About
What it is and where it shows up.
Potassium metabisulfite (K₂S₂O₅) is an inorganic sulfite salt that releases sulfur dioxide (SO₂) in solution, acting as both a preservative and antioxidant. It is widely used in wine, dried fruits, juices, and packaged foods to inhibit microbial growth, prevent enzymatic browning, and extend shelf life.
Safety summary
The regulatory and scientific consensus.
A group ADI of 0–0.7 mg SO₂ equivalents/kg body weight per day is established by both JECFA and EFSA; a 2022 EFSA follow-up found that dietary exposures at maximum permitted levels produce margins of exposure (MOEs) below 80, raising safety concerns across all population groups. Sulfites can provoke allergic-type reactions—including anaphylaxis and severe asthmatic episodes—in sensitive individuals, with a reported prevalence of 3–10% among asthmatics. IARC has classified potassium metabisulfite as Group 3 (not classifiable as to carcinogenicity in humans).
Regulatory landscape
What food-safety regulators have decided.
| Jurisdiction | Status | Note |
|---|---|---|
| Food Standards Agency (FSA) / Food Standards Scotland (FSS) (United Kingdom) | Approved | Permitted under assimilated Regulation (EC) No 1333/2008 as retained in GB law post-Brexit; subject to same conditions of use as EU Annex II and Annex III.source |
| FDA (Food and Drug Administration) (United States) | Approved | Classified GRAS under the 1958 Food Additives Amendment (21 CFR Part 182). Mandatory labeling required when sulfiting agents are present at ≥10 ppm in the finished food product (21 CFR 101.100). Use on fresh fruits and vegetables sold raw to consumers is prohibited following FDA's 1986 regulatory action.source |
| EFSA (European Food Safety Authority) (European Union) | Under_review | 2022 follow-up opinion concluded MOEs below 80 raise safety concerns for high consumers at maximum permitted levels. EU specifications for arsenic, lead, and mercury should be lowered and a maximum cadmium limit introduced. Temporary ADI remains in place pending new industry data.source |
Who should approach with care
Whose guidance would steer them away.
Sulfite Sensitivity — Sulfite exposure can trigger life-threatening anaphylactic reactions, urticaria, hypotension, and severe asthmatic episodes in sulfite-sensitive individuals, as confirmed by FDA alerts and clinical literature.
Other — Steroid-dependent asthmatics and those with marked airway hyperresponsiveness are at particularly high risk of dose-dependent bronchospasm and fatal asthmatic episodes from sulfite ingestion, per peer-reviewed clinical evidence.
Children — Children with chronic asthma appear to be at greater risk of severe reactions from sulfite exposure, and EFSA 2022 found that estimated dietary exposures at maximum permitted levels raise safety concerns across all population groups including children.
Ibs — Sulfites inhibit beneficial gut bacteria (e.g., Lactobacillus and Bifidobacterium species) at food-safe concentrations, potentially exacerbating gut dysbiosis and gastrointestinal symptoms in individuals with irritable bowel syndrome.
Ibd — Suppression of beneficial gut microbiota by food-safe concentrations of sulfites may worsen gut dysbiosis, a key factor in inflammatory bowel disease pathophysiology.
Research citations
The sources behind this verdict.
- 1WHO. JECFA Food Additives Contaminants Database: Potassium metabisulfite (INS 224, CAS 16731-55-8). apps.who.int
- 2PubMed. Adverse reactions to the sulphite additives. pmc.ncbi.nlm.nih.gov
- 3PubMed. Sulfites inhibit the growth of four species of beneficial gut bacteria at concentrations regarded as safe for food. pmc.ncbi.nlm.nih.gov
- 4EFSA. Follow-up of the re-evaluation of sulfur dioxide (E 220), sodium sulfite (E 221), sodium bisulfite (E 222), sodium metabisulfite (E 223), potassium metabisulfite (E 224), calcium sulfite (E 226), calcium bisulfite (E 227) and potassium bisulfite (E 228), 2022. efsa.europa.eu
- 5PubMed. Follow-up of the re-evaluation of sulfur dioxide (E 220) ... potassium metabisulfite (E 224) ... (EFSA FAF Panel, 2022), 2022. pubmed.ncbi.nlm.nih.gov
- 6EFSA. Scientific Opinion on the re-evaluation of sulfur dioxide (E 220), sodium sulfite (E 221), sodium bisulfite (E 222), sodium metabisulfite (E 223), potassium metabisulfite (E 224), calcium sulfite (E 226), calcium bisulfite (E 227) and potassium bisulfite (E 228) as food additives, 2016.
Independently researched6 citations