Eating processed meat can increase your risk of getting colorectal cancer. The World Health Organisation’s International Agency for Research on Cancer (IARC) says that each 50g portion of processed meat eaten daily (about two bacon rashers) increases bowel cancer risk by 18%. But before you give up processed meats forever, read on.
There are three main cancer-causing agents in processed meat: iron, which occurs naturally in meat; N-nitroso, which forms when meat is processed; and MeIQx and PhIP, which are chemicals formed during cooking.
Iron is found in all meats. It is easily absorbed by the body and is an important part of our diets. Excess amounts, however, can increase the risk of cancer by acting as a catalyst for the formation of free radicals. As with many things – sunshine, salt, fats – the poison is the dose.
N-nitroso compounds only occur if the meat contains added nitrite or nitrate salts. The richest food sources of N-nitroso compounds in the US are bacon, luncheon meats, sausage and hot dogs. However, the second highest food source is from fresh and smoked seafoods. Low to moderate sources include grains, dairy, oils, liquor and wine which means we are exposed to these chemicals through many non-meat food sources as well.
Although MeIQx and PhIP form during cooking, the concentration of these chemicals depends on the cooking method and how well the meat is cooked.
From bresaola to nitrate-filled bangers
But not all processed meats are the same, so the cancer risk can vary considerably depending on which product you’re talking about. For example, dried meat products such as bresaola or biltong are simply the result of drying lean meat in natural conditions or in an artificially created environment. Many of the nutritional properties, in particular the protein content, remain unchanged through drying.
Compare this with precooked-cooked meat products which contain mixes of lower-grade muscle trimmings, fatty tissues, head meat, animal skin, blood, liver and other edible slaughter byproducts. The first heat treatment precooks the raw meat and the second heat treatment cooks the finished product at the end of the processing stage. As you can see, these are two very different products.
Unfortunately, the IARC report did not provide details of the risk of cancer associated with the different types of processed meat, as this data is not available. This important fact was either missed or deliberately under-reported by many in the media. Eating processed meat should not be considered an unhealthy pastime, but choosing the type you eat and how it is cooked is very important.
Some sausage manufacturers, do not include any of the nitrites or nitrates which should be avoided. Selecting products with the highest content of meat with only seasonings or plant food ingredients added (some now contain half meat, half vegetable protein) is prudent and not overcooking your meat is really important. The cancer causing chemicals formed during cooking vary dramatically depending on how well you cook your meat and the cooking method. For example, a very well done steak will contain between five and 10 times more MeIQx and PhIP than a medium cooked steak.
Eating processed meats which do not contain nitrates or nitrites and cooking it correctly is not the unhealthy option that some portray it to be and is fine as long as it is done in moderation (no more than 70 grams per day of red meat and processed meat), and as part of a well-balanced diet.
About The Author
Chris Elliott, Professor of Molecular Biosciences, Queen's University Belfast
Marie Cantwell, Senior lecturer, Queen's University Belfast