CERTAIN meats - like some bacon and pepperoni - really can cause cancer, the "strongest evidence yet" suggests.
But, when it comes to processed meat, a one-size-fits-all blame game doesn't work, scientists said.
Bowel cancer link
They pointed the finger at bacon, sausages and ham, as well as prosciutto and salami.
But, a new study by experts at Queen's University in Belfast, has questioned that blanket generalisation.
They say they have found evidence to suggest not all processed meat is a risk - with the presence of nitrites being key.
Meats processed with nitrites do pose a risk - while those that are not, don't, according to the team.
Dr Brian Green, Dr William Crowe and Prof Chris Elliott from the uni's Institute for Global Food Security, reviewed all the recent studies looking at the link.
They said the results were inconclusive with around half of the studies suggesting a link with bowel cancer.
Our findings clearly show that not all processed meats, for example, carry the same level of riskDr Brian Green, Institute for Global Food Security
However, when the scientists only looked at studies that tested processed meat containing sodium nitrite - a preservative used to extend shelf life and enhance colour - they found evidence of a link between bowel cancer jumped from half to just under two-thirds or 65 per cent.
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."
Not all red meat a risk
Not all processed meat contains nitrates.
For example, British and Irish sausages are not processed with nitrites unlike many European and US sausages - like frankfurters, pepperoni and chorizo.
Some retailers in the UK are already selling new types of bacon and ham that have been processed without nitrites.
However, last year Prof Elliot called on the Government to tackle the issue, after it was found "nearly all" bacon and ham contains the cancer-causing chemicals.
The IGFS researchers now believe there is a need to define the health risk of both types of processed meat separately.
Co-author Prof 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."
More research needed
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 colorectal cancer 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."
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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 colorectal cancer," Dr Green concluded.
Bowel cancer is the second most deadly form of the disease in the UK, killing around 16,000 people every year.
A rise in young people being diagnosed has been blamed on diet and lifestyle.
A study published in April this year found a pack of bacon a week increases the risk of the bowel cancer by a fifth.
Yet, in September experts moved to reassure people. A team of Canadian scientists said the benefits of cutting down on bacon is unlikely to be worth it - branding it safe to eat.
The new findings are published in the journal Nutrients.