Processed meats are often publicised to be as bad as smoking. Thankfully, you are not doing the same harm as a cigarette every time you reach for that charcuterie board, but it is definitely far from harmless. Is this the end of the Christmas ham?
Processed meat is any meat that has been changed or preserved. Processes such as curing, salting, canning, smoking and the addition of preservatives all create processed meat products. Examples of processed meats include bacon, ham, chicken loaf, luncheon meat, salami and any kind of sausage. Broadly speaking, it also includes pâté, jerky, corned beef, chicken nuggets and even smoked fish.
The bad news: There is irrefutable evidence that processed meats are associated with increased colorectal cancer risk. The misconception that processed meats are equivalent in harm to smoking largely stems from the fact that the World Health Organisation has classified it as a Group 1 carcinogen; these are substances where there is convincing evidence that demonstrates cancer-causing ability in humans. For context, other Group 1 carcinogens which are regularly consumed in various places across our world are tobacco, alcoholic beverages, Betel or areca nut.
Sadly, colorectal cancer is the 3rd most commonly diagnosed cancer for Australian men and 2nd after breast cancer for Australian women. Globally, colorectal cancer is the third most common cancer but is the second most deadly. Long-term evidence has shown increasing wealth in a population leading to shifts towards sedentary lifestyles and increased consumption of animal-source foods match the increase in colorectal cancer incidence.
You might want to rethink that. There is global consensus that there is no safe level of processed meat consumption. The American Institute for Cancer Research suggests that consuming as little as 50g of processed meat a day increases the risk of colorectal cancer risk by 18% compared to someone who consumes no processed meat. 50g is a single slice of thinly shaved ham. That’s it. There is also a strong dose-response relationship when it comes to the consumption of processed meats and the risk of cancer or death cancer or death from cardiovascular disease. So if you were to consume two slices of leg ham in your sandwich every day, that’s potentially a 36% increased colorectal cancer risk. Very risky sandwiches! A meta-analysis published in Public Health Nutrition which summarised multiple studies encompassing over 1.1 million study participants, 35,000 cardiovascular events, 125,000 all-cause deaths and 45,000 cancer deaths found that consuming processed meats was associated with a 15% increased risk of death by any cause, 15% high risk of death caused by cardiovascular disease and an 8% increased risk of death by any cancer.
But what does this all mean when it comes to our own lives? Talking about risk as percentages can be confusing and unfamiliar. Well, that two slices of ham you just consumed? That’s potentially 36 minutes of a healthy, good-quality, disease-free life, gone. Just like that sandwich… and that’s not even talking about death, that’s just losing a good quality of life and being disease-free. Maybe reconsider that add-on bacon altogether when brunching at the cafe. Substituting just 10% of your total caloric intake away from processed meats to fruits, vegetables, nuts, legumes or sustainable, minimally processed seafood can give you back 48 mins of your life. Maybe Super Mario’s creators were onto something with the 1-Up Mushroom.
Indeed, meat preservation using methods such as salt-curing, smoking, drying, fermenting or any combination of these has been in recorded history since at least 1500 BCE. Meat is a valuable protein source and with no mechanical refrigeration meant our ancestors out of necessity had little choice but to develop ways to preserve meat. For people in reasonably developed countries, food supply chains are reasonably robust in supplying fresh or minimally processed produce safely and reliably. Most of us consume processed meats for culinary delight and convenience. The curing process has lost its relevance to prevent our households from going hungry between harvests or dying from microbially contaminated meat. While curing does prevent food-borne diseases like botulinum currently, with what the risks we know about and the alternatives we have, eating processed meat does seem unnecessarily risky.
Processed meats are bad because they are rich in the haem molecule, found in myoglobin, red blood cells and in cytochrome, an iron-containing protein in cells. When meat is digested, it produces a soup of amino acids (nitrogen-based molecules), the breakdown products of haem and fats. Haem’s breakdown products alone are toxic to our gut cells and are known to be carcinogenic. These very same products also have strong oxidative potential and cause a fat oxidation chain reaction which creates free radicals thus increasing oxidative stress on gut cells which also leads to cellular and DNA damage and are cancer-inducing. To add salt to the wound, some of the haem breakdown products also react with broken amino acid chains to form N-nitroso compounds. These compounds are known carcinogens and are particularly damaging to the cells in the bowel lining. And this is actually just for red meat alone! We haven’t introduced the negative impacts of nitrites used to make the meat deliciously pink and tasty!
Nitrites such as sodium or potassium nitrite are added as preservatives in many cured meats. These increase the production of N-nitroso compounds in the gut and, yup, you guessed it, reacts nicely with haem’s breakdown products to pump out even more of these carcinogenic molecules. Finally, processes like smoking or charring meats over high temperatures (roasting, charcoal or grilling) produces a broad class of compounds called polyaromatic cyclic hydrocarbons (PAH). They form through complex chemical reactions mediated by heat and smoke. PAHs are known carcinogens but we don’t know exactly how they affect cancer risk in individuals.
But hold on, beetroot and many vegetables are rich in nitrogen compounds and nitrates. Nitrates have a different oxidation state (note the ‘A’ instead of the ‘I’ in nitrate). Not only do vegetables lack heam and the fats, the nitrates are chemically different and actually reduce certain cancer risks and cardiovascular risks.
Perhaps reconsider rushing out to replace that bacon or turkey loaf with a plant-based analogue. Many commercially available plant-based meat substitutes are considered ultra-processed foods. The Institute of Food Technologists highlight that there are no long-term studies evaluating the health effects of consuming plant-based meat alternatives. In fact, some of these substitutes have higher saturated fat contents than their comparable meat counterpart, while certain plant compounds have antinutritive effects which could reduce the body’s ability to absorb certain minerals. Some products even contain added haem which could still have the same negative effects as regular meat, but we don’t know for sure. Plant-based meat alternatives are reported to be less carbon-intensive, but the magnitude of this benefit is clouded because it is difficult to measure and many manufacturers of meat substitutes keep their production methods secret or do not report the full picture.
Yes, not all processed meats are created equal, and some might carry less risk However, given what we know, it is best to avoid processed meats altogether. Also, reducing consumption of red meats will help you stay healthier; follow what is recommended for your age, sex and life stage according to the Australian Dietary Guidelines. If you really need that Christmas ham, eat sparingly and co-consume it with plenty of fresh vegetables, plant fibre and fruits. The fibre and antioxidant compounds in fresh vegetable, fruit and whole grains can bind some of the toxic compounds created or prevent their creation to a small extent. Michael Pollan, author of In Defense of Food puts it succinctly, “Eat food. Not too much. Mostly Plants.”
Dr David Chua is a Research Fellow at Healthy Primary Care, Menzies Health Institute Queensland, Griffith University. His interests are health equity, primary care systems innovation, utilising primary care data pragmatically to improve outcomes and improving lifestyle prevention in primary care.
David’s background is in food science and nutrition. His past projects include multicultural healthcare coordination, end-of-life care, person-centred care, the role of medical receptions in the healthcare system and community lifestyle prevention.
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