What do sulphates in food do to your body?: Clarifying the confusion

October 29, 2025 •

4 min read

According to Food Standards Australia New Zealand, sulphites are naturally occurring minerals often used as food additives to prevent spoilage and preserve colour. These preservatives, often confused with sulphates, can cause adverse reactions in some sensitive individuals, while sulphates themselves have different dietary roles.

Quick Summary

Sulphites are food preservatives that trigger allergic-like symptoms in sensitive people, especially asthmatics. In contrast, naturally occurring sulphates in water cause a laxative response in high doses and have distinct dietary roles from the essential sulfur-containing compounds found in proteins.

Key Points

Distinguish Sulphites from Sulphates: Sulphites are common food preservatives that can cause reactions in sensitive people, while sulphates are natural mineral salts with different bodily effects.
Sulphite Sensitivity is Common in Asthmatics: A significant number of asthmatics experience allergic-like symptoms, including wheezing and chest tightness, when consuming sulphites.
High Water Sulphate Causes Laxative Effects: Consuming drinking water with unusually high concentrations of sulphates can cause a mild laxative effect and dehydration in some individuals.
Sulphites are Widely Used: They are found in many products, including dried fruits, wine, processed meats, and condiments, and must be declared on food labels in many regions.
Sulphur is an Essential Nutrient: The body needs sulfur, which it gets from sulfur-containing amino acids in protein-rich foods like meat, eggs, and cruciferous vegetables.
Management Involves Avoidance: The most effective way to manage sulphite sensitivity is to identify and avoid food and drinks containing the preservative.

Unpacking the Confusion: Sulphates, Sulphites, and Your Diet

The terms 'sulphates' and 'sulphites' are often used interchangeably, leading to widespread confusion, especially when it comes to food. In reality, these are distinct chemical compounds that affect the body in different ways. Sulphates, or sulfates, are mineral salts that are generally harmless in dietary amounts and are found naturally in water and some foods. Sulphites, on the other hand, are compounds containing sulfur dioxide and are widely used as food preservatives. Understanding the difference is key to managing potential sensitivities and appreciating the full role of sulfur in your body.

The Key Distinction: Sulphates vs. Sulphites

The primary confusion stems from their shared sulfur component. However, their chemical structure and biological effects are significantly different. Sulphites are a primary concern for food sensitivity, while sulphates are typically harmless in food and water, except in very high concentrations.

Sulphites (SO3): Preservatives with a Purpose

Sulphites act as preservatives, antioxidants, and anti-browning agents in the food industry. They are added to a wide array of products to prevent microbial growth and extend shelf life. When consumed, they can release sulfur dioxide gas, which is the main culprit behind irritant and allergic-like reactions in sensitive people. Food manufacturers are required to declare the presence of sulphites on ingredient labels, especially since they are considered a major food allergen in many countries, including the UK and Canada.

Sulphates (SO4): Essential and Environmental

As mineral salts of sulfuric acid, sulphates are present in drinking water, certain minerals, and are also used in various industrial and personal care products. While not typically added directly to food for preservation, they are naturally present in water sources. At high concentrations in drinking water, sulphates can impart a bitter taste and cause a mild laxative effect, particularly in those unaccustomed to it. The average person consumes significantly more sulphates from food and endogenous metabolism than from water. Sulphates are also vital for many bodily functions, including detoxification and maintaining gut health.

The Impact of Sulphites on the Body

For most people, consuming sulphites is entirely safe. However, a significant portion of the population, particularly asthmatics, can experience sensitivity reactions. The body's inability to efficiently process sulphites, often due to a deficiency in the enzyme sulphite oxidase, can lead to a buildup of sulphites and trigger symptoms. The resulting release of sulfur dioxide can lead to respiratory irritation and other issues.

Common Symptoms of Sulphite Sensitivity

Symptoms can range from mild to severe, and they do not involve the immune system in the same way as a true allergy, but can mimic allergic reactions.

