A meaty issue
A report by the International Agency for Research on Cancer (IARC), a group composed of 22 experts from 10 different countries, recently concluded that processed meat and most likely red meat are a cause of colorectal cancer. And this is indeed the second leading cause of cancer death in Australians.
What is meant by red meat?
Red meat is the muscle flesh that comes from cattle, sheep, pigs and goats. Pork looks white when it is cooked, but is typically red when raw because of its high haemoglobin content.
Fish and poultry are not part of the red meat family.
Processed meat however is any type of meat (including poultry) that has undergone salting, curing, fermentation, the addition of additives or smoking to enhance its flavour or to improve preservation.
Bacon, hot dogs, sausages, ham all belong here.
Establishing a link between red and processed meats and colorectal cancer is one thing, but what indeed is the mechanism?
There are several plausible culprits.
Firstly, the pigment that gives red meat its colour is haemoglobin. In the gastrointestinal tract, haemoglobin is broken down to a family of chemicals called H-nitroso compounds (NOCs).
These NOCs have been found to damage cells that line the bowel, causing them to divide and replicate to repair the damage. It is this increased cell replication that can be the first step on the road to bowel cancer. Processed meats have a double-whammy effect as they contain added preservatives that can also form NOCs.
Interesting to note that eating lots of green-coloured vegetables may lower colorectal cancer risk. The reason for the cancer-protective effect of our green friends could be from the green molecule which is central to the process of photosynthesis. Chlorophyll is very similar in structure to the animal haemoglobin molecule. Chlorophyll may compete with haemoglobin or help eliminate it from the body before it has a chance to be converted into NOCs.
A second culprit could be the actual cooking process of red meat itself, especially grilling or barbecuing at high temperature. The cooking causes char to form, which promotes the formation of heterocyclic amines (HCAs) on the surface of the meat. These HCAs have been shown to increase cancer risk. One way to reduce the formation of these compounds is to marinate the meat first. (Think of it as a protective layer on the meat.)
Yet another theory is that the iron in meat could be a candidate for causing cancer. Iron is needed for a host of health reasons, but too much of it can place a higher oxidative stress (a process not unlike “rusting“) on the body, and damage cells lining the large bowel.
When it comes to diet and cancer, it should be no surprise that fruits, vegetables and wholegrains come out on top as being the best cancer-preventing foods. Physical activity is now also recognised as a potent “cancer-preventing” habit. Estimates link regular physical activity to a 20–40 percent lower risk of colorectal and post-menopausal breast cancer, and a potential benefit in lowering prostate cancer risk too.
In addition, of course, to its cancer prevention benefit, physical activity plays a large part in preventing heart disease and diabetes, so the health benefits are multiplied.