Global health experts are to warn that bacon, ham and sausages are as big a cancer threat as cigarettes in an upcoming report.
The World Health Organisation (WHO) will publish a report on Monday on the dangers of eating processed meats.
It is expected to list processed meat as a cancer-causing substance, while fresh red meat is also expected to be regarded as bad for health.
The classifications, by the WHO’s International Agency for Research on Cancer, are believed to regard processed meat as “carcinogenic to humans”, the highest of five possible rankings, shared with alcohol, asbestos, arsenic and cigarettes.
The World Cancer Research Fund (WCRF) has warned for several years that there is “strong evidence” that consuming a lot of red meat can cause bowel cancer.
It also says there is “strong evidence” that processed meats - even in smaller quantities - increase cancer risk.
One possible reason is that the compound that gives red meat its colour, haem, may damage the lining of the bowel.
In addition, when meat is preserved by smoking, curing or salting, or by adding preservatives, cancer-causing substances (carcinogens) can be formed.
Studies also show that people who eat a lot of red meat tend to eat fewer plant-based foods that protect against cancer.
The WCRF advises that people can reduce their bowel cancer risk by eating no more than 500g (cooked weight) per week of red meat, such as beef, pork and lamb.
It also says people should eat processed meats such as ham, bacon and salami as little as possible.
Foods like hamburgers, minced beef, pork chops and roast lamb are also regarded as red meat.
As a rough guide, the WCRF says 500g of cooked red meat is the same as 700g of raw red meat.
Processed meat is meat which has been preserved by smoking, curing or salting, or by the addition of preservatives.
Examples include ham, bacon, pastrami and salami, as well as hot dogs and some sausages.
An expert from the Meat Advisory Panel, which is funded by the meat industry, said there was no need to avoid red meat.
Professor Robert Pickard, from the University of Cardiff and a member of the Meat Advisory Panel, said: “No one food gives you cancer and speculating ahead of the World Health Organisation announcement creates a situation of confusing messages.
“What we do know is that avoiding red meat in the diet is not a protective strategy against cancer.
“The top priorities for cancer prevention remain smoking cessation, maintenance of normal body weight and avoidance of high alcohol intakes.
“In fact, a large European study showed that bowel cancer rates were similar in vegetarians and meat-eaters, suggesting that meat avoidance does not help prevent bowel cancer. Choosing a meat-free diet is a lifestyle choice - it is not vital for health.”