Sodium nitrate
A curing salt used in long-cured ham, salami and chorizo. It turns into nitrite. Processed meat causes bowel cancer, and nitrite is one of the reasons.
How common it is in UK food
UK supermarket foods declare E251 in their ingredients, by its code or its name. That is 0.7% of the 43,325 food products we hold an ingredient list for.
Where it turns up most
- Fresh meat, poultry and fish123 products2.5% of 4,835 in this aisle
- Cooked and cured meats91 products4.7% of 1,938 in this aisle
- Ready meals and pizza30 products0.6% of 4,833 in this aisle
- Bread and bakery17 products0.5% of 3,682 in this aisle
Only 1.8% of these labels print “E251”. Most use the name: look for “sodium nitrate”.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
Scan a barcode to check a food for sodium nitrate.
We name each additive in the ingredients and say what it does, with the source.
Nitrate turns into nitrite in the body, which can form N-nitroso compounds linked to bowel cancer. The WHO's cancer agency classes regular processed meat eating as a cause of bowel cancer.
What is it?
Sodium nitrate is the sodium salt of nitric acid, a white crystalline solid found naturally in soil and some vegetables. In food it is a curing salt: a store of nitrate that bacteria slowly turn into nitrite as meat cures.
What does it do?
During curing, bacteria gradually turn sodium nitrate into sodium nitrite (E250). The nitrite reacts with the red pigment in meat to give bacon, ham and salami their lasting pink colour. It also stops the growth of the bacterium that causes botulism and slows fat going rancid. Because it releases nitrite slowly, it suits meat that cures for a long time.
Where you will see it
Cured hams, dry-cured and fermented meats such as salami and chorizo, long-aged bacon and some cured fish. It is also allowed on the rind of some cheeses. UK labels call it sodium nitrate, E251 or curing salt, sometimes alongside E250 (sodium nitrite).
What the science says
Processed meat causes bowel cancer
In 2015 IARC, the WHO's cancer agency, classed processed meat as causing bowel cancer in humans (Group 1). The classification is for the food, not a single additive, but added nitrate and nitrite are part of how it may happen, because they can form N-nitroso compounds in the gut. Every 50g of processed meat a day was linked to about 18% higher risk. For more on cured meat, see our page on sodium nitrite (E250).
IARC classed processed meat as causing cancer in humans (Group 1), mainly bowel cancer. Every 50g of processed meat eaten a day was linked to about an 18% higher risk.
IARC classed ingested nitrate as probably causing cancer in humans (Group 2A) when it leads to N-nitroso compounds forming in the body.
How nitrate may lead to cancer
When nitrite from nitrate meets parts of protein in the acidic stomach and in the bowel, it can form N-nitroso compounds, many of which cause cancer in animals. Haem iron, the iron in red meat, speeds this up. The evidence points to the combination of processed meat, nitrate or nitrite and haem, rather than any one part alone.
Haem iron in red and processed meat speeds up the formation of N-nitroso compounds in the gut, a plausible link between processed meat and bowel cancer.
On its own, nitrate shows little or no cancer effect in animal studies. The cancer signal appears when it is turned into nitrite and then N-nitroso compounds in the body.
How much processed meat the NHS advises
The NHS advises that people who eat more than 90g of red and processed meat a day cut down to 70g. The advice covers all processed meat, not only meat with nitrate, but nitrate-cured meat is the main category it applies to.
The NHS advises eating no more than 70g of red and processed meat a day, and cutting down if you eat more, because of the link with bowel cancer found in population studies.
Babies and blue baby syndrome
A lot of nitrate can turn haemoglobin into a form that cannot carry oxygen well. Babies under six months are most at risk. This has mainly been linked to well water high in nitrate, not food additives at permitted levels, but it is one reason limits are strict.
High doses of nitrate cause methaemoglobinaemia in babies, reducing how well blood carries oxygen. Maximum levels in food are set partly to protect them.
The 2017 European review
European reviewers looked at nitrates and nitrites as additives in 2017 and kept a daily limit for nitrate of 3.7mg per kg of body weight. They found intake from additives alone was within it, but that nitrate from all sources, including vegetables and water, could go over it in people who eat the most, children included.
Reviewers kept a daily limit of 3.7mg of nitrate per kg of body weight. Intake from additives alone was within it, but total nitrate from all food sources could go over it in high-intake groups.
Where it stands with the regulators
Who should be careful
People who eat processed meat often, particularly every day, have the highest total exposure. Babies under six months should not have foods with added nitrate. People with conditions affecting how blood carries oxygen should talk to their doctor about cured meat. Look for sodium nitrate, E251 or curing salt.
The honest read
At the additive level, sodium nitrate is approved and its limits are set below what European reviewers consider harmful for most adults. At the diet level, IARC's classification of processed meat as causing cancer is one of the more solid findings in nutrition research, backed by large pooled studies from many countries. The explanation, nitrite, haem iron and protein forming N-nitroso compounds in the gut, is biologically plausible and seen in lab and animal work. But people eat the whole product, nitrate plus haem plus salt plus cooking chemistry, so it is not possible to isolate sodium nitrate's own share of the risk from current data. Whether lower limits or other preservatives would cut population risk is still being researched.
Related additives
Common questions
Is E251 banned in the UK?
No. Sodium nitrate is approved in the UK in specific foods, including cured and processed meat, up to set limits.
Does sodium nitrate cause cancer?
IARC classes ingested nitrate as probably causing cancer in humans (Group 2A) when it leads to N-nitroso compounds forming in the body. Processed meat, the food it is mostly used in, is classed as causing bowel cancer (Group 1). Current studies cannot separate sodium nitrate's share from the rest of processed meat.
What foods contain E251?
Mainly cured and fermented meat: dry-cured ham, salami, chorizo, pepperoni, long-cured bacon and some cured fish. It may also be on the rind of some hard cheeses. Look for sodium nitrate or E251.
Is E251 vegan?
The salt is a mineral, not from animals. But it is used almost only in cured meat and fish, so the foods it is in are not vegan.
Sources
- IARC Monographs Volume 114: Red Meat and Processed Meat (2018 update of 2015 findings)
- Bouvard et al., Carcinogenicity of consumption of red and processed meat, Lancet Oncology
- IARC Monographs Volume 94: Ingested Nitrate and Nitrite, and Cyanobacterial Peptide Toxins
- EFSA ANS Panel, Re-evaluation of sodium and potassium nitrites and nitrates as food additives, EFSA Journal
- UK Food Standards Agency: Nitrates and Nitrites - The Science Explained
- UK Food Standards Agency: Approved Additives and E Numbers
- NHS: Red meat and bowel cancer
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