The research is sound, but can we eat these meat foods safely or not?

People were generally shocked and surprised that there might be so much danger hidden in a “full Irish” breakfast or a breakfast roll. Even more unexpected was the small amount of processed meat in the diet – less than two sausages or two rashers per day – needed to increase the risk of developing bowel cancer.

There has been much reassurance since from the Irish Farmers’ Association, the Food Safety Authority and the Department of Health that in fact eating these food items will not cause sudden death and that red meat also carries health benefits, such as being rich in iron. So why does the confusion exist? Can we eat these foods safely or not?

There is no doubt that the research carried out by the World Health Organisation’s International Agency for Research on Cancer is sound and can be trusted. The agency analysed existing information on the subject, mining data from 800 different studies on cancer in humans.

Of these, 700 included epidemiological data on the consumption of red meat and 400 on processed meats.

It was frightening to hear that the agency had decided to place processed meats in the same “Group 1: carcinogenic to humans” category among other known carcinogens such as tobacco and asbestos. It placed red meats in a slightly less dangerous “Group 2A: probably carcinogenic to humans” group, but it still seemed as though eating red meat must be dangerous.

The agency was very clear, however, to clarify that inclusion in Group 1 did not mean that eating sausages or salami or ham sandwiches was as much of a hazard as smoking a pack of cigarettes a day. Nor did it mean that we should give up all consumption of burgers or steak.

While it did warn that eating 50g of processed meats per day increased the risk of colorectal cancer by 18 per cent, this does not mean we face an 18 per cent increase in our chances of getting bowel cancer from a few sausage rolls a day.

On Friday the World Health Organisation said the original message from its cancer report had been "misinterpreted" and clarified it was not asking people stop eating processed meats.

Unfortunately, the confusion comes down to terminology and the use of the word “risk”. Most of us assume risk means the probability that cancer will occur. But the agency was not looking at this probability; it was measuring “hazard”.

An agent is considered a cancer hazard if it is capable of causing cancer under some circumstances. Smoking is a known and certain hazard, but many will smoke and not die of smoking- related diseases.

The agency, after ploughing through those 800 studies, decided that yes, there was convincing evidence that daily consumption of these meats also represented a hazard, but a smaller hazard than smoking.

It did not, however, tell us anything about the “relative risk”, the probability that cancer will occur. The agency’s research programme “evaluates cancer hazards but not the risks associated with exposure”, it says.

So the agency’s warning is that the more meat we eat, the greater the hazard we face. But the increased risk of cancer arising if we eat these foods is only 0.12 per cent, not 18 per cent, or around three cases per 100,000 people.