Magnesium Hydroxide

About

What it is and where it shows up.

Magnesium hydroxide is an inorganic mineral compound used in food as an acidity regulator, pH-control agent, color-retention agent, and nutritional supplement providing dietary magnesium. It is also used as an alkali drying agent, a clarifier in sugar refining, and an ingredient in frozen desserts.

Safety summary

The regulatory and scientific consensus.

Magnesium hydroxide is FDA-affirmed GRAS and EU-approved as E528 with no numeric ADI restriction for the general adult population, and no carcinogenicity or genotoxicity concerns have been identified at typical food-additive intake levels. At high (laxative) doses it can cause osmotic diarrhea due to unabsorbed magnesium ions in the gut. Individuals with impaired kidney function are at risk of hypermagnesemia, as urinary excretion accounts for 80–90% of absorbed magnesium under normal renal function.

Regulatory landscape

What food-safety regulators have decided.

Jurisdiction	Status	Note
EFSA (European Food Safety Authority) (European Union)	Approved	Approved food additive E528 under Regulation (EC) No 1333/2008 with specifications laid down in Commission Regulation (EU) No 231/2012; permitted as acidity regulator and color retention agent at quantum satis (GMP); separately approved as basic substance for plant protection use via Commission Implementing Regulation (EU) 2024/836 of 12 March 2024source
FDA (Food and Drug Administration) (United States)	Approved	Affirmed GRAS under 21 CFR 184.1431 as a direct food substance; approved as a nutritional supplement and pH-control agent; GMP limits apply; regulation amended January 5, 1999 (64 FR 404–405)source

Who should approach with care

Whose guidance would steer them away.

Kidney Disease — Urinary excretion accounts for 80–90% of absorbed magnesium under normal renal function; impaired kidney function prevents adequate clearance of absorbed Mg²⁺, creating risk of hypermagnesemia which can cause refractory hypotension, respiratory depression, and coma.

Infants — Case reports document hypermagnesemia in newborns following antacid administration containing magnesium hydroxide, reflecting immature renal handling of magnesium in this population.

Research citations

The sources behind this verdict.

1other. Magnesium Hydroxide — Toxicological Risks of Selected Flame-Retardant Chemicals (NCBI Bookshelf, National Academies). ncbi.nlm.nih.gov
2WHO. JECFA Food Additive Detail: Magnesium Hydroxide (INS 528). fao.org
3other. Commission Implementing Regulation (EU) 2024/836 of 12 March 2024 Approving the Basic Substance Magnesium Hydroxide E528, 2024. eur-lex.europa.eu
4EFSA. Outcome of the Consultation with Member States and EFSA on the Basic Substance Application for Approval of Magnesium Hydroxide E528, 2023. efsa.europa.eu
5FDA. Direct Food Substances Affirmed as Generally Recognized as Safe; Magnesium Hydroxide — 21 CFR Part 184.1431, 1985. accessdata.fda.gov

Independently researched5 citations