The publication of research into the cancer risks associated with meat by the International Agency for Research in Cancer (IARC) has been met by some alarmist headlines. It's important to put what the agency has said in context.
Firstly, the World Health Organisation subsidiary has distinguished between the cancer-causing potential of red meat and that of processed meat.
It measures carcinogenicity (the potential for a substance to cause cancer) on a four-point scale from one, meaning the substance is carcinogenic to humans, to four, a classification which means it is probably not carcinogenic to humans.
IARC has labelled processed meat as a category 1 carcinogen. Processed meats include ham, burgers, sausages and bacon. They have been modified to either extend shelf life or change the taste of the meat.
This raises the possibility that it is chemicals involved in the processing which could be increasing the cancer risk.
According to the agency when consumed daily, each 50g of processed meat increases the risk of colon cancer by 18 per cent.
Limited evidence
Red meat, on the other hand, has been designated category 2A, which means it is probably carcinogenic to humans but with limited scientific evidence to show a link between eating it and developing cancer.
IARC said that if the association between red meat and colon cancer were proven, then the risk of developing bowel cancer could increase by 17 per cent for every 100g of red meat eaten daily. And it also pointed to a possible link between red meat consumption and cancer of the pancreas and prostate cancer.
Risks expressed as percentages can be somewhat opaque and it may be helpful to look at the absolute risk instead; one expert has linked red meat consumption to about three extra cases of bowel cancer per 100,000 adults in developed countries.
It’s worth emphasising the role of the IARC expert panel in making this designation.
Their task is to undertake a theoretical exercise in exact labelling, just as it has done with hundreds of other potential cancer causing agents such as the chemicals found in tobacco smoke, benzene and asbestos.
Practical risk
But is up to other expert groups to now interpret the practical risk to human health of consuming red meat and processed meat.
The Irish Cancer Society has responded with a recommendation to avoid processed meats and to reduce the consumption of cooked red meat to 500g per week.
These groups will have to consider issues such as the inclusion of processed meats in an apparently healthy Mediterranean diet, the nutritional value of red meat (it is a valuable source of iron and Vitamin B12) and the possible role of different cooking styles in promoting the carcinogenicity of meat.
While the inclusion of processed meat in the top cancer risk category places it alongside smoking, it would be premature to see eating bacon and sausage as being of equal risk to consuming tobacco. Cancer development is a complex mix of genetic predisposition, environmental triggers and immune system factors.
The best prescription for avoiding cancer remains regular exercise, weight control, a diet full of fruit, vegetables and fibre, not smoking and limiting one’s alcohol intake.