Medical Matters: Do I give a rashers about risk of cancer? Show me the evidence

Just two rashers of bacon a day raises your risk of cancer – health chiefs put processed meat at same level as cigarettes”

Were you as taken aback as I was to read headlines like this one on the October bank holiday? Indeed, for anyone who had enjoyed a grilled breakfast that morning, it may have triggered a momentary bout of indigestion. Processed meat as harmful as cigarettes: how could that be?

The answer, of course, is that the risk of cancer from eating rashers and sausages is nowhere near that of consuming tobacco. However, due to poor communication by the WHO’s International Agency for Research on Cancer (IARC) and less than incisive media coverage, some really garbled public health messages ensued.

The key to understanding the international agency's announcement lies in its remit, which is to examine the evidence about whether processed meat and red meat causes cancer. Its report is not about risk, something the agency failed to communicate adequately in its announcement.

The agency measures carcinogenicity – the potential for a substance to cause cancer – on a four- point scale from 1, meaning the substance is carcinogenic to humans, to 4, a classification that means it is probably not carcinogenic to humans. It labelled processed meat as a category 1 carcinogen.

Processed meats include ham, burgers, sausages and bacon. They have been modified either to extend shelf life or to change the taste of the meat. Red meat, on the other hand, was 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.

First mistake

Mistake number one, in my opinion, was to make an announcement about processed meat and red meat on the same day, especially as each had been assessed as having a different potential to cause cancer.

This made a confused health message almost inevitable.

The agency’s press release didn’t help. It does not have a role in providing guidelines on health risk, yet the press release goes on to discuss a 2011 meta-analysis review, which found a 17 per cent increased risk of bowel cancer from eating 100g of red meat a day and an 18 per cent increase from consuming 50g of processed meat a day.

While I can understand how the agency may wish to be identified as a separate agency within the World Health Organisation, running solo with an announcement of this import without public health expert input was not a good idea.

This should have been a WHO headline event with input from the agency, but with the main message made simple and driven by senior public health communicators. Once the cancer research agency strayed into discussing health risks, risk inevitably became a major part of media coverage.

We know the risk of developing cancer doubles for every 10 years that someone smokes; to make personal choices, consumers need to hear how long they must eat a defined amount of processed meat to produce a stated numerical risk.

If you are really going to address the public health risks of processed meat, you need to simultaneously discuss its possible effect on diseases other than cancer.

Some reference to the nutritional benefits of meat would also help a balanced debate.

Cancer Research UK has some helpful statistics that help to put the "processed meat at same level of cigarettes" headlines to bed.

Some 21 per cent of bowel cancers are caused by processed or red meat, while 86 per cent of lung cancers are triggered by tobacco, 19 per cent of all cancers are caused by tobacco while just 3 per cent of all cancers are linked with meat consumption.

If any reader finds out how many rashers of bacon a day for how many years causes a “Y” per cent increased risk of bowel cancer, please let me know. Then I’ll look at changing my diet.

mhouston@irishtimes.com; muirishouston.com Second Opinion: Jacky Jones, page 16