How, and why, is red meat linked to bowel cancer?
When talking about the environmental, or habitual, culprits of cancer, we often mention the usual suspects: smoking, sun-burn, air pollution… However, one other major culprit roams relatively unremarked upon: red and processed meat.
Red meat is red in colour when raw: so beef, pork and lamb all count. Processed meat refers to meat that has been preserved in some way, ie by smoking, curing or adding preservatives. Examples here include ham, sausages and salami.
So far so delicious, and relatively nutritious… Meat is a great source of protein, B vitamins and minerals such as iron, zinc and selenium. It is also one of the main natural sources of vitamin B12. But with these benefits come some quite significant negatives. In fact, both red and processed meats are listed by the World Health Organisation (WHO) as carcinogens, meaning they there is evidence that they cause cancer. But how do they cause cancer? And why, in particular, bowel cancer?
The culprits are n-nitroso compounds, formed when haem (the molecule that gives red meat it’s colour) and nitrates (used to preserve processed meats) break down in the bowel. Interestingly, these are produced in higher numbers if the meat has been cooked at high temperatures (ie frying, grilling, bbq-ing). N-nitroso compounds might not sound particularly sinister, but these little fellas are attracted to DNA in the bowel wall lining where they bond to one of the main nucleobases: guanine. Your body recognises that guanine has something latched onto it that shouldn’t be and tries to remove it, often tearing the DNA apart in the process.
Now cancer is formed by mutations in DNA: errors in the bases can lead to jumbled growth instructions, meaning that cells grow out-of-control and form tumours. Therefore, the act of cleaving n-nitroso molecules from DNA — and breaking parts of it whilst doing so — increases the chance of mutations that could ultimately lead to cancer. The fact that this process occurs in the bowel is why the WHO state that a diet higher in red and processed meats likely leads to an increased risk of bowel cancer.
But why, if DNA is being ripped apart, does the human body not step in with its own repair mechanisms? Well it does — but the more times it has to step in, the more chances it has of making a mistake. A human body’s repair response system is incredible but the more it is used, the more it can go wrong.
So what can humans do to minimise this risk? There are a few changes to your lifestyle that can potentially cut down your risk of developing it in the future:
In the meantime, get familiar with your faeces! If you notice a change in your bowel habits, in your poo itself, or notice any other symptoms of bowel cancer, go and talk to your GP.
If you’d like more information, or further support, please visit Bowel Cancer UK.