E518 - Magnesium sulphate

At a glance

• What it is: An inorganic magnesium salt; often found as colorless crystals called Epsom salt.
• What it does: Works as a firming agent and as a nutrient source of magnesium; used under good manufacturing practice rules.
• Where you’ll find it: Selected processed foods and some fortified beverages or mixes; also common in dietary supplements.
• Dietary notes: Vegan, gluten‑free, and allergen‑free; has a naturally bitter, saline taste.

Why is Magnesium sulphate added to food?

Food makers use magnesium sulphate for two main reasons. First, it can act as a firming agent, helping fruits and vegetables keep their texture after processing. Second, it supplies magnesium, so it may be used as a nutrient supplement where allowed. In the United States, magnesium sulfate is affirmed as GRAS (Generally Recognized As Safe) for use in food at levels consistent with GMP (good manufacturing practice).¹

What foods contain Magnesium sulphate?

Use and levels vary by country and food type. In the EU, magnesium sulphate is an authorised food additive listed as E518, with conditions of use set in EU law and assessed by the European Food Safety Authority (EFSA).² In the U.S., it can be added to foods under GRAS and GMP provisions for its intended functions.¹

You may encounter it in:

• Products fortified with minerals (as a magnesium source)
• Certain processed fruits and vegetables (for texture)
• Some dry mixes and beverage bases

If present, it will appear on the ingredient list as “magnesium sulphate,” “magnesium sulfate,” or “E518.”

What can replace Magnesium sulphate?

Possible substitutes depend on the job it needs to do:

• For magnesium fortification: magnesium chloride or magnesium oxide
• For firming: calcium chloride or calcium sulphate
• For salt reduction strategies: potassium chloride

Always choose replacements that are permitted for the food type and purpose in your market.

How is Magnesium sulphate made?

Food‑grade magnesium sulphate is produced by neutralizing sulfuric acid with a magnesium base such as magnesium oxide or magnesium carbonate, followed by crystallization and drying. It occurs as white crystals or a crystalline powder and is used in accordance with food‑grade specifications.¹ The most common form in commerce is the heptahydrate, MgSO4·7H2O, widely known as Epsom salt.³

Is Magnesium sulphate safe to eat?

Yes, when used as intended. In the U.S., magnesium sulfate is affirmed as GRAS for specified technical effects and must be used under GMP, which limits the amount to the minimum needed for the effect.¹ In the EU, EFSA re‑evaluated E518 and concluded there is no safety concern at the reported uses and use levels as a food additive.²

Very high intakes of magnesium from non‑food sources (such as some supplements or laxatives) can cause gastrointestinal effects like diarrhea. The U.S. National Institutes of Health (NIH) sets a tolerable upper intake level (UL) for supplemental magnesium at 350 mg/day for adults; this UL does not include magnesium naturally present in foods.⁴

Does Magnesium sulphate have any benefits?

As a food additive, its “benefit” is mainly technological (firming) or nutritional (supplying magnesium). Magnesium is an essential mineral involved in nerve and muscle function, energy metabolism, and normal heart rhythm.⁴ When used for fortification, magnesium sulphate contributes to total magnesium intake within regulatory limits.

Who should avoid Magnesium sulphate?

• People with kidney disease should be cautious with extra magnesium from supplements or magnesium‑containing salts, because impaired kidneys may not clear excess magnesium well.⁵
• Individuals who are sensitive to magnesium‑containing laxatives or who experience diarrhea from magnesium salts should avoid additional supplemental magnesium; typical amounts in foods used under GMP are far lower than medicinal doses.⁴
• If you take medicines that interact with magnesium (for example, certain antibiotics or thyroid medicines), take them at a different time from magnesium supplements. Ask a healthcare professional for advice.⁴

Myths & facts

• “It’s just bath salt.” Fact: Epsom salt used for bathing is the same chemical, but only food‑grade material meeting food specifications should be used in foods.
• “It’s a preservative.” Myth: Magnesium sulphate is not used to preserve foods from spoilage; its main roles are firming and mineral fortification.
• “It tastes like table salt.” Myth: It has a distinctly bitter, saline taste, so it is used sparingly.
• “All magnesium additives are the same.” Myth: Different magnesium salts behave differently in foods; makers choose among options like magnesium chloride or magnesium oxide depending on the goal.

Magnesium sulphate in branded foods

Look for “magnesium sulphate,” “magnesium sulfate,” or “E518” in the ingredient list. It tends to appear in specialized products rather than everyday staples. If you are checking a specific item, the package label is the most reliable source.

References

Footnotes

1. 21 CFR 184.1447 — Magnesium sulfate. U.S. Food and Drug Administration (eCFR). https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-184/subpart-B/section-184.1447 ↩ ↩² ↩³ ↩⁴

2. Re‑evaluation of magnesium sulphate (E 518) as a food additive. EFSA Journal. European Food Safety Authority. https://www.efsa.europa.eu/en/efsajournal/pub/5864 ↩ ↩²

3. Magnesium sulfate — Compound Summary. PubChem, National Institutes of Health. https://pubchem.ncbi.nlm.nih.gov/compound/Magnesium-sulfate ↩

4. Magnesium — Fact Sheet for Health Professionals. National Institutes of Health, Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/ ↩ ↩² ↩³ ↩⁴

5. Magnesium in diet and safety considerations. MedlinePlus, National Library of Medicine (NIH). https://medlineplus.gov/ency/article/002423.htm ↩