Processed meats such as ham, sausages and bacon have been placed alongside tobacco and alcohol as a major cancer hazard, according to findings released by an arm of the World Health Organisation (WHO).
The International Agency for Research on Cancer (IARC), citing analysis of more than 800 studies, announced on Monday (Oct 26) that it found enough evidence to rank processed meats as group 1 carcinogens, due to it causing colon cancer.
Colon cancer - also known as colorectal or bowel cancer - affects the large intestine, which consists of the colon and rectum.
"In view of the large number of people who consume processed meat, the global impact on cancer incidence is of public health importance," said the IARC's Dr Kurt Straif in a statement.
What are the implications of this revelation and how does it impact Singaporeans? Here are 7 things to know.
1. Colorectal cancer is the most common cancer in Singapore
Between 2010 and 2014, 9,324 people were diagnosed with the cancer. It was the most frequent cancer among men during the same period with 17.2 per cent of all cancers, while it was ranked second (13.3 per cent) behind breast cancer among women.
Colorectal cancer is also one of the top death-causing cancers - it ranks second (1,944 deaths from 2010-2014) behind lung cancer for men and third (1,782 deaths) behind breast and lung cancer for women.
2. The IARC's findings are not new
In an article titled "What is cancer" on the Health Promotion Board's (HPB) website, it states that the chemicals used to process food such as ham, bacon and luncheon meat may form cancer-causing substances when digested. The HPB also advises Singaporeans to "avoid salted, pickled, preserved and processed foods, if you can or have them less often".
Research by the World Cancer Research Fund, which was published in 2007 and ratified in 2011, showed strong evidence that consuming processed meat increased the risk of colorectal cancer. It had said then that if people ate less than 10g of processed meat a day, there would be 4,000 fewer cases of the cancer.
A 2013 study conducted on half a million people across Europe concluded that processed meats were linked to cardiovascular disease, cancer and early death.
In that same year, a report published by the National Registry of Diseases Office, which studied the trends of colorectal cancer in Singapore between 2007 and 2011, also said that increased processed meat consumption was one of several risk factors for the cancer.
3. There are about 120 agents in the WHO's list of group 1 carcinogens
Processed meat now finds itself in the company of tobacco, alcohol, radioactive substances like plutonium, and outdoor air pollution as the number one cause of cancer.
There are also two other categories, 2A (probably carcinogenic) and 2B (possibly carcinogenic), listed by the WHO which contain 75 and 300 agents respectively. Agents in 2A include red meat, steroids, and shift work that disrupts sleep patterns, while those in 2B range from chloroform and welding fumes to pickled vegetables.
4. Processed meat account for a comparatively small percentage of cancers
The risk associated with each carcinogenic agent, however, varies. Smoking accounts for more than 80 per cent of all lung cancers, while an estimated 20 per cent of colorectal cancers are caused by processed or red meat.
An estimated 34,000 deaths from cancer each year can be attributed to a diet high in processed meat, compared to a million cancer deaths from smoking and 600,000 from excessive drinking habits.
As Dr Straif put it: "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."
5. What exactly can be defined as processed meat?
This 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 by-products such as blood.
Examples include hot dogs, ham, sausages, corned beef, biltong (a type of cured meat popular in South Africa), beef jerky and canned meat.
Scientists believe that the processes result in the build-up of carcinogenic chemicals such as N-nitroso-compounds and polycyclic aromatic hydrocarbons in the meat.
6. Is there a prescribed limit to eating processed meat?
According to the IARC, each 50g portion of processed meat eaten daily increases the risk of colorectal cancer by 18 per cent.
But experts have said that the research should not stop people from consuming processed meat, as meat in general still remains a good source of nutrients such as zinc, protein and vitamin B12.
The key is to eat them in moderation.
"If you eat lots of it, you may want to think about cutting down. You could try having fish for your dinner rather than sausages, or choosing to have a bean salad for lunch over a BLT (bacon, lettuce and tomato sandwich)," said Tim Key, an epidemiologist at Cancer Research UK.
And as nutrition expert Gunter Kuhnle from the University of Reading pointed out: "Processed meat can be part of a healthy lifestyle - smoking can't."
7. How has this affected the global meat industry?
Predictably, the IARC's announcement has triggered an outcry among meat producers around the world. The North American Meat Institute (NAMI) claimed the IARC had "tortured the data to ensure a specific outcome".
It cited followers of the Mediterranean diet, who eat double the recommended amount of processed meats, in countries such as Spain and Italy as having some of the longest lifespans in the world.
An advisory board funded by meat producers in Britain also slammed the findings, saying that avoiding processed meat was not a protective strategy against cancer.
Australia, one of the world's top meat exporters, ridiculed the report as a "farce" for suggesting that sausages and ham were as lethal as cigarettes.
The country's Agriculture Minister Barnaby Joyce, speaking on radio, said: "If you got everything that the WHO said was carcinogenic and took it out of your daily requirements, well you are kind of heading back to a cave."
"If you're going to avoid everything that has any correlation with cancer whatsoever - don't walk outside, don't walk down the streets in Sydney, there's going to be very little in life that you do in the end."
Sources: BBC, AFP, Health Promotion Board, The Washington Post, National Registry of Diseases Offices, The Guardian