What is E251?
Complete guide to understanding E251 (Sodium Nitrate) — a naturally-occurring preservative used in long-ripened meats with significant cancer concerns
The Quick Answer
E251 (Sodium Nitrate) is a naturally-occurring preservative and color fixative used primarily in long-ripened and dry-cured meats (ham, salami, fermented sausages).
It works by slowly converting to nitrites during the curing and ripening process, providing gradual preservation over weeks or months of aging.
Like E249/E250 (nitrites), it’s approved but increasingly controversial due to epidemiological links with colorectal cancer through nitrosamine formation. Its “natural” origin provides no safety advantage over synthetic nitrates.
📌 Quick Facts
- Chemical Name: Sodium Nitrate (Chile saltpetre/Peru saltpetre; naturally-occurring mineral)
- Type: Preservative and color retention agent; antimicrobial and antioxidant
- Found in: Long-ripened cured meats, dry-cured ham, fermented sausages, traditional cheese
- Safety Status: Approved by EFSA, FDA, JECFA; but EFSA 2023 says nitrosamine exposure is “concerning”
- Approved by: EU, US, Australia, New Zealand, Canada, WHO/JECFA
- Acceptable Daily Intake: 3.7 mg/kg body weight/day (much higher than nitrites, but same conversion pathway)
- Primary function: Slow-release preservation; converts to nitrite during ripening
- Main concern: Converts to carcinogenic nitrosamines; epidemiological cancer links
- Regulatory trend: New EU regulation (Oct 2025) reduces permitted levels
What Exactly Is It?
E251 is a white solid that is very soluble in water — sodium nitrate, a naturally-occurring mineral found in large deposits in Chile and Peru.
Unlike E249 (potassium nitrite) and E250 (sodium nitrite), E251 is a naturally-occurring mineral, though it’s also produced synthetically. However, chemically identical substances have identical biological effects regardless of origin.
Chemical formula: NaNO₃ — sodium, nitrogen, and oxygen.
Key properties:
– Highly soluble in water
– Slowly converts to nitrite during curing (unlike immediate nitrites)
– Acts as “reservoir” for gradual nitrite release during ripening
– Reacts with proteins/amines to form nitrosamines (potential carcinogens)
– Develops and fixes the pink/red color of cured meats
– Contributes to characteristic cured meat flavor
– Better for long-ripening products than quick-acting nitrites
Where You’ll Find It
E251 is found primarily in traditional long-ripened and dry-cured meat products:
| Product Category | Specific Examples | Why E251 (not E250)? |
|---|---|---|
| Dry-Cured Ham | Traditional dry-cured ham (Parma ham, Prosciutto, Jamón), aged ham products | Weeks-to-months ripening; slow nitrate→nitrite conversion needed |
| Fermented Sausages | Salami, pepperoni, fermented dried sausages | Long fermentation; bacterial action converts nitrate to nitrite |
| Other Cured Products | Bacon (some formulations), cured meats, traditional preparations | Can be used alone or with nitrites for dual preservation |
| Ripened Cheeses | Some traditional cheese varieties (limited use) | Antimicrobial during aging |
| Dairy Cheese Products | Cheese-containing foods (limited use) | Secondary preservation function |
| Pickled Herring | Traditional pickled fish products | Preservation in acidic/brining environment |
EU permitted levels (changing October 2025): Varies significantly by product type; traditional products typically 150-500 mg/kg ingoing amount, with lower residual limits after curing.
Why Is E251 Used? The Slow-Release Preservation Strategy
E251’s unique function: slow-release preservation for long-ripening products.
Critical function for specific products:
– Long-ripening preservation: Nitrates slowly convert to nitrites over weeks/months of aging
– Gradual antimicrobial effect: Provides sustained protection throughout aging process
– Traditional authenticity: Essential for traditional dry-cured ham, fermented sausages
– Traditional product enabler: Without E251 (or E252), traditional aged products would require short shelf life or refrigeration
– Cannot use nitrites alone: Fast-acting nitrites (E249/E250) would be consumed/degraded during long aging; wouldn’t provide sustained preservation
Secondary functions:
– Maintains pink/red color through nitrite formation and myoglobin reaction
– Develops characteristic flavor of traditional cured meats
– Cost-effective preservation method
– Enables traditional production without modern refrigeration
E251 vs. E250: Understanding the Difference
The nitrite/nitrate distinction is critical:
| Property | E250 (Sodium Nitrite) | E251 (Sodium Nitrate) |
|---|---|---|
| Chemical form | Nitrite (NO₂⁻); immediate | Nitrate (NO₃⁻); converts slowly |
| Speed of action | Fast-acting (hours) | Slow-acting (days/weeks) |
| Best for | Quick curing, heat-treated meats, bacon | Long ripening, traditional aged products |
| ADI | 0.07 mg/kg (very restrictive) | 3.7 mg/kg (more permissive but same outcome) |
| Mechanism | Immediate NO release | Bacterial/chemical conversion to NO |
| Nitrosamine formation | Rapid (hours/cooking) | Delayed (during ripening + digestion) |
| Regulatory concern | Highest concern due to immediate formation | High concern due to inevitable conversion |
Is It Safe? The Concerning Answer
The Official Position
E251 is approved by EFSA, FDA, and JECFA, BUT with increasing regulatory concern.
