Processed meats containing this preservative are linked to colon cancer

Salami, parma ham and chorizo have long carried a cancer risk. [Photo: Getty]

Processed meats preserved with sodium nitrite may cause cancer, research suggests.

The World Cancer Research Fund recommends eating “very little, if any, processed meat because there is strong evidence it is a cause of bowel cancer”.

Whether hot dogs, bacon or sausages, processed meat is defined as an animal product that has been salted, cured, fermented or smoked to enhance its flavour and prolong its shelf life.

While all processed meats were once tarred with the “cancer brush”, scientists from Queen’s University Belfast argue only those preserved with sodium nitrite carry a risk.

READ MORE: Jeremy Bowen reveals bowel cancer diagnosis

A range of chemicals either found in meat, added during processing or produced when cooking, give processed meats a bad reputation.

Sodium nitrite can be converted into cancer-causing chemicals called N-nitroso compounds in the body, according to Cancer Research UK.

The preservative is added to meat to “prevent the growth of Clostridium botulinum and other food-spoiling bacteria”, the Belfast scientists wrote in the journal Nutrients.

Other controversial preservatives include haem, a pigment in red meat that damages cells and causes bacteria to release harmful substances.

Heterocyclic amines (HCAs) and polycyclic amines (PCAs) may also be to blame. These are produced when meat is cooked at a high temperature and can damage cells in the bowel.

READ MORE: What is bowel cancer?

To learn more about the dangers of processed meat, the Belfast scientists looked at 61 studies investigating the link between the popular foods and cancer.

Results came back muddled, with around half showing processed meat may trigger malignant tumours.

When the scientists only looked at sodium nitrite, however, this rose to just under two-thirds (65%).

“When we looked at nitrite-containing processed meat in isolation – which is the first time this has been done in a comprehensive study – the results were much clearer,” study author Dr William Crowe said.

“Almost two-thirds of studies found a link with cancer.”

Reports supposedly show “the removal of nitrite from processed meat does not compromise its safety”.

British and Irish sausages are not traditionally preserved with nitrites, unlike their European counterparts - chorizo, pepperoni and frankfurters.

Bacon and ham are also increasingly available without the controversial preservative, the scientists claim.

READ MORE: 'No proof' red and processed meat causes cancer

Based on their results, the team want to see the cancer risk of different forms of processed meats defined differently, according to whether they contain nitrites.

“Our findings clearly show not all processed meats carry the same level of risk,” lead author Dr Brian Green said.

“There is more research to be done before we can definitively prove causality regarding processed meat and cancer; there are so many variables when it comes to people’s diets.

“But based on our study, which we believe provides the most thorough review of the evidence on nitrites to date, what we can confidently say is a strong link exists between nitrite-containing processed meat, such as frankfurters, and colorectal cancer.”