Respiratory: Wheezing, coughing, chest tightness, shortness of breath.
Gastrointestinal: Abdominal pain, cramps, nausea, and diarrhoea.
Dermatological: Hives (urticaria) and skin rashes.
Other: Headaches, flushing, and in very rare cases, anaphylaxis.

Dietary Sources of Sulphites to be Aware Of

Sulphites are found in a surprising number of food and drink products. If you have a sensitivity, reading labels carefully is essential. Common sources include:

Dried fruits: Apricots, raisins, and prunes.
Wines and Beers: Used during fermentation to stop the process and preserve flavour.
Processed potatoes: Frozen french fries, dried potatoes.
Vinegars: Particularly wine and cider vinegar.
Condiments: Bottled sauces, mustard, horseradish.
Fruit and Vegetable Juices: Bottled lemon, lime, and grape juice.
Canned Goods: Many canned fruits and vegetables.
Sausages and Processed Meats: Used to preserve colour and extend shelf life.

Comparison: Sulphites vs. Sulphates


Feature	Sulphites (SO3)	Sulphates (SO4)
Dietary Source	Added preservatives, some natural foods	Naturally present in water and some foods
Primary Function	Preservative, antioxidant in food	Essential bodily functions, laxative in high doses
Health Concerns	Sensitivity reactions (asthma, rashes, GI issues)	Laxative effect in high concentrations in water
Key Mechanism	Releases irritant sulfur dioxide gas	Mineral salt balance, detoxification pathways
Labeling	Must be declared on food labels	Generally not explicitly labeled, except in water reports

The Essential Role of Dietary Sulphur

While avoiding sulphites is necessary for sensitive individuals, it's important not to confuse them with essential dietary sulfur. The body requires sulfur for many vital processes, primarily obtained from sulphur-containing amino acids like methionine and cysteine. These amino acids are crucial for protein synthesis, detoxification, and the production of important bodily compounds. Good sources of dietary sulfur include:

Meat and poultry
Fish and seafood
Eggs and dairy products
Legumes
Cruciferous vegetables (broccoli, cauliflower)
Allium vegetables (onions, garlic)

Conclusion

The impact of dietary sulphates and sulphites on your body is nuanced and dependent on their form and concentration. Sulphites are food preservatives that can trigger adverse reactions in a sensitive subgroup of the population, with asthmatics being particularly at risk. The best way to manage this sensitivity is through diligent label reading and avoidance. Conversely, sulphates are natural mineral salts with different effects; while high concentrations in water can have a laxative effect, normal dietary levels are generally safe and essential for health. It is vital to differentiate between the two to maintain a balanced nutritional approach and avoid unnecessary dietary restrictions. Paying attention to food labels and consulting a healthcare professional for persistent symptoms can help you determine your individual tolerance levels and nutritional needs.

Frequently Asked Questions

Sulphites are sulfur-based compounds added to food as preservatives to prevent spoilage and browning. Sulphates are natural mineral salts present in water and some foods, and they do not serve a preservation purpose.

Common sources of sulphites include dried fruits (apricots, raisins), wines, canned vegetables, processed meats like sausages, condiments, and some juices.

Sulphite sensitivity can cause allergic-like symptoms such as wheezing, coughing, chest tightness, hives, abdominal pain, nausea, and, in rare cases, anaphylaxis.

Yes, high concentrations of sulphates in drinking water can cause a mild laxative effect, particularly in those who are not used to it. It can also impart a bitter taste to the water.

Sulphite reactions are not considered true allergies because they do not typically involve the immune system's IgE antibodies. They are usually irritant or pharmacologic reactions, though they can mimic allergic symptoms.

In many countries, food manufacturers are required to declare sulphites on the ingredient list, often emphasized in bold, if they are present above a certain threshold.

Yes, dietary sulfur is essential. It is primarily obtained from sulfur-containing amino acids like methionine and cysteine, found in protein-rich foods. Sulfur is necessary for protein synthesis, detoxification, and overall health.

The best management strategy is avoidance. For severe sensitivity, a doctor may recommend an elimination diet or patch testing under medical supervision. Asthmatics with sensitivity should ensure their condition is well-managed.