Not all processed meat has the same cancer risk, new research suggests.
A study published in the journal Nutrients has questioned the World Health Organisation’s blanket classification of processed meat as carcinogenic.
Researchers say they have identified gaps between processed meat treated with nitrates and those that are not.
Dr Brian Green, Dr William Crowe and Professor Chris Elliott, from the Institute for Global Food Security (IGFS) at Queen’s University, Belfast, reviewed all recent, English-language studies into consumption of processed meat and cancer risk.
They said the results were inconclusive with around half the studies indicating a link with colorectal cancer (CRC).
The researchers added this may explain the appearance of contradictory claims in recent years.
However, when studies which only tested the consumption of processed meat containing sodium nitrite – a preservative used to extend shelf life and enhance colour – were isolated, scientists found evidence the link to CRC jumped from half to just under two-thirds (65%).
Dr Crowe said: “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.”
In 2015 the WHO classified all processed meat as a carcinogen – including bacon, sausages and ham as well as continental European products like prosciutto and salami.
However, not all processed meat contains nitrates.
For example, British and Irish sausages are not processed with nitrites even though many of the European and US sausage equivalents are, such as frankfurters, pepperoni and chorizo.
Some retailers in the UK are already selling new types of bacon and ham that have been processed without nitrites.
The IGFS researchers now believe there is a need to define the health risk of both types of processed meat separately.
Co-author Professor Elliott, who carried out the UK Government’s inquiry into food safety after the horsemeat scandal, said the study brought more clarity to what has been a confusing area for the food industry and the public.
He explained: “Because there have been conflicting claims in the scientific community and the media about which types of meat may be carcinogenic, this study couldn’t have come at a better time.
“It brings much-needed rigour and clarity and points the way for further research in this area.”
Lead author Dr Green added: “It’s important we eat a healthy, balanced diet in line with the government’s ‘Eatwell Guide’.
“The current Department of Health guidance advises the public to consume no more than 70g of red or processed meat per day.
“That remains the guidance, but we hope that future research investigating the link between diet and CRC will consider each type of meat individually rather than grouping them together.
“Our findings clearly show that not all processed meats, for example, carry the same level of risk.”
The scientists say more research is needed before they can definitively prove causality regarding processed meat and cancer.
“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 that a strong link exists between nitrite-containing processed meat, such as frankfurters, and CRC,” Dr Green concluded.