Potassium nitrite
A salt used to preserve cured and processed meats, stop harmful bacteria growing, and give them their pink colour.
Regular consumption of processed meats preserved with nitrites is linked to bowel cancer and stomach cancer. Nitrites react with meat proteins to form N-nitroso compounds, which are carcinogenic. At very high doses, nitrites reduce blood's ability to carry oxygen.
What is it?
Potassium nitrite is the potassium salt of nitrous acid (KNO2). It is a white or slightly yellowish solid that dissolves easily in water. It functions as a curing salt, most often used alongside or instead of sodium nitrite (E250), and at lower use levels than its sodium counterpart.
What does it do?
Nitrite ions released from potassium nitrite bind to the myoglobin in meat, producing the stable pink or red colour associated with cured products. More importantly, nitrite suppresses the growth of Clostridium botulinum, the bacterium responsible for botulism, making it a critical food-safety tool in processed meats. Nitrite also inhibits lipid oxidation, slowing rancidity and contributing to the characteristic flavour of cured meats.
Where you will see it
Used in cured and processed meat products including bacon, ham, salami, chorizo, frankfurters, luncheon meat, pate, and other charcuterie. Also permitted in certain traditional cured products with specific preparation rules. On UK labels it appears as 'potassium nitrite' or 'E249', usually within the preservatives declaration in the ingredients list.
What the science says
Processed meat and bowel cancer
IARC classified processed meat as a Group 1 carcinogen in 2015, meaning the evidence that it causes cancer in humans is sufficient. Nitrites are considered a key contributing factor because they react with proteins in meat during curing and cooking to form N-nitroso compounds (NOCs), several of which are established animal carcinogens. The IARC conclusion covers consumption of processed meat generally, not isolated nitrite exposure.
IARC classified processed meat as Group 1 (causes cancer in humans), with colorectal cancer as the primary outcome; nitrite-derived N-nitroso compound formation in meat was identified as a plausible mechanism.
The EFSA ANS Panel found 'some evidence' linking dietary nitrite intake to gastric cancer and 'evidence' connecting preformed NDMA in processed meat to colorectal cancer risk.
N-nitroso compound formation
When nitrites are present in meat alongside proteins containing secondary amines, N-nitroso compounds including nitrosamines can form, particularly during high-heat cooking such as frying bacon. Several nitrosamines are classified as probable or possible human carcinogens. The extent of formation depends on nitrite concentration, protein content, temperature, and pH.
Cooking nitrite-preserved meat at high temperatures substantially increases the yield of volatile nitrosamines, particularly N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine.
At high dietary exposure levels the margin of exposure for exogenous nitrosamines in meat products may fall below 10,000, which EFSA considers a level of potential concern.
Methaemoglobinaemia (blood oxygen impairment)
Nitrite directly oxidises haemoglobin to methaemoglobin, a form that cannot carry oxygen. At the doses used in permitted food applications, healthy adults metabolise nitrite rapidly enough that blood levels do not reach harmful thresholds. However, infants under six months are at higher risk because their methaemoglobin-reducing enzyme is not yet fully active, and very high acute exposures are dangerous at any age. EFSA set its ADI specifically based on the dose at which methaemoglobin formation becomes measurable in animal studies.
EFSA established an ADI of 0.07 mg nitrite ion per kg bodyweight per day, derived from a benchmark dose modelling approach using methaemoglobin formation in rats as the critical endpoint.
Children at high dietary exposure percentiles may exceed the ADI for nitrite from food additive sources alone; combined exposure from all dietary sources (additives plus naturally occurring nitrate/nitrite in vegetables) raised additional concern.
Food safety role: botulism prevention
The continued approval of nitrites in cured meat rests substantially on their effectiveness against Clostridium botulinum, which produces one of the most potent toxins known. Regulators weigh the cancer-risk signal from processed meat against the serious food-poisoning risk that would increase if nitrite preservatives were removed without an equivalent replacement. Several food safety agencies have noted this trade-off explicitly.
Nitrite inhibits outgrowth of Clostridium botulinum spores in cured meat; EFSA and FSA reviews have noted that this food-safety function must be considered alongside the toxicological concerns when evaluating permitted levels.
Where it stands with the regulators
Who should be careful
Infants under six months should not be given nitrite-preserved meats. People who eat processed meat daily face the highest cumulative exposure: reducing intake of bacon, ham, salami, and other cured products reduces both nitrite exposure and the broader processed-meat cancer risk. Look for 'potassium nitrite', 'sodium nitrite', 'E249', or 'E250' in the ingredients list of cured and deli meats.
The honest read
The cancer signal here is real and comes from IARC, the body that evaluates carcinogen evidence for the WHO. The Group 1 classification for processed meat is one of the strongest IARC can assign. Nitrite is not the only component in that finding, but it is consistently identified as a key mechanism through N-nitroso compound formation. At the same time, the risk is dose-related: occasional consumption of cured meat carries a different exposure profile than daily consumption. EFSA's 2017 review did not withdraw approval partly because nitrite's role in preventing botulism is itself a genuine public health benefit. The science linking nitrites in food to cancer risk is not disputed at the level of regulatory bodies; what remains less settled is the exact dose-response relationship for nitrite alone, independent of other processed-meat components.
Related additives
Common questions
Is E249 banned in the UK?
No. E249 is approved for use in the UK as a preservative in processed and cured meat products, under the UK FSA approved-additives list and assimilated EU Regulation 1333/2008. Maximum permitted levels apply.
Why is E249 linked to cancer if it is still permitted?
IARC classified processed meat as a Group 1 carcinogen in 2015, with nitrites identified as a key contributing mechanism via N-nitroso compound formation. However, regulators have continued to permit nitrite preservatives because they also prevent botulism, a potentially fatal food-borne illness. The approval reflects a risk trade-off rather than a clean bill of health.
What foods contain E249?
E249 is used in cured and processed meats including bacon, ham, salami, chorizo, frankfurters, luncheon meat, pate, and other charcuterie. It appears on labels as 'potassium nitrite' or 'E249' in the ingredients list.
Is E249 vegan?
Potassium nitrite itself is a mineral salt with no animal origin. However, it is used almost exclusively in meat products, so encountering it in practice means the food itself is not vegan.
Sources
- EFSA ANS Panel: Re-evaluation of potassium nitrite (E 249) and sodium nitrite (E 250) as food additives
- IARC Monographs Volume 114: Red Meat and Processed Meat (2018 publication of 2015 evaluation)
- UK FSA: Approved additives and E numbers
- Harvard T.H. Chan School of Public Health: WHO report says eating processed meat is carcinogenic (2015)
- PMC: Evaluating the Residual Nitrite Concentrations of Bacon in the United Kingdom
Aaron Keen is the founder of NutraSafe. He researches and writes every additive entry himself, from the primary sources. About the research →
This is a guide, not medical advice. If an additive affects you, speak to your GP or a dietitian.
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