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Sulphites: the Asthma culprit

Few people know that there are preservatives in foods like sulphites which can trigger breathing difficulties in asthma patients. In many countries, sulphites are recognised as potential allergens and labelling them clearly on the product label is required by law. In India, the standards are much more relaxed. 

What is it that makes packaged food last so long without getting spoilt? It is the preservatives that are hidden behind innocuous-looking numbers on the food product label. One of the most common preservatives found in jams and fruit drinks are ‘sulphites’. ‘Sulphites’ consist of a group of sulphur-based chemicals. While sulphites are generally added to processed foods, they are also used to keep cut fruits and vegetables looking fresh. Dried fruits also get a liberal dose of sulphites for preservation purposes. In wine, sulphites are produced during fermentation and are also added directly after fermentation which helps to preserve wine over long periods.

Sulphites compounds are shown below with their International Numbering System Number (E Number):
  • Sulphur dioxide (E220)
  • Sodium sulphite (E221)
  • Sodium hydrogen sulphite (E222)
  • Sodium metabisulphite (E223)
  • Potassium metabisulphite (E224)


How to avoid sulphites 

  • Always read the label of prepackaged food products for sulphites to avoid them, particularly if you are asthmatics or allergic to aspirin. Look at the E-numbers.
  • Avoid fast food outlets and restaurants where food is not prepared on the premises because generally cut vegetables are kept in sulphites solution to prevent them from getting discoloured/brown.

Allergy to sulphites is not uncommon. Sulphites are strongly associated with asthma attacks. Foods containing sulphites may cause breathing difficulty within minutes after eating them. Asthmatics and people with allergies to aspirin have an elevated risk for reaction to sulphites. The reaction can be fatal and requires immediate treatment. The reaction includes sneezing and swelling of the throat. Sulphites also destroy vitamin B1 (thiamine) and folic acid in the body.

The World Health Organization (WHO) has acknowledged that sulphites are problematic for some people. In the UK sulphites are one of the potential allergens that have to be labelled on a food or drink products where Sulphur dioxide (E220) is at levels above 10 mg per kilogram or 10 mg per litre (ppm). As per Food Standards Australia New Zealand (FSANZ), it is also mandatory to mention sulphites on labels of all foods with sulphite concentrations of 10 mg per kilogram or more.

The Food & Drugs Administration (FDA), USA, has placed several restrictions on the use and labelling of sulphites. These include:
  • Forbidding sulphites from being added to foods intended for raw consumption (such as salad bars).
  • Requiring that sulphites in excess of 10 ppm (parts per million) be indicated on food labels, whether those sulphites are naturally occurring or added during manufacturing.
  • Requiring that sulphites added for purposes such as preserving foods be labelled, regardless of whether they are in concentrations higher than 10 ppm.

The phrase “contains sulphites” is necessary on packaged foods with a sulphite content above 10 ppm.

In July 2008, the Canadian Federal Government also proposed amendment to the Food & Drug Regulations, that would require the label to contain a declaration of added sulphites when they are present in prepackaged products in amounts greater than 10 parts per million (ppm). 
Under the Indian law Prevention of Food Adulteration (PFA) Rules, 1955 use of sulphurous acid including salts there of, are allowed in certain categories of food preparations up to specified limit of the final food or beverage. This is done under the heading “Class II preservative” (Addition of Class II preservatives in any food is restricted unless other wise provided in the rules). Maximum allowed limits for various foods varies from 40 ppm to 2000 ppm as sulphur dioxide. Generally manufacturers declare sulphites on the label as “contains Class II preservative” with E number in the bracket. The caution on allergy is not provided. 

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