Processed meat and Cancer: What is the Risk?
Yesterday I hosted a Hangout with two scientists to talk about the links between diet and cancer, on the back of the "omg bacon gives you cancer"
stories that broke out a few weeks ago. As part of my job as a science communicator at CRUK, I get access to researchers who study this, so I was very pleased to chat with Dr Kathryn Bradbury
, a nutritional epidemiologist, and Professor Owen Sansom
, a molecular biologist. It was a good mix of research interests because we were able to approach this question from a population/clinical angle, but then also dive into the mechanism behind what we see, i.e. how exactly does red and processed meat increase cancer risk. You can watch the full video at https://www.youtube.com/watch?v=jS1QW74wJRw
. Joining me was my colleague Dr Kat Arney
, who co-hosts these cancer Hangouts with me.
First we discussed how we find out what things in the diet are linked to cancer - Kathryn explained how we design studies looking at hundreds of thousands of people from the general population. We ask them questions about their diet and lifestyle, and then we follow them up over many years to see who develops cancer. Then we look back and see what effect their diets had on their cancer development, for example did vegetarians get less cancer than those who ate lots of red and processed meat. Having large-scale population based studies like this is the only way we can gather evidence for the risk factors for cancer; lots of people mean better statistical analyses, which means the data is more rigorous, rather than the anecdotal "oh my neighbour drank a miracle kale juice cleanser every day and he never got cancer" theories.
Owen talked about the mechanisms for cancer development, particularly bowel cancer, and how it is linked to the molecules found in red and processed meat. The cells lining our gut get completely replaced every 3-4 days, so they are cells with a high rate of cell division. These cells are also exposed to cancer-causing chemicals (i.e. carcinogens) from the food we eat, depending on our diet. With red and processed meat, eating a lot of it means that the gut cells are also exposed to a lot of the carcinogens found in them. For example red and processed meats have a lot of nitroso products, and these can be carcinogenic. How exactly does that work? These chemicals cause mutations to the DNA in the cells lining the gut. Owen also talked about how it can cause more mutations in key tumour-suppressor genes (i.e. genes that normally suppress cancer, but when these genes are mutated it leads to cancer - I discussed one such pathway here https://goo.gl/6CSn10
). Haem iron from red meat is also a culprit because it has shown to cause DNA damage. Intriguingly, Owen also brought up how the bacterial population in our gut (i.e. our microbiome) can change depending on what we eat, which in turn can have an impact on whether the cells lining our gut can end up with mutations that can lead to cancer.
Finally we finished up by talking about cancer prevention. We know that 4 in 9 cancers are linked to preventable causes, so what are the things we can do to lower our cancer risk? The answers were unsurprising; give up smoking (if you smoke), reduce instances of sun-burn, eat a well-balanced diet with moderate amounts of red and processed meat (i.e. bacon with every meal every day is probably a bad idea), along with physical activity.
Of course this is much easier said than done, because people often want quick-fix miracle cures/pills/whatever that lets them keep living unhealthy lives without feeling bad for it. Unfortunately there are no such shortcuts that are scientifically valid. Listening to Kathryn and Owen discuss the cancer risk from red and processed meat, along with the mechanistic explanation of 'how'
was incredibly useful, and I hope you enjoy watching this Hangout :)