In 2015, the World Health Organisation (WHO) published new findings that red meat and processed meat were carcinogenic.
Common red meat include beef, pork and lamb. Other meats that are considered ‘red’ include veal, mutton, horse and goat. This also includes fresh, minced or frozen meats.
Processed meat is meat that has undergone salting, curing, fermentation, smoking or other preservation or flavour-enhancing techniques. Common processed meats include bacon, ham, salami, sausages and hot-dogs. Others include corned beef, jerky, canned beef, meat by-products (blood) and even meat-based preparations and sauces.
WHO has classified processed meat as Group 1, which means ‘carcinogenic to humans’. They are able to classify this as they have convincing evidence to say that processed meats causes cancer.
WHO has classified red meat as Group 2A, which means ‘probably carcinogenic to humans’. Although there is a strong positive correlation between red meat consumption and developing colorectal cancer, there are chance, bias or confounding factors that may have played a role. Thus, they could not classify it in Group 1.
Red meat has an established link to colon, prostate and pancreatic cancer while processed meats has only been linked to colon cancer.
But how exactly does red meat and processed meats cause cancer? I believe understanding the mechanism behind these things will help make you a better informant for your body.
So first of all, what is cancer?
Cancer is caused by cells that have been damaged. These damaged cells try to repair themselves and if they can’t, they then undergo self-destruction. This is a process that protects our body from cancer and diseases. It prevents the cell from reproducing new cells that have the same damage.
Sometimes the damage occurs in this process and the process fails to protects us. The cell eventually becomes unregulated. This means that the cell doesn’t do what it normally does, but instead, it starts to produce lots and lots of new cells. Unfortunately, these new cells are also damaged and can become ‘cancerous’.
So what causes all this in the first place? How does the cell become damaged? How does this relate to red meat and processed meat?
Researchers have found chemicals present in red and processed meats that can cause cell damage and increase the risk of cancer. These chemicals are also added during the processing of meat or produced when cooking. A study has shown that red-meat-induced genetic damage to colon cells happens in just a few weeks!
The identified chemicals include:
- Nitrates and nitrites
- Heterocyclic amines (HCAs) and polycyclic amines (PCAs)
Red meat has a naturally red pigment called haem. Haem increases the risk of cancer in two ways. It can cause direct cell damage and can cause bacteria in the body to produce harmful chemicals.
Nitrates and Nitrites
Processed meats are kept fresh by adding nitrates and nitrites. When we consume these nitrates and nitrites, these compounds are converted to other chemicals known as nitrosamines and N-nitroso compounds (NOCs). Studies have shown these to be carcinogenic.
A study analysed the stool of people who ate a high-meat diet to those who ate vegetarian food. They found that the group who had a high-meat diet had high levels of NOCs while the vegetarian group had low levels of NOCs. Furthermore, the scientists were able to collect the cells that lined the colon. These cells are normally shed with every bowel movement. A large amount of cells from the high-meat diet group had NOC-induced DNA changes, while a lower proportion of cells were damaged in the vegetarian group.
Heterocyclic Amines (HCAs) and Polycyclic Amines (PCAs)
When meat is cooked at high temperatures or if the food is in direct contact with a flame or hot surface (such as grilling, barbecue or pan-frying), HCAs and PCAs are produced. These chemicals have been found to damage cells in the bowel and increase the risk of bowel cancer.
However, studies have also found high levels of HCAs to be produced in cooked chicken. So HCAs may play a role but are unlikely to be the only cause.
All of this means, that when you consume red meat and processed meat, your cells are exposed to these chemicals. These chemicals have the potential to damage the cells’ genetic material such as its DNA. Our cells are equipped with mechanisms to repair damaged DNA and the majority of the time, the repairs are successful. However, if any of these processes fail or the damage is in the genetic material that controls this self-repair function, cells can undergo malignant transformation.
So this means that with every consumption of red meat or processed meat, you are increasing your exposure and the number of potential cell damage. This will increase the number of times your cells will have to undergo self-repair and thus, increasing the chances of the process failing.