Indian Journal of Allergy, Asthma and Immunology

: 2021  |  Volume : 35  |  Issue : 2  |  Page : 43--47

Sulphites in food & drinks in asthmatic adults & children: What we need to know

Mukesh Kumar Gupta1, GV Basavaraj2,  
1 Department of Paediatrics, JNUIMSR, Jaipur, Rajasthan, India
2 Department of Paediatrics, Indira Gandhi Institute of Child Health, Bengaluru, Karnataka, India

Correspondence Address:
Dr. Mukesh Kumar Gupta
61/226, Sect 6, Jagriti Marg, Sect. 6, Pratap Nagar, Jaipur - 302 033, Rajasthan


Sulfites are commonly used preservatives and additives in the food and pharmaceutical industries. Many people develop adverse reactions to them which may vary from mild skin rash to life-threatening anaphylactic reactions. However, asthma exacerbation is the most commonly linked problem. The possibility of sulfite sensitivity should be considered when individuals demonstrate asthma symptoms following the consumption of sulfite-containing foods (such as dried fruits and wines in adults and packaged food in children such as biscuits, chips, and packaged drinks) or adverse skin reactions following the use of cosmetics or medicated creams. In fact, many of the mild-to-moderate asthma cases in children can be cured by just avoiding the packaged/preserved/processed food and beverages. Food that has no additives at all is to be preferred particularly if it is to be consumed by children. It is best to eat a preservative-free diet if at all possible by adults as well if required natural food preservatives should be used.

How to cite this article:
Gupta MK, Basavaraj G V. Sulphites in food & drinks in asthmatic adults & children: What we need to know.Indian J Allergy Asthma Immunol 2021;35:43-47

How to cite this URL:
Gupta MK, Basavaraj G V. Sulphites in food & drinks in asthmatic adults & children: What we need to know. Indian J Allergy Asthma Immunol [serial online] 2021 [cited 2022 Aug 19 ];35:43-47
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Food preservatives and additives are the substances added directly or indirectly in known quantities to various food items before their final consumption. Some artificial colors are also added to the foods to give them an appealing look. When the food is to be stored for a prolonged period, the use of additives and preservatives is essential to maintain its quality, wholesomeness, taste, appearance, and flavor.[1],[2] Nowadays, most people tend to eat one or more ready-made foods available in the market. Such foods contain some kind of additives and preservatives so that their quality and flavor are maintained and they are not spoiled by bacteria and yeasts. Artificial flavors and flavor enhancers are the largest class of additives. Direct additives are the substances added to a food for a specific purpose and the manufacturer has to include their details on the labels. Indirect food additives are usually not included in food labels and they are added to food in miniature amounts unintentionally during handling, packaging, or storage. This stage, where these additives are added may include the production, processing, treatment, packaging, transportation, or storage of food and the purposes of adding these may be improving shelf life, maintain its quality, wholesomeness, taste, appearance, and flavor and prevents food spoilage due to fungal or bacterial growth. There are more than 3000 food preservatives and additives used as antimicrobial agents, antioxidants, preservatives, coloring agents, chelating agents, food acids, pH control agents, anticaking agents, leavening agents, antifoaming agents, bulking agents, color retention agents, emulsifiers, glazing agents, stabilizers, thickeners, sweeteners, curing agents, and nutrient supplements.[1],[2],[3] Here is a simple example – wheat is ground in such a way to remove the brown-colored portion that is rich in vitamins and minerals, to produce white flour. Hence, to restore the nutritive value, thiamine, nicotinic acid, iron, and calcium are added to the flour. There is a yellowish tint in freshly ground wheat flour and yields weak dough that produces poor bread. Baking properties as well as the color of the flour improve by storing it for several months before making bread.

The majority of the food additives which are commonly used by manufacturers has adverse health effects on the consumer and many of these may have potentially life-threatening side effects.[4],[5],[6] The harmful health effects could be acute and they can also be hazardous in the long term on frequent exposure. Immediate effects may include headaches, changes in energy level, and alterations in mental concentration, behavior, or allergic reactions including asthma exacerbations. Occupational exposures to the sulfites have also been reported to cause persistent skin symptoms. Long-term effects such as increased risk of cancer, cardiovascular disease, and other degenerative conditions have also been reported.[1],[2] Some studies implicate synthetic preservatives and artificial coloring agents as aggravating factors for attention deficit hyperactivity disorder symptoms in those affected. In our clinical practice also, we have found children consuming excess fast food and packaged food to be hyperreactive as compared to other children on traditional food and this hyperreactivity settles down few months after stopping or reducing these food items.

