Why does red and processed meat cause cancer (q)
There’s now a large body of evidence that bowel cancer is more common among people who eat the most red and processed meat. (There’s also growing evidence for a possible link to both stomach and pancreatic cancers, but this seems to be less clear cut than the link to bowel cancer.)
In red meat, the problems seem to start when a chemical called haem – part of the red pigment in the blood, haemoglobin – is broken down in our gut to from a family of chemicals called N-nitroso compounds. These have been found to damage the cells that line the bowel, so other cells in the bowel lining have to replicate more in order to heal. And it’s this ‘extra’ replication that can increase the chance of errors developing in the cells’ DNA – the first step on the road to cancer.
On top of this, processed red meats contain chemicals that generate N-nitroso compounds in the gut, such as nitrite preservatives.
Cooking meat at high temperatures, such as grilling or barbequing, can also creates chemicals in the meat that may increase the risk of cancer. These chemicals are generally produced in higher levels in red and processed meat compared to other meats.
But there are other theories too – some research has suggested that the iron in red meat could play a role, while others suggest the bacteria in the gut might play a supporting role too.
So despite what you may hear, it isn’t about the quality of the meat, or whether it’s from the local butcher or your supermarket. The evidence so far suggests that it’s probably the processing of the meat, or chemicals naturally present within it, that increases cancer risk.