E250

Sodium Nitrite

Last reviewed: 11 May 2026

The UK label-reader's guide to cured-meat preservative and the IARC Group 1 classification

What it is

E250 is sodium nitrite (NaNO₂), the curing salt at the centre of nearly every cured-meat ingredient list in the UK. It does three jobs at once: it inhibits the growth of Clostridium botulinum spores in the anaerobic interior of cured meat (the historic public-health driver for nitrite use), it fixes the characteristic pink colour by reacting with myoglobin to form nitrosylmyoglobin, and it produces the distinctive cured flavour. It also has a mild antioxidant effect on fats. Nitrite chemistry under cooking and digestion is the reason this single additive carries the IARC Group 1 weight described above — the molecules of concern are the N-nitrosamines formed when nitrite reacts with the amines naturally present in meat, particularly under high-heat cooking such as frying bacon.

Where you'll see E250 on a UK label

E250 is almost exclusively a cured-meat preservative. On a UK pack you will see it (or its potassium analogue E249, or its precursor E251 sodium nitrate) in:

• Bacon — back, streaky, smoked or unsmoked; nearly all cured
• Ham — cooked ham, parma, prosciutto, serrano, gammon
• Salami, chorizo, pepperoni — fermented and dry-cured sausages
• Hot dogs and frankfurters
• Corned beef and pastrami
• Bresaola, biltong and other air-dried beef
• Some sausages and burgers (cured-style varieties)
• Sliced deli meats — turkey, chicken, beef — where colour and shelf life are at stake
• Some pâtés, especially pork and liver

What the science shows

IARC Group 1 — "causes cancer"

In October 2015, after reviewing more than 800 studies, the IARC Monographs Working Group concluded there is sufficient evidence in humans that processed meat consumption causes colorectal cancer, and classified processed meat as Group 1: carcinogenic to humans. The published quantitative estimate is a 17% increase in colorectal cancer risk per 50g of processed meat consumed daily. Cancer Research UK attributes roughly 5,400 UK bowel cancer cases each year to processed-meat consumption. The classification is specifically the carcinogenic effect of processed-meat consumption — meat preserved by salting, curing, fermentation, smoking or other processes — not of fresh meat.

Nitrosamine chemistry — the mechanism

The mechanism is well-characterised. Nitrite reacts with the secondary amines abundant in meat protein, particularly under acidic or high-heat conditions, to form N-nitrosamines. Two of those — N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) — are themselves IARC Group 2A ("probably carcinogenic to humans") and have caused IARC Group 1-level concern when they have appeared at trace levels as contaminants in pharmaceuticals. The two routes that matter for diet are:

• During cooking: frying and grilling bacon at high temperature drives nitrosamine formation. Microwaving, baking and boiling generate substantially less.
• In the stomach: the acidic gastric environment converts residual nitrite plus dietary amines into nitrosamines during digestion. This is why ascorbic acid (E300, vitamin C) is co-added to UK cured meats — it competes for the nitrosating species and suppresses the reaction. It is also the reason a meal of cured meat eaten with citrus or vegetables high in vitamin C generates fewer nitrosamines than the meat eaten alone.

Methaemoglobinaemia in infants

At high acute doses, nitrite oxidises haemoglobin to methaemoglobin, which cannot carry oxygen. Infants under six months are particularly susceptible because of immature methaemoglobin reductase activity. UK weaning guidance is not to give cured meats to babies under six months. The risk in the modern UK food supply is low because cured-meat nitrite levels are tightly regulated, but it is the reason E250 has its own infant-specific guidance.

Regulatory status

UK / EU: approved as a curing salt with an EFSA Acceptable Daily Intake of 0.07mg/kg body weight per day — one of the most restrictive ADIs on the food-additive list, deliberately so. The EU lowered the maximum permitted levels in cured meat products in 2024 (Regulation (EU) 2023/2108), tightening the residual nitrite ceiling and tying it more closely to the minimum amount needed for botulism control. UK food law is aligned with the lower ceiling. Mandatory labelling as "preservative: sodium nitrite" or "E250".

NHS guidance: the NHS caps adult processed-meat consumption at 70g/day, citing the IARC Group 1 evidence and bowel-cancer risk.

US: FDA approved for use in cured meats with maximum levels around 200 ppm; USDA requires the co-addition of ascorbic acid or erythorbate to suppress nitrosamine formation.

The botulism trade-off

Sodium nitrite was originally adopted in industrial curing because it suppresses Clostridium botulinum spore germination in anaerobic cured meat. That public-health benefit is real and is the reason nitrite has not been banned outright in cured meats. The current regulatory direction in the EU is to keep nitrite for botulism control while lowering the residual levels and requiring co-additives (ascorbate) to suppress nitrosamine formation, rather than to remove it. Fresh meat — unprocessed chicken, beef, pork — does not need nitrite at all, and the IARC Group 1 classification does not apply to it.

Reading a UK label

Look for "E250", "sodium nitrite", or "preservative: E250" in the ingredients list of bacon, ham, salami, chorizo, hot dogs, pâté and cured beef. Related entries on the same packs:

• E249 — potassium nitrite (interchangeable with E250 for curing)
• E251 — sodium nitrate (reduced to nitrite during curing)
• E252 — potassium nitrate (saltpetre)
• E300 — ascorbic acid, often co-added as a nitrosamine suppressor

Products labelled "uncured" or "no added nitrites" on a UK pack will typically list celery juice concentrate, celery powder or a natural nitrate source — these convert to nitrite during curing and the IARC chemistry is unchanged. Genuine nitrite-free cured meat is grey-brown rather than pink. The NHS 70g/day cap applies to all of these — it is set on processed-meat intake, not on nitrite source.

Last updated: 11 May 2026