 Sulfites the most Important Culprit

Among the food additives and preservatives, sulfiting agents have been most commonly reported and have been linked with asthma.[7],[8],[9],[10] The term sulfite is commonly used for sulfur dioxide (SO2) and its salts – potassium metabisulfite, sodium metabisulfite, potassium bisulfate, sodium bisulfate, and sodium sulfite. These are extensively used in the food and pharmaceutical industry – most commonly as preservatives, antibrowning agents, and antioxidants. They are practically omnipresent salts because they serve multiple functions hence it is very difficult to avoid them in the modern era.

Sulfites are reported to cause a variety of allergic symptoms and signs which includes abdominal pain, diarrhea, dermatitis, urticaria, flushing, hypotension, and bronchoconstriction in asthmatic patients. They may also trigger anaphylactic reactions.[1],[2] Although sulfite sensitivity may present in many ways, respiratory symptoms (predominantly among asthmatics) are most frequent. The severity of sulfite-induced asthmatic symptoms varies from person to person and ranges from mild to very severe and may be life-threatening at times. The actual prevalence of sulfite sensitivity in individuals with asthma is not known; however, the reported prevalence varies from 3% to 10%.[2],[5],[10] Poorly controlled asthma patients are at increased risk of untoward reactions to sulfite-containing foods. There is some evidence to show that respiratory sign symptoms are more common in females and children.[2],[8]

 Mechanisms of Adverse Reactions to Sulfites

Since there are a wide range of clinical presentation and varying sensitivities and severity of reactions to different forms of sulfites, no single mechanism can explain all these reactions to these additives.[10],[11],[12],[13] One possible explanation is that SO2 gas being an irritant and reflex contraction of the airways following inhalation could result in asthma symptoms. This may in particular explain the rapid onset of symptoms following ingestion of liquids such as beer or wine when SO2 gas is inhaled during the swallowing process.[5],[7] Second, the enzyme sulfite oxidase is required for their metabolism; it helps break down sulfite to sulfate by oxidation. The level of this enzyme in some patients is adequate for metabolizing endogenous sulfites but may be insufficient when an exogenous overload of ingested or inhaled sulfite is present. The resulting sulfite excess would then trigger the bronchospasm. Thus, some people with asthma who react to sulfites may have a partial deficiency of this enzyme resulting in excessive accumulation of them and thereby cholinergic-mediated bronchoconstriction. It has also been suggested that Vitamin B12 is able to catalyze the extracellular nonenzymatic oxidation of sulfites; hence, it might prevent sulfite accumulation and therefore the induction of bronchospasm in sulfite-sensitive patients. Simon et al. have reported to completely blocking the appearance of bronchospasm in four patients with sulfite-sensitive asthma and partially blocking in two of six patients who were administered cyanocobalamin before the oral challenge test with sulfites.[11],[12] Thus, increased demands for B12 to metabolize the dietary sulfites could be a possible reason for the widespread deficiency of Vitamin B12 nowadays, apart from low dietary intake.

Many individuals may have immunoglobulin E (IgE)-mediated allergy reflected by positive skin tests to sulfites; however, others may have non-IgE-mediated direct release of mediators from mast cells such as histamine and others.[13] There is some evidence that leukotriene receptor antagonists may inhibit SO2-mediated bronchoconstriction in asthmatic individuals which suggests a possible role of prostaglandins and leukotrienes in sulfite-induced asthma. Recently, another mechanism by which sulfite additives can affect individuals with asthma has been reported is by altering the gut microbiota.[14] The disturbance in the gut microbiome by antimicrobials and other factors has been linked to asthma. Two commonly used food preservatives, sodium bisulfite, and sodium sulfite were tested for their bactericidal and bacteriostatic effects on four bacterial species. These species are members of the healthy human gut microbiome and are commonly used as probiotics. Within few hours of exposure to sulfites in concentrations between 250 and 500 ppm, a significant reduction in cell numbers for all bacteria types was observed. These observations suggest that alteration of gut microbiota and subsequent alteration in the gut–lung axis may lead to worsening asthma in individuals chronically exposed to sulfite-containing food.

 Exposure to the Sulfite Additives

People are exposure to sulfites primarily by intake of foods and drinks, where sulfites are used for preservation. There is a long list of sulfite-containing food items often consumed by the majority of children and many adults. Apart from being cheap and convenient, the sulfites are extremely versatile and their addition to foods serves multiple purposes. The use of cosmetics and medicines is the other sources of sulfite exposure in addition to food [Table 1].[1],[2]{Table 1}

 How much Sulfite Exposure is too much?

