New UK research has found that despite current concerns that eating processed meat is linked to a higher risk of cancer, it may just be processed meat treated with nitrites that poses a risk.
Carried out by researchers from Queen's University Belfast, the new analysis included 61 existing studies which looked at the relationship between consuming processed meat and the risk of developing bowel, colon, and rectal cancers.
The findings, published in the journal Nutrients, showed that despite concerns, not all processed meats appear to have the same level of cancer risk, and around only half the studies provided evidence for a link between processed meat and colorectal cancer (CRC).
In addition, when the researchers looked at processed meats which had been treated with sodium nitrite, a preservative which is used to enhance color and prevent food spoiling, they found that this figure jumped from half to 65% of the studies showing evidence of a link with CRC.
"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," explained Research Fellow Dr. William Crowe. "Almost two-thirds of studies found a link with cancer."
The WHO classified all processed meat as a carcinogen in 2015, including bacon, sausages, ham, and cured meats, such as prosciutto and salami. However, the researchers point out that some processed meat is nitrite-free.
For example, British and Irish sausages are not treated with nitrites, whereas other European and US sausages like frankfurters, pepperoni, and chorizo are. Moreover, some new types of bacon and ham are now available which are also nitrite-free.
The researchers believe that a distinction should now be made to show the different risks posed by nitrite-treated and nitrite-free processed meat.
"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 rigor and clarity and points the way for further research in this area," commented study lead author Dr. Brian Green.
As to whether we should cut processed meat containing nitrites out of our diets, Dr. Green says to keep following current guidelines.
"The current [UK] 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.
"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 that a strong link exists between nitrite-containing processed meat, such as frankfurters, and CRC," Green said.