Processed meats like bacon, sausages and hot dogs can cause colon cancer and red meat is also a likely cause of the disease, World Health Organisation experts say, in a potentially heavy blow for the global meat industry.
The analysis of 800 studies from around the world by the International Agency for Research on Cancer (IARC) found “sufficient evidence in humans that the consumption of processed meat causes colorectal cancer”.
“Each 50-gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18 per cent,” it said in a statement.
The category includes meat that has been salted, cured, fermented or smoked — hot dogs, sausages, corned beef, dried meat like beef jerky or South African biltong, canned meat or meat-based sauces.
The finding supports “recommendations to limit intake of meat” — particularly in processed forms, the IARC said.
“In view of the large number of people who consume processed meat, the global impact on cancer incidence is of public health importance,” IARC official Kurt Straif said in a statement.
For an individual, the risk of getting cancer from eating processed meat was statistically “small”, the agency said, but “increases with the amount of meat consumed”.
The IARC added processed meat to the same group 1 category of cancer-causing agents as tobacco smoke and asbestos.
For unprocessed red meat — beef, veal, pork, lamb, mutton, horse or goat — the review found “strong” evidence of a cancer-causing effect, but not sufficient to place it in the same group of cancer-causing agents.
Instead, unprocessed red meat was classified as a “probable” carcinogen in its group 2A list that also contains glyphosate, the active ingredient in many weedkillers.
As for processed meat, the red meat risk was mainly for cancer of the colon and rectum, but also the pancreas and prostate, the report said.
The agency cited research attributing about 34,000 cancer deaths per year worldwide to diets high in processed meat.
As for red meat — if the suspected link were to be confirmed — it would account for some 50,000 cancer deaths per year worldwide.
The numbers were dwarfed by the estimated one million cancer deaths per year due to tobacco smoking, 600,000 from alcohol use, and more than 200,000 due to air pollution, the agency said.
Given that red meat is an important source of human nutrition, the results should help governments and regulatory agencies balance the risk and benefits of eating meat, the agency said.
It did not make a finding on whether the cooking method of meat affects the cancer risk.
The preparation of the IARC’s report has already prompted vigorous reactions from meat industry groups, which argue meat forms part of a balanced diet and that cancer risk assessments need to be set in a broader context of environmental and lifestyle factors.
In his first press conference, Australia’s new chief scientist Dr Alan Finkel said moderation was key when eating processed meat.
“Of hundreds and hundreds of environmental chemicals and food stuffs that were looked at, only one was not regarded as carcinogenic,” he said.
“So moderation is probably the best approach.”
Dr Christina Pollard of Curtin University’s School of Public Health in Western Australia said the findings were consistent with current Australian Dietary Recommendations.
“We’ve known for quite a long time that we need to limit high processed food consumption and to only have a moderate amount of lean meat,” Dr Pollard said.
“It’s really important to have a look at it in the context of the Australian population — what they currently eat and how that translates to diet.
“On average Australians, particularly men, eat about 20 per cent more meat than they need on any given day.”
Dr Pollard said Australians need to predominantly eat a diet that is high in fruits and vegetables and wholegrain cereals — with only a moderate amount of lean red meat.
The analysis was also consistent with research commissioned by the Cancer Council Australia and released earlier this month, Nutrition and Physical Activity Committee chair Kathy Chapman said.
“The study found that 2,600 bowel cancer cases each year could be attributed to excess red and processed meat consumption,” Ms Chapman said.
“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.
“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.”
Nutritionist Dr Rosemary Stanton said people should not eliminate all red meat from their diets.
“It’s fine to eat those things, like maybe a piece of bacon once a week, but not a great mound of ham and sausages every day,” Dr Stanton said.
“I think it’s a question of quantity that people really need to look at. It doesn’t mean none, it just means less.”
The report identified processed meats as any meat that had been transformed through salting, curing, fermentation, smoking or other processes to enhance flavour or improve preservation.
Dr Pollard said processed meats being placed in group one means there is convincing evidence that it does cause cancer in humans, but warned people not to get carried away.
“It doesn’t mean that eating meat is the same as smoking cigarettes,” she said.
“That interpretation would be wrong.”