefort.
Other glutamates can be added to foods, and may cause the same problems, including monopotassium L-glutamate (E622), calcium glutamate (E623), monoammonium L-glutamate (E624) and magnesium glutamate (E625). Autolysed yeasts can also be implicated - these are found in Vegemite, Marmite, and Oxo.
Last, you mention maltodextrin. This is a sweetener frequently found in soft drinks and sweet products. It contains free glutamic acid and may cause the same problems for people with an intolerance. It is important to check the label for all of these additives if you think you suffer from MSG or glutamate intolerance.
As mentioned, traditional allergy tests are of no help. I recommend consulting a specialist dietician, who will be able to give you further advice, and you could consider making an appointment with an allergy specialist.
If your symptoms are severe enough, they may discuss the possibility of carrying out a double-blind placebo-controlled capsule challenge.
This is a complicated test, but could help you work out if it is the glutamate that is causing your symptoms, or whether there are other avenues you need to explore.
- Cathy Stephenson is a general practitioner, medical forensic examiner and mother of three. If you have a question for her, email firstname.lastname@example.org
- © Fairfax NZ News
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