The World Health Organisation (WHO) has today warned that processed meats such as bacon and sausages are as big a cancer threat as cigarettes.
The health authority has placed cured and processed meats in the same category as carcinogenic substances such as asbestos, alcohol, arsenic and tobacco.
Red meat is also "probably" carcinogenic, with associations mainly with bowel cancer, but also with pancreatic cancer and prostate cancer, according to the report
The report found eating 50g of processed meat a day (one sausage or two rashers of bacon) increases the chance of developing bowel cancer by nearly 20%.
The International Agency for Research on Cancer (IARC), the cancer agency of the WHO, said: "Processed meat was classified as carcinogenic to humans, based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer."
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 and also linked processed meats - even in smaller quantities - to an increased cancer risk.
Researchers believe one possible reason for the cancer link 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.
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Dr Kurt Straif, head of the IARC Monographs Programme, said: "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.
"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 IARC, said: "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."
The IARC 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 most influential evidence came from large prospective cohort studies conducted over the past 20 years.
The consumption of meat varies greatly between countries, from a few per cent to up to 100% of people eating red meat, and somewhat lower proportions eating processed meat, the report said.
According to the Meat Advisory Panel, in the UK more than nine out of ten people eat meat.
An expert from the panel, which is funded by the meat industry, said there was no need to avoid red meat and linking it to smoking is "ridiculous".
Professor Robert Pickard, from the University of Cardiff and a member of the Meat Advisory Panel, said: "Red and processed meat do not give you cancer and actually the IARC report is not saying that eating processed meat is as harmful as smoking. In fact comparing red meat to smoking is ridiculous.
"Looking at the report itself I am very surprised by IARC’s strong conclusion on categorising processed red meat as definitely and red meat as being probably carcinogenic to humans given the lack of consensus within the scientific community and the very weak evidence regarding the causal relationship between red meat and cancer.
"There are many substances classed as carcinogenic such as air pollution, contraceptive pills and working as a painter. Interestingly IARC has even noted coffee, working as a hair dresser and shift working in the same category as red meat."
He added: "The IARC ruling states that eating 50g of processed red meat every day leads to a very small increase in the risk of bowel cancer. In the UK we are only eating 17g on average of processed meat a day. So we would have to eat three times the amount of processed meat to increase the risk."
But Claire Bass, executive director of Humane Society International/UK, said that it's time health ministers paid attention to the information provided and took action.
"When the world's leading health authority declares that bacon and ham are carcinogenic, it's time for consumers and government health ministers to listen," she says.
"This latest research needs to underpin a turning point in global diets – we simply can’t afford to continue damaging our health, the environment and causing immeasurable animal suffering, with such high levels of meat consumption, not to mention other animal products.
"As well as helping to prevent some cancers and heart disease, plant-based diets are also being used to reverse chronic conditions such as type-2 diabetes and obesity, all of which are of course costing the NHS millions."
She added: "The WHO's findings give further compelling weight to the very serious public health implications of processed meat consumption.
"A recent YouGov poll commissioned by HSI UK revealed that more than a quarter of people already believe that the most important reason to eat plant-based food is that it’s good for our health, and today’s report can only help that figure to rise.
"It's time now for the government to step up to the plate and amend the ‘Eatwell’ dietary guidelines to take this into account.
"There’s a clear need for a government-led campaign to educate consumers, and our own EatKind campaign will also help support this much-needed dietary shift with public education, and pushing for greater availability of healthy plant-based options in our shops, dinner halls, canteens and restaurants."