Sodium nitrite
A curing salt added to processed and cured meats to prevent botulism, fix the pink colour, and extend shelf life. Regular cured-meat eating is linked to bowel cancer.
Regular consumption of processed meats containing sodium nitrite is linked to colorectal cancer. Nitrite reacts with meat proteins and amino acids to form N-nitroso compounds, which are carcinogenic in animal studies. Every 50g of processed meat eaten daily is associated with approximately an 18% increase in colorectal cancer risk. At very high doses, nitrite reduces blood's ability to carry oxygen, with infants under six months especially vulnerable.
What is it?
Sodium nitrite (NaNO2) is the sodium salt of nitrous acid. It is a white to pale-yellow crystalline solid that dissolves readily in water. As a food additive it functions primarily as a curing agent and preservative in processed and cured meat products, where it is typically applied as a dilute curing salt mixture alongside sodium chloride.
What does it do?
Nitrite ions released from sodium nitrite react with the myoglobin in meat to produce stable nitrosomyoglobin, giving cured products such as bacon and ham their characteristic pink or red colour. Nitrite also inhibits the growth and toxin production of Clostridium botulinum, the bacterium responsible for botulism, making it a critical food-safety tool. Additionally, nitrite suppresses fat oxidation, slowing rancidity and contributing to the distinctive flavour of cured meats. At the concentrations used in food, nitrite is rapidly metabolised in healthy adults, but it can form N-nitroso compounds when it reacts with secondary amines or amides in meat, particularly during high-heat cooking.
Where you will see it
Bacon, ham, salami, chorizo, frankfurters, luncheon meat, corned beef, pate, and other cured or processed meats. Also used alongside E249 (potassium nitrite) in some curing blends. On UK labels it appears as 'sodium nitrite', 'E250', or within a declaration of 'curing salts', typically in the preservatives section of the ingredients list.
What the science says
Processed meat and colorectal cancer: IARC Group 1
In 2015, the International Agency for Research on Cancer (IARC) classified the consumption of processed meat as a Group 1 carcinogen, meaning there is sufficient evidence it causes colorectal cancer in humans. The classification covers the food category, not any single additive in isolation. Based on an analysis of 10 epidemiological studies, IARC found that every 50g of processed meat eaten daily was associated with approximately an 18% increase in colorectal cancer risk. The WCRF Continuous Update Project analysis of nine cohort studies produced the same figure. Nitrites are identified as a key contributing mechanism through the formation of N-nitroso compounds in meat and in the gut.
IARC Working Group classified processed meat as Group 1 carcinogenic to humans, with colorectal cancer as the primary site. An analysis of 10 studies found that every 50g portion of processed meat eaten daily was associated with approximately an 18% increase in colorectal cancer risk.
WCRF Continuous Update Project analysis of nine cohort studies found strong evidence that eating processed meat increases the risk of bowel cancer by 18% per 50g processed meat per day (RR 1.18, 95% CI 1.10-1.28).
The EFSA ANS Panel found evidence linking dietary nitrite intake to gastric cancer and evidence connecting preformed N-nitrosodimethylamine (NDMA) in processed meat to colorectal cancer risk.
N-nitroso compound formation
Sodium nitrite reacts with secondary amines and amides present in meat proteins to form N-nitroso compounds (NOCs), including nitrosamines. This can occur during curing, cooking, and digestion. Several nitrosamines are established animal carcinogens, and some are classified as probable or possible human carcinogens. High-heat cooking of nitrite-cured meat, such as frying bacon, substantially increases the yield of volatile nitrosamines. The haem iron in red meat also accelerates endogenous nitrosation in the gut.
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. Infants under six months are at elevated risk because their methaemoglobin-reducing enzyme is not yet fully active and foetal haemoglobin is more readily oxidised. 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 benchmark dose modelling 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 sodium nitrite in cured meat rests substantially on its 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. Both EFSA and the UK FSA have noted this trade-off explicitly in their reviews.
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 carry 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 'sodium nitrite', 'E250', or 'curing salts' 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. Sodium nitrite is not the sole component in that finding, but it is consistently identified as a key mechanism through N-nitroso compound formation. The risk is dose-related: regular daily consumption of cured meat carries a meaningfully different exposure profile than occasional intake. 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 in dispute among regulatory bodies; what remains less settled is the precise dose-response relationship for nitrite alone, independent of other processed-meat components.
Related additives
Common questions
Is E250 banned in the UK?
No. Sodium nitrite (E250) 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 and it is not approved for use in other food categories.
Why is E250 linked to cancer if it is still permitted?
IARC classified processed meat as a Group 1 carcinogen in 2015, with sodium nitrite 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, not an absence of concern.
What is the difference between E250 and E249?
E250 is sodium nitrite and E249 is potassium nitrite. Both supply nitrite ions and perform the same curing, colour-fixing, and antimicrobial functions. E249 is used where lower sodium content is a formulation goal. Their toxicological profiles are effectively identical and EFSA evaluated them jointly in 2017.
What foods contain E250?
Bacon, ham, salami, chorizo, frankfurters, luncheon meat, corned beef, pate, and other cured or processed meats are the primary sources. It appears on labels as 'sodium nitrite' or 'E250', typically in the preservatives section of the ingredients list.
Is E250 vegan?
Sodium 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
- IARC Press Release No. 240: IARC Monographs evaluate consumption of red meat and processed meat (October 2015)
- Bouvard et al., Carcinogenicity of consumption of red and processed meat, Lancet Oncology, 2015
- IARC Monographs Volume 114: Red Meat and Processed Meat (2018 publication of 2015 evaluation)
- WHO Q&A: Carcinogenicity of consumption of red meat and processed meat
- WCRF: Red meat and bowel cancer risk - how strong is the evidence?
- EFSA ANS Panel: Re-evaluation of potassium nitrite (E 249) and sodium nitrite (E 250) as food additives, EFSA Journal 2017
- EFSA ANS Panel re-evaluation of E249 and E250 (PMC version of record)
- UK FSA: Approved additives and E numbers
- UK FSA: Nitrates and nitrites - the science explained
- NHS: Meat in your diet (red and processed meat guidance)
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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