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E528 Magnesium hydroxide

E528Acidity regulatorsOrigin: Mineral
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The short answer
Magnesium hydroxide (E528) is a mineral base used to adjust pH in food, and it adds a little magnesium. It is vegan, gluten-free and kosher, though large doses act as a laxative, which is why the same chemical is used as an antacid.
Generally safe

Fine for most people at normal amounts.

E-numberE528
Comes fromMineral
What it doesAcidity regulators
Glycemic index—
Daily limitNot set
Also calledE528, Magnesium hydrate

Rules by country

🇺🇸 US FDAApproved
🇪🇺 European UnionApproved
🇨🇦 Health CanadaApproved
CaliforniaNo extra rules

Permitted in the US, EU and Canada as a pH control agent and mineral source in food processing.

Daily limit: Experts haven’t set a number because normal food amounts are far below any level of concern.

What is it?

Magnesium hydroxide is a weak mineral base that raises pH gently. Food makers use it in processing, and it adds a little magnesium to the product.

Where it comes from: Made by reacting magnesium salts from seawater or brine with an alkali such as lime. The white powder is used in small amounts in food.

Why it’s in food

  • Raises pH gently
  • Adds a little magnesium
  • Used as a processing aid in food

Often found in

Processed foodsSome mineral supplements

Also listed as: E528, Magnesium hydrate

Health & gut impact

Laxative effect at high dosesUnder study

Large amounts of magnesium act as a laxative. Food levels are small, but people with kidney disease should check extra magnesium from supplements and antacids.

JECFA evaluation of magnesium salts

What can I use instead?

Magnesium carbonate (E504)

Ratio: A milder mineral base with similar magnesium

Best for: Anticaking and processing

Calcium carbonate (E170)

Ratio: A calcium source with a milder pH effect

Best for: Calcium-fortified foods

Related

More acidity regulators:

Acetic acid E260Acetic acid (E260) is the acid that makes vinegar sour. Diluted in food it is considered safe. The hazard is the concentrated factory form, not a splash of vinegar.Generally safeAmmonium carbonate E503Ammonium carbonate (E503) is a traditional leavening agent that makes thin cookies and crackers crisp. It breaks down into gas in the oven, so little of it stays in the finished food.Generally safeCalcium acetate E263Calcium acetate (E263) is a calcium salt of acetic acid that steadies acidity and adds a mild tang in processed foods. It is vegan and gluten-free, and it is also a prescription phosphate binder at much higher doses.Generally safeCalcium carbonate E170Calcium carbonate (E170) is ground limestone, the same calcium found in antacids. It adds calcium to plant milks and flour and is very safe.Generally safe

Common questions

Is magnesium hydroxide the same as the antacid?

Chemically yes, but food-grade material is used in much smaller amounts and is not a medicine dose.

Why does it have a laxative effect?

Magnesium is poorly absorbed in large amounts, and it draws water into the gut.

Is Magnesium hydroxide safe?

Generally safe (88/100). Permitted in the US, EU and Canada as a pH control agent and mineral source in food processing.

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Scientific sources & regulatory citations
  • EFSA OpenFoodTox: E528
  • JECFA evaluation of magnesium salts

INS 528 · CAS 1309-42-8