For many Australians, processed meats are a staple part of the diet. They’re integral to summer, as ubiquitous as a zinced-up nose or a backyard cricket game. Walk into most gatherings and these foods are being served. It’s the bacon sizzling on the barbecue, the cured ham at Christmas lunch and the salami on the grazing platter.
At the same time, many of us have now heard about a link between processed meats and colorectal cancer, which kills more than 5,000 Australians each year. So is this just a myth, or are we putting ourselves at increased cancer risk by including processed meats in our diet?
According to experts at UNSW Sydney, the answer is yes, these foods do contribute to cancer risk.
Australians eat a lot of meat, and significant proportion of that is processed. Data from the Organisation for Economic Cooperation and Development says we consumed approximately 110 kilograms per person per year in 2018, second only to the United States.
Based on the last national diet survey in 2011-12, up to a quarter of the meat consumed has been salted, cured, fermented, smoked or otherwise processed.
In 2015, the International Agency for Research on Cancer at the World Health Organization assessed over 800 studies to understand the link between processed meats and cancer. The studies excluded other cancer-causing factors like obesity, so that the effect of processed meats could be isolated.
The IARC’s Working Group was chaired by Professor Bernard Stewart from UNSW Medicine & Health, who is an internationally recognised expert in environmental carcinogenesis (cancer causation).
Ultimately the IARC classified processed meat as a carcinogen, meaning that they found sufficient evidence that eating processed meats causes colorectal cancer.
There are several explanations, the first being nitrites found in processed meat products.
‘Processed meat, at least historically, has been processed using sodium nitrite,’ said Professor Stewart. ‘That nitrite can react with molecules in the body to form N-nitroso compounds, which are cancer-causing substances.’
He says cooking processed meat, particularly over high heat or an open flame, can worsen the problem.
‘There are also carcinogens that are not inherently present in the meat but are generated during cooking. For example, polycyclic aromatic hydrocarbons and heterocyclic amines,’ said Professor Stewart.
Should processed meat carry a warning label?
If processed meat is a carcinogen, should packets of sausages and bacon carry warning labels, like cigarettes? According to Professor Stewart, it’s not that simple.
‘On the one hand, the evidence concerning cancer causation by consumption of processed meats is as definitive as the evidence that tobacco smoke and asbestos cause lung cancer. On the other hand, the same level of preventative action is in no way warranted,’ he argues.
Different carcinogens have different levels of impact on cancer risk. For tobacco smoke, the impact is high: the lifetime risk of lung cancer in a non-smoker is 1 per cent and in a heavy smoker it is 25 per cent. However, for someone who consumes processed meat frequently rather than moderately, their lifetime risk of colorectal cancer increases from 5 to 6 per cent.
This means that while there is strong evidence that eating processed meats causes colorectal cancer, the actual impact on cancer risk is relatively small.
Reducing the risk
Although eating salami may not be as dangerous as smoking cigarettes or breathing in asbestos particles, it does contribute to cancer.
But there may be ways to counteract the effects of processed meats in your gut – at least partially. This includes eating foods like fruits, vegetables and whole grains.
Associate Professor Sara Grafenauer from UNSW Medicine & Health, who is an Accredited Practising Dietitian, is researching how eating whole grains may protect against colorectal cancer.
Whole grains can have an indirect effect by combating obesity, but also directly prevent carcinogenic activity inside the gut. Importantly, dietary patterns with whole grains could mean prevention of disease, saving millions in healthcare costs.
‘The whole grain is a bundle of nutrients that has anti-carcinogenic properties, said Associate Professor Grafenauer. ‘It contains many compounds that are stimulating anti-oxidant activity in the gut and are being protective. Also, because whole grains are fibrous, they can also bind carcinogens and remove them from the gut.’
Of course another option is leave meat in all its forms off the menu entirely, and enjoy the health benefits of a balanced plant-based diet.