Potassium nitrate
A curing salt used mainly in cured and processed meats to prevent botulism and keep meat red. Converts to nitrite during curing.
Regular consumption of processed and cured meats is linked to bowel cancer. Nitrite formed from potassium nitrate reacts with meat proteins to produce nitrosamines, compounds classed as probable or known carcinogens. IARC classifies processed meat as a Group 1 carcinogen.
What is it?
Potassium nitrate (saltpetre) is an inorganic salt. As a food additive it is the potassium counterpart of sodium nitrate (E251) and belongs to the nitrate family of curing agents. It does not itself preserve meat directly; it acts as a reservoir that is gradually converted to nitrite by bacteria naturally present in the meat during curing.
What does it do?
In cured meats, bacteria reduce potassium nitrate to nitrite over the course of slow curing. The nitrite then binds myoglobin (producing the characteristic pink colour), inhibits the growth of Clostridium botulinum (the bacterium behind botulism), and retards fat oxidation. This two-step conversion makes potassium nitrate better suited to long-cured products such as dry-cured ham than to quick-cured products, where fast-acting sodium nitrite (E250) is preferred.
Where you will see it
Used mainly in traditional or slow-cured meat products, including dry-cured ham, some salamis, hard sausages, and certain cured cheeses. It may also appear in some cured fish. On a UK label it appears as potassium nitrate or E252.
What the science says
Processed meat and bowel cancer: the IARC finding
IARC (the WHO cancer agency) classified processed meat as a Group 1 carcinogen in 2015, meaning there is sufficient evidence from human studies that it causes colorectal cancer. The classification is based partly on the formation of N-nitroso compounds (nitrosamines and nitrosamides) when nitrite reacts with proteins in the gut. Consuming 50g of processed meat a day is associated with an approximately 18% higher risk of colorectal cancer.
IARC classified processed meat as Group 1 carcinogenic to humans, citing sufficient evidence from epidemiological studies for colorectal cancer; nitrite-derived N-nitroso compounds are one of the mechanistic explanations.
A WCRF Continuous Update Project meta-analysis estimated a 12% increase in colorectal cancer risk for each 100g per day increment in processed meat consumption.
Nitrite and nitrosamine formation
Potassium nitrate is reduced to nitrite during curing. Nitrite reacts with amines from meat proteins under acidic conditions (such as in the stomach) to form N-nitroso compounds, including nitrosamines. Several nitrosamines formed this way are classed by IARC as Group 2A (probable human carcinogens). The conversion is higher when meat is cooked at high temperatures.
N-nitrosodimethylamine (NDMA) and several related nitrosamines formed from nitrite-treated meat are classified as Group 2A probable human carcinogens.
A review of in vivo evidence found consistent association between nitrite from processed meat and colorectal carcinogenesis, with N-nitroso compound formation identified as a plausible biological pathway.
EFSA re-evaluation and ADI
EFSA completed a full re-evaluation of sodium and potassium nitrate in 2017. It retained their permitted uses but tightened its acceptable daily intake for nitrate from all food additive sources combined and noted that typical dietary exposure to added nitrates, combined with dietary nitrates from vegetables, can exceed the ADI in some population groups, particularly children. The FSA commissioned a further rapid evidence review published after 2024.
EFSA's 2017 re-evaluation set an ADI for nitrate from food additives of 3.7mg/kg body weight per day and concluded that added nitrates remain permitted at current levels, but flagged that combined additive plus vegetable-source nitrate intake can exceed the ADI in high-consuming subgroups.
Botulism prevention: the food safety trade-off
Regulatory agencies maintain that the use of nitrate and nitrite in cured meats is justified on food safety grounds because the alternative, cured meat without nitrite, carries a real risk of Clostridium botulinum growth and botulism poisoning. This is the core reason the additive remains approved despite the cancer signal.
FSA guidance states that nitrites and nitrates in meat products are maintained at the lowest effective levels because of their established role in preventing botulism, and that regulators are keeping permitted levels under review.
Where it stands with the regulators
Who should be careful
Anyone limiting processed meat intake for bowel cancer risk should look for potassium nitrate, potassium nitrite, sodium nitrate, sodium nitrite, E252, E251, E250 or E249 on cured meat labels. People with low body weight, children, and anyone already near the top of their nitrate intake from vegetables and water should pay attention to how often they eat cured meats that carry these additives.
The honest read
The link between processed meat and bowel cancer is one of the most consistent findings in nutritional epidemiology. The IARC Group 1 classification reflects decades of human data, not animal studies alone. The specific role of added nitrate and nitrite versus other factors in cured meat (haem iron, cooking compounds, fat content) is still being separated out, so attributing a precise share of the cancer signal to E252 alone is not possible yet. Regulators keep the additive approved because it prevents a real and serious risk, botulism, but they are also asking industry to reduce levels. The science here is active and the regulatory picture is shifting.
Related additives
Common questions
Is E252 banned in the UK?
No. Potassium nitrate (E252) is approved for use in the UK and EU in certain cured meat, cheese and fish products. Its use is tightly restricted to specific food categories and maximum permitted levels.
Does E252 cause cancer?
E252 itself is not directly classified as a carcinogen, but during curing it is converted to nitrite, which can form nitrosamines in the meat and in the gut. IARC classifies processed meat as a Group 1 carcinogen (causes bowel cancer in humans), and nitrite-derived N-nitroso compounds are one of the likely contributing mechanisms. The additive is not banned because it also prevents botulism, which is also life-threatening.
What foods contain E252?
Mainly dry-cured and traditionally slow-cured meat products, such as dry-cured ham, some hard sausages and salamis. It may also appear in certain cured cheeses and cured fish. Look for potassium nitrate or E252 in the ingredients list.
Is E252 vegan?
Potassium nitrate as a chemical compound is not derived from animals. However, it is used almost exclusively in meat and fish products, so the end product is not vegan. It is suitable for vegetarians and vegans as an isolated ingredient, but the foods it is added to typically are not.
Sources
- UK FSA: E252 potassium nitrate regulated product entry
- UK FSA: Approved additives and E numbers
- EFSA Journal: Re-evaluation of sodium nitrate (E251) and potassium nitrate (E252) as food additives (2017)
- EFSA press release: EFSA confirms safe levels for nitrites and nitrates added to food (2017)
- IARC Monographs Volume 114: Red meat and processed meat (2015)
- FSA Research: Safety of nitrates and nitrites as food additives
- Gilchrist et al.: A Review of In Vivo Evidence Investigating Nitrite Exposure from Processed Meat in Colorectal Cancer Development, Nutrients (PMC6893523)
- World Cancer Research Fund International: Continuous Update Project, Diet, Nutrition, Physical Activity and Colorectal Cancer
- European Commission: Call for technical data on E249-E252 (2022)
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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