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This entry is part 2 of 5 in the series Google Hangouts

In our latest Google Hangout on Air, in partnership with Science on Google+, we focused on the recent headlines about processed meat and cancer risk. These were prompted by an expert meeting of the International Agency for Research on Cancer (part of the World Health Organisation), which concluded that processed meat is classified as a ‘definite’ cause of cancer while red meat is a ‘probable’ cause.

But what does this actually mean in practice? And what does it mean for the choices we make about the food we eat?

We were joined by two experts in this area – Dr Kathryn Bradbury from the University of Oxford and Professor Owen Sansom from our Beatson Institute in Glasgow – to explore the evidence that red and processed meat are linked to an increased risk of cancer. We also talked about the possible biological mechanisms behind a link, and discuss how people can reduce their risk of cancer.

As Kathryn explained, “I did see a lot of misleading headlines suggesting bacon is as bad as smoking, which isn’t really right.

“What the World Health Organisation does is that they put components or things like tobacco and processed meat into categories. And what they’ve said is that processed meat is in group 1, which is the same category as tobacco.

“That means that they concluded when they summarised the evidence that there is enough evidence to say that it [definitely] does cause cancer in humans. But with red meat there is a bit more uncertainty so it’s in group 2A, meaning that it probably does cause cancer.”

But comparing tobacco and processed meat the way the media did is rather misleading: although the evidence for the cancer-causing effects of processed meat and tobacco is equally strong, this doesn’t mean that the size of the effect is the same.

According to IARC, an extra 50 grams of bacon every day – roughly two rashers – increases bowel cancer risk by around 18 per cent.

But as Owen told us, “If you say ‘18 per cent’, that might sound quite a lot as an individual value – but… it’s still relatively small.”

Kathryn agrees. “We estimate that about 20 per cent of all cancers in the UK are caused by tobacco smoking, whereas about 3 per cent are caused by red and processed meat. If you look at it this way, if no one in the UK smoked we think we would prevent about 65,000 cases of cancer a year, whereas if no one ate red or processed meat we think we would prevent about just under 9,000 cases.”

That’s still a large number, so if people have particularly meaty diets, or are concerned about the amount of red or processed meat they’re eating, then the simplest thing to do is cut down and enjoy it in moderation. “It’s the boring balanced diet stuff,” Owen tells us.

We usually call it healthy eating, and you can find information about diet and cancer on our website. And we’ve written specifically about red and processed meat and cancer risk in this blog post.

Watch the Hangout in the video at the top of this post or on YouTube, and read a full transcript here. If you have any feedback about the Hangout or would like to suggest a topic for a future discussion, please leave us a comment below.

Kat