E528 - Magnesium hydroxide

At a glance

• What it is: An alkaline mineral compound with the formula Mg(OH)2 that neutralizes acids.
• What it does in food: Acts as a pH control agent (acidity regulator) to reduce acidity.
• Where you might see it: Ingredient lists as “magnesium hydroxide” or “E528.”
• Dietary notes: Mineral-based, vegan-friendly, and free from common allergens.
• Use levels: Added at very low levels under good manufacturing practice.

Why is Magnesium hydroxide added to food?

Food makers use magnesium hydroxide to raise or stabilize pH. In U.S. regulations it is affirmed as GRAS—Generally Recognized As Safe—for use in food as a pH control agent, with amounts limited by GMP (good manufacturing practice).¹

What foods contain Magnesium hydroxide?

E528 appears in niche applications where a mild base is needed, such as adjusting the acidity of certain beverages, confections, or mineral waters. Because it is used sparingly and only when a pH increase is desired, it is less common than other pH regulators. Labels typically list it by name or as E528 in regions that use E-numbers.

What can replace Magnesium hydroxide?

Substitutes depend on the goal (raising or lowering pH, processing needs, taste):

• To raise pH (make less acidic): calcium hydroxide, sodium hydroxide, potassium hydroxide, magnesium oxide, sodium carbonates, potassium carbonates, or calcium carbonates.
• To lower pH (make more acidic): acids such as citric acid are often used instead.

Choice hinges on taste impact, solubility, labeling preferences, and the product’s recipe.

How is Magnesium hydroxide made?

Commercial magnesium hydroxide is typically produced by:

• Precipitating magnesium from seawater or brines using lime (calcium hydroxide), which forms solid Mg(OH)2 that is filtered and washed.²
• Hydrating magnesium oxide (MgO) to Mg(OH)2.

In the European Union, E528 refers specifically to magnesium hydroxide meeting the purity and identity criteria set out for food additives, including the chemical formula Mg(OH)2.³

Is Magnesium hydroxide safe to eat?

Yes—when used as intended. In the United States, magnesium hydroxide is affirmed as GRAS (Generally Recognized As Safe) for use in foods as a pH control agent, with no specific maximum level other than good manufacturing practice.¹ As a magnesium source, excessive intake from supplements or medications can cause loose stools; the tolerable upper intake level (UL) for supplemental magnesium in adults is 350 mg/day, not counting magnesium naturally present in foods.⁴

Does Magnesium hydroxide have any benefits?

Its benefit in foods is technological: it helps control acidity, which can protect flavor, texture, and stability. Outside foods, magnesium hydroxide is a well-known active ingredient in over-the-counter antacid products that neutralize stomach acid,⁵ and it is also used as a saline laxative.⁶ These drug uses involve much higher amounts than those used as a food additive.

Who should avoid Magnesium hydroxide?

• People with kidney disease should be cautious with magnesium-containing products because the body may have difficulty clearing excess magnesium.⁴
• Anyone taking magnesium-based antacids or laxatives should follow label directions and medical advice to avoid excessive intake.⁶
• Individuals who experience gastrointestinal upset (e.g., diarrhea) from supplemental magnesium should minimize extra sources.⁴

Myths & facts

• Myth: “E528 is a synthetic chemical.” Fact: Magnesium hydroxide is an inorganic mineral compound; it can be made from natural brines or seawater.
• Myth: “If it’s in foods, it works like a laxative.” Fact: Food use levels are tiny and intended for pH control, not a medicinal effect.
• Myth: “All bases taste soapy.” Fact: Choice of base matters; magnesium hydroxide is used carefully to manage pH without imparting off-flavors when formulated correctly.
• Fact: The same substance can have different roles. In drugs it’s an active ingredient; in foods it’s a processing aid and acidity regulator.

Magnesium hydroxide in branded foods

Use varies by country and product type. If present, you’ll see “magnesium hydroxide” or “E528” on the ingredient list. Because pH regulators are used only when needed, many foods will not contain it. To check specific products, scan the label or the manufacturer’s website for E-number listings.

References

Footnotes

1. 21 CFR 184.1427 Magnesium hydroxide — U.S. FDA eCFR. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-184/subpart-B/section-184.1427 ↩ ↩²

2. Magnesium Compounds — U.S. Geological Survey, Mineral Commodity Summaries 2023. https://pubs.usgs.gov/periodicals/mcs2023/mcs2023-magnesium-compounds.pdf ↩

3. Commission Regulation (EU) No 231/2012 — EU specifications for food additives. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32012R0231 ↩

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

5. 21 CFR 331 Antacid drug products for over-the-counter human use — U.S. FDA eCFR. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-D/part-331 ↩

6. 21 CFR 334 Laxative drug products for over-the-counter human use — U.S. FDA eCFR. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-D/part-334 ↩ ↩²