Eating processed meats does cause bowel cancer, the World Health Organization has said in a report published today (26 October).

The WHO's International Agency for Research on Cancer (IARC) said there was "sufficient evidence" processed meat such as ham and corned beef causes colorectal cancer. The body classified the foods in its Group 1 list for items that are "carcinogenic to humans". 

The report, conducted by a group of 22 experts from ten countries, said the consumption of processed meat was associated with "small increases" in the risk of cancer. It said the risk "generally increased" with the amount of meat consumed and noted an analysis of data from ten studies estimated each 50g portion of processed meat eaten daily increases the risk of colorectal cancer by 18%.

The report classified red meat – such as beef, veal, pork and lamb – as "probably carcinogenic to humans". The assertion was "based on limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect", the IARC said.

According to the IARC, limited evidence means a positive association has been observed but other explanations for the observations, such as "technically termed chance, bias, or confounding" could not be ruled out.

"For an individual, the risk of developing colorectal cancer because of their consumption of processed meat remains small, but this risk increases with the amount of meat consumed," says Dr Kurt Straif, head of the IARC Monographs Programme. "In view of the large number of people who consume processed meat, the global impact on cancer incidence is of public health importance."

Dr Christopher Wild, director of the IARC, added: "These findings further support current public health recommendations to limit intake of meat. At the same time, red meat has nutritional value. Therefore, these results are important in enabling governments and international regulatory agencies to conduct risk assessments, in order to balance the risks and benefits of eating red meat and processed meat and to provide the best possible dietary recommendations."

In 2007, the World Cancer Research Fund advised consumers should avoid "processed meats such as bacon, ham, salami, corned beef and some sausages". The fund said eating red meat should be limited to 500g a week.

At the time, the report came under fire from the meat industry. The American Meat Institute criticised the "alarmist messages" in the report and said the findings should be treated with "scepticism".