A working group of 22 experts from 10 countries, led by Professor Bernard Stewart from the Cancer Council Australia, classified processed meat as "carcinogenic to humans" based on "sufficient evidence" in humans that eating processed meat causes colorectal cancer.
The group also classified the consumption of red meat
as "probably carcinogenic to humans". This association was observed mainly for colorectal cancer, but associations were also seen for pancreatic cancer and prostate cancer.
Meat consumption and its effects
The IARC Working Group considered more than 800 studies that investigated associations of more than a dozen types of cancer with the consumption of red meat or processed meat in many countries and populations with diverse diets.
The experts concluded that each 50g portion of processed meat eaten daily increases the risk of colorectal cancer by 18%.
"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."
Should I cut these meats out of my diet?
But experts say the news isn't cause for you to throw tonight's steak in the bin or take ham off the Christmas menu.
"No-one's proposing that we ban bacon, put warnings on hot dogs or take beef off the barbie. But this WHO review provides compelling evidence that the long-term consumption of red meat and/or processed meat increases your risk of cancer," says Dr Bernard Stewart, conjoint professor with the School of Women's & Children's Health at the University of New South Wales and chief scientific advisor for the Cancer Council Australia.
"The findings provide a new degree of certainty for health authorities who produce evidence-based dietary guidelines," Stewart says.
"The National Health and Medical Research Council's current dietary guidelines recommend consuming no more than 65 to 100 grams of cooked red meat, three to four times a week," Kathy Chapman of Cancer Council Australia says.
"Cancer Council recommends staying within this guideline but we don't encourage avoiding red meat altogether – lean red meat is a good source of iron, zinc, vitamin B12 and protein."
"Processed meats, however, are nutrient poor by comparison and more likely to be high in fat, salt and nitrates. This is why we recommend reducing or limiting processed meat intake," she adds.
Dr Rosemary Stanton, nutritionist and member of the NHMRC's Dietary Guidelines Working Committee, agrees. "No one doubts that red meat is a nutritious food," she says. "Nor is there any nutritional reason to remove it from the diet."
But she adds: "The extensive analysis from WHO's expert group confirms the message of the Australian guidelines – to limit consumption of red meat."
"The guidelines also moved processed meats out of the basic food groups to the list of 'discretionary' foods. These foods are not essential in a healthy diet and should either be omitted or consumed only occasionally or in small quantities," she says.
It seems timely that we should have a reminder of these recommendations. Australia had the fifth highest rate of beef and veal consumption and the highest sheep meat consumption (kg per capita) of all OECD countries in 2014. And a recent survey found that Australian men ate 700g of red meat on average each week, and women 520g – both well above what's recommended in the guidelines.
Are cancer risks from smoking and processed meats comparable?
While processed meat has been classified by the IARC in the same category as tobacco, it doesn't mean they're equally dangerous. "The IARC classifications describe the strength of the scientific evidence about an agent being a cause of cancer, rather than assessing the level of risk," explains the WHO.
Chapman stresses the importance of putting the cancer risks associated with red and processed meat into context in terms of other preventable cancer causes.
"While Cancer Council's recent research found that red and processed meat accounted for around 2600 cancer cases each year, 11,500 cancer cases each year are caused by tobacco, 3,900 cancer cases are attributable to obesity and overweight and 3,200 are attributable to alcohol. An overall healthy lifestyle, including diet, is important to reduce your cancer risk," Chapman says.
Exactly what meats are we talking about?
The IARC provides the following definitions:
Processed meat refers to meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation. Most processed meats contain pork or beef, but processed meats may also contain other red meats, poultry, offal, or meat byproducts such as blood. Examples of processed meat include hot dogs (frankfurters), ham, sausages, corned beef, and biltong or beef jerky, as well as canned meat and meat-based preparations and sauces.
Red meat refers to all types of mammalian muscle meat, such as beef, veal, pork, lamb, mutton, horse, and goat.