Internationally, the highest permissible limits of sulfites in food products are advised by the Codex Committee on Food Additives as the General Standards for Food Additives (GSFA) and termed as the maximum permissible limit (MPL). In our country, the Food Safety and Standards Authority of India (FSSAI) is the body to regulates the sulfite content in food products.[3],[15] As per the GSFA, sulfite content is advised to be 50–500 mg/kg in solid food products and in liquid food products 50–200 mg/kg. Although the upper limits of these preservatives have been set by the FSSAI in our country for various food items, many other frequently consumed items have been left. Moreover, adverse reactions including anaphylaxis are known to occur even at concentrations below MPLs in sensitive individuals. An acceptable daily intake (ADI) of 0–0.7 mg/kg b.w./day had been assigned for SO2 and its salts by the Joint Food and Agriculture Organization/WHO Expert Committee on Food Additives. The ADI was based on a long-term three-generation study of reproductive toxicity in rats.[16] When a person is consuming many food items containing sulfite preservatives, even with the sulfite content of the food within the guidelines, the average total daily intake may be much higher than suggested ADI. Unfortunately, there is a scarcity of published data in our country on total sulfite intake based on the assessment of sulfite levels in foods and beverages which makes it difficult to estimate the exposure levels. The only published Indian study evaluating the sulfite content in commonly consumed food products was conducted in Delhi. Food products evaluated in this study were procured from the local supermarkets and specialized stores at various places in Delhi and the National Capital Region. The products included all the commonly available brands multinational, national, local brands, and also unbranded ones in which the addition of sulfites is permitted and also those not mentioned in the regulatory list. Unbranded food products sold loose by pushcart retail vendors were also included in the study. Although the majority of food products assessed contained sulfite levels in the range advised by the FSSAI; however, many food items which are very frequently consumed by children such as fruit bars, fruit digestives, jams, raw sugar, refined sugar, dessert toppings, ready-to-serve beverages, and liquid glucose were found to have sulfite levels higher than the permitted MPL. The sulfite content of the food items such as potato snacks, jams/marmalades, bakery products (biscuits/crackers), ice creams, and cakes/pastries was higher as compared to many other countries (Australia, New Zealand, Italy, Korea, China, and Italy), and unfortunately, these are the ones which are frequently ingested and also gifted to children.[3] Furthermore, the MPLs given by the FSSAI for these food products are higher as compared to other countries. Hence, even with the same amount of packed food consumption, exposure to these additives will be higher in our children. Although the use of sulfites in fresh salads, fruit salads, and mincemeat or sausage meat, is not permissible in many countries, it may occur illegally adding to the cumulative exposure. Hence, even with the sulfite content well below the MPL, it is easy to exceed the ADI when only one type of sulfite-containing food is consumed in high quantity. Hence, if many of such sulfite-containing foods are consumed then it is very easy to exceed the MPL. This is very relevant and is of high importance in the currently changing food habits of our children not only in urban areas but also in rural children as well. Vitamin B12 deficiency could add to the problem by hampering the extracellular nonenzymatic oxidation of sulfites.

Considering the varied mechanism underlying sulfite sensitivity, unavailability of commercially available tests to measure the blood levels or IgE antibodies to sulfites or solution to test them by skin prick method, clinicians have to depend on their clinical acumen to suspect and manage the sulfite sensitivity. Clinicians may empirically eliminate the sulfite and other additive-/preservative-containing foods from the diet for a limited period and reintroduce them after few months ago into the diet to assess the efficacy of removal. However, diets involving the removal of multiple additives and food chemicals have the very great potential to lead to nutritional deficiency, especially in the pediatric population. However, any dietary intervention should be adapted to the individual's dietary habits and should ensure nutritional demands are met. Ultimately, a healthy diet free of chemicals and preservatives should be the aim for all patients. The Indian Academy of Pediatrics and research institutes should take the initiative to know the extent of the problem and to bring attention of appropriate authorities to regulate the sulfite content of the food items and spread awareness not only among clinicians but also in parents and caregivers. Research in the field has shown that appropriate dietary behavior can be inculcated among children and has been shown to improve asthma control in children.[17],[18]

 Why anyone should not Eat Packaged Food

It contains sulfites/additives/coloring agents – Direct damageIt contains saturated and trans fats – Pro-inflammatoryRefined carbs – Inflammation andCheese and dairy product/animal fatNo fibersNo flavonoidsNo Vitamin CHigh blood sugars.

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Conflicts of interest

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