| Authority | Position | ADI | Status |
|---|---|---|---|
| EFSA (2023 rapid review) | Approved; BUT “nitrosamine exposure concerning” | Not changed; same as before | Concern acknowledged; levels being reduced |
| JECFA (WHO) | Approved | 3.7 mg/kg bw/day | Since ~1990s |
| FDA (US) | Approved | Not specified numerically | Ongoing; less strict than EU |
| EU (new regulation 2024/1146) | Approved with REDUCED limits | 3.7 mg/kg (same) but lower max permitted | October 2025 implementation; tightening |
For a 70 kg adult: The ADI of 3.7 mg/kg means approximately 259 mg per day is “safe” — much less restrictive than E249/E250 (4.9 mg/day), but the end biological pathway is identical.
EFSA’s 2023 Finding: Concerning Nitrosamine Exposure
This doesn’t mean E251 is being banned, but it indicates regulatory concern is increasing. New EU regulations (October 2025) reduce permitted levels as a precautionary measure.
Why this matters:
– EFSA acknowledges that current nitrosamine exposure from nitrite/nitrate additives in food is “concerning”
– Despite this concern, approval is maintained because alternatives would compromise food safety or be infeasible
– Response: Reduce permitted levels while maintaining essential preservation function
– Reflects regulatory shift from “safe at permitted levels” to “reducing exposure because concerning”
The Inevitable Nitrosamine Formation Pathway
Unlike nitrites (E249/E250), nitrate conversion is slower, but inevitable:
During ripening:
– Bacteria in fermented products convert nitrate → nitrite
– Enzymes and acidic conditions reduce nitrate → nitrite
– Nitrite then reacts with proteins → N-nitrosamines form
During digestion:
– Stomach acid converts remaining nitrate → nitrite
– Nitrite reacts with dietary amines → N-nitrosamines form in gastrointestinal tract
Critical point: The ADI for nitrate is much higher (3.7 mg/kg vs. 0.07 mg/kg), but this reflects slower conversion rate, not safety advantage. The end product—N-nitrosamines—is identical and carcinogenic regardless.
Epidemiological Evidence (Suggestive but Not Proven)
What population studies suggest:
– Colorectal cancer: Strong associations with processed meat consumption (which contains nitrate + nitrite)
– Gastric/oesophageal cancer: Some associations with high nitrate intake
– Cardiovascular disease: Meta-analysis linked high processed meat consumption to cardiovascular death
– Neurodegenerative disease: Some evidence linking high dietary nitrate to Alzheimer’s, Parkinson’s through nitrosamine-mediated DNA damage
Important limitations:
– Processed meat contains many harmful compounds beyond nitrates
– Confounders: salt, fat, smoking/cooking methods, genetics
– Causation not established; associations are suggestive only
– Cannot clearly isolate E251 effect from overall processed meat consumption
Important Context: Natural Dietary Nitrates
Food additive nitrates (E251) contribute only PART of total dietary nitrate exposure:
– Vegetables: Spinach, lettuce, beets, cabbage, celery — major source (>500 mg/day common)
– Food additives: Cured meats — ~50-200 mg/kg
– Drinking water: Can be significant in agricultural areas
– Saliva/endogenous: Body produces nitrate
Why this distinction matters:
– Total dietary nitrate from vegetables often exceeds additive sources
– BUT: Vegetables contain antioxidants (vitamin C, polyphenols) that may reduce nitrosamine formation
– Processed meat nitrates lack these protective compounds
– AND: Cured meat provides immediate protein source for nitrite reaction (more efficient nitrosamine formation)
The Regulatory Decision: Why Still Approved?
Despite EFSA’s 2023 acknowledgment that nitrosamine exposure is “concerning,” E251 remains approved because:
1. Botulism prevention is critical: Traditional products rely on E251 for safe preservation
2. No effective alternative exists: Other methods would eliminate traditional product category
3. Risk-benefit calculation: Regulatory judgment that some cancer risk is acceptable to prevent botulism
4. Reduction over elimination: Strategy is to reduce permitted levels (October 2025 regulation) rather than ban
The Bottom Line
E251 (Sodium Nitrate) is a naturally-occurring preservative with a specialized function for long-ripened products, but with documented cancer concerns that are increasingly recognized by regulators.
What you should know:
- It’s naturally-occurring BUT equally concerning: “Natural” origin provides no safety advantage; chemically identical to synthetic nitrate
- It’s approved but increasingly questioned: EFSA 2023 acknowledges nitrosamine exposure is “concerning for health”
- It inevitably forms carcinogens: Conversion to nitrosamines is not preventable; only avoidable through reduced consumption
- Cancer links are epidemiologically suggestive: Studies show associations; causation not proven but plausible
- Regulatory trend is restrictive: New EU regulation (Oct 2025) reduces permitted levels, reflecting growing concern
- It’s essential for traditional products: Without E251, long-ripened traditional meats would be infeasible
- Total dietary exposure matters: Vegetables contain more natural nitrate, but processed meat nitrate may be more carcinogenic
- Children particularly vulnerable: Their hemoglobin more sensitive to nitrite effects