I imagine that our ancient ancestors celebrated when they discovered that cooking, drying, and salting meat made it last longer, taste better, and reduce the probability that it could poison them. Win-win-win, right? The question of whether this processed meat could cause cancer later in life wouldn’t have occurred to people whose main food problem was not getting enough, and whose life expectancy was often only around 30 years.
These days, however, the risk-benefit profile of processed meat is different, especially for people in the industrialized world. Statistically, you’re likely to be alive well into your 70s (or if you’re already in or past your 70s, into your 80s or 90s). And your biggest challenge isn’t getting enough calories but refraining from consuming too many — and the wrong kind.
There’s a lot of research showing that what you eat is a huge determinant of your health. Some types of foods promote health, while others tend to lead to disease. One of the latter that’s garnered a lot of attention — from scientists, public health advocates, and foodies alike — is processed meat.
Many international health organizations have issued guidelines recommending that you limit or even eliminate processed meat from your diet, citing evidence that it can cause cancers, particularly those of the colon or rectum.
Meanwhile, others have asserted that processed meat poses little or no risk.
So what’s the truth about processed meat and cancer? Should you be concerned? And what about plant-based alternatives to hot dogs, bacon, and cold cuts? Are they any better for you?
Let’s find out.
What Is Processed Meat?
What are we talking about when we refer to processed meat? There’s no universal definition; after all, killing an animal, cutting it up, and cooking it is technically a form of processing. To help us out, the World Health Organization (WHO) has defined processed meat as meat that has undergone “salting, curing, fermentation, smoking or other processes to enhance flavour or improve preservation.” (Yes, spellcheck, that really is how to spell “flavor” in British English!)
Examples of processed meats include sausages and hot dogs, jerky, canned meats, deli meats and cold cuts, bacon, smoked fish, and other meat. For our purposes, we can also include in that category ultra-processed foods that contain meat, such as fast food, many frozen meals, and meat-based sauces.
Do Processed Meats Cause Cancer?
Over the past couple of decades, a number of population studies suggested a causal relationship between red and processed meat and cancer. Based on this evidence, in 2014 the WHO’s International Agency for Research on Cancer (IARC) prioritized the evaluation of these types of meat as part of its Monographs Programme. (A monograph is a long article or short book on a topic, as opposed to a monogram, which is someone’s embroidered initials. But I digress.)
After the IARC researchers thoroughly reviewed the scientific literature on possible links between meat and cancer (over 800 studies), they reported that red meat was a Group 2A carcinogen, while processed meat was a Group 1 carcinogen.
What does this mean? Well, the IARC has four food classes based on the probability of it causing cancer:
- Group 1 — carcinogenic to humans
- Group 2A — probably carcinogenic to humans
- Group 2B — possibly carcinogenic to humans
- Group 3 — carcinogenicity not classifiable to humans
For perspective, other Group 1 carcinogens include tobacco and asbestos. That’s not to say that processed meat increases your cancer risk to the same degree, but rather that the evidence of a causal link is equally strong. (That is, it’s not accurate to say that processed meat is “as dangerous” as asbestos just because they’re part of the same group.)
However, processed meat earned that rating based on evidence that it causes colorectal cancer, in particular.
The Research on Processed Meat and Colorectal Cancers
Let’s not just take the WHO’s word for it, though, and instead look directly at the evidence. What does the research actually say about processed meat and colorectal cancers (which we’ll abbreviate as CRC)?
Two very large cohort studies followed 87,000 female nurses and 47,000 male health professionals for decades. The participants reported on what their diets consisted of, and other lifestyle factors, in addition to their health status over time. A 2015 meta-analysis of these studies found that processed meat was positively associated with CRC risk. (In this case, “positively” doesn’t mean “in a good way;” instead, it means that the two increased or decreased together.)
A 2021 systematic review and meta-analysis of 148 published articles found that processed meat consumption was associated with a 6% greater breast cancer risk, an 18% greater colorectal cancer risk, a 21% greater colon cancer risk, and a 22% greater rectal cancer risk.
Based on these and similar studies, researchers in Germany ran a simulation to see how cutting back on processed meat would affect the incidence of CRC. They found that if everyone in Germany reduced their consumption of processed meat by one or two servings per day, on average, the country would expect 68,000 fewer CRC cases per year!
Cancer-Causing Components in Processed Meat
So what is it about processed meat specifically that can lead to cancer formation? How is it different from other kinds of meat that show less of a clear association with the disease?
Excess Sodium
There’s good evidence that too much sodium can lead to both gastrointestinal and colorectal cancers. And most people consume too much sodium. Worldwide, the average person is getting almost 4,000 milligrams per day, which is about double the recommended upper limit.
While processed meat and fish products differ greatly in sodium content across different food subcategories and in different countries, they tend to be higher than other meat products. This makes sense, as one of the main ways of preserving meat is by curing it in salt or brine.
In what must have been one of the world’s largest shopping sprees, an international team of researchers bought and assessed the sodium content in 26,500 prepackaged meat and fish products from China, the UK, Australia, South Africa, and the US.
They found that the products from China and the US had the highest concentrations of sodium: 1,050 mg per 100 g in the former, and 655 mg per 100 g in the latter. To put this in perspective, one common hot dog brand weighs in at 57 g per hot dog and delivers 560 mg of sodium.
Preservatives (Nitrates and Nitrites)
Nitrates and nitrites are chemical compounds that occur naturally in some plant foods and are also in processed meats. But your body treats them differently depending on the source. It converts the ones from fruits and vegetables into nitric oxide (“NO” — which is good, unlike a positive association between processed meats and cancer risk, which is bad). NO can promote cardiovascular, gastrointestinal, immune, and brain health, among other benefits.
But when nitrates and nitrites are used as preservatives to cure meat, they become a problem. Whether naturally occurring in meat or created synthetically and added, your body turns them into nitrosamines. These are known carcinogens that can cause DNA damage.
Nitrates and nitrites are normally combined with sodium when used as preservatives — that’s what “sodium nitrate” and “sodium nitrite” refer to in ingredient lists — which also contributes to the formation of these compounds.
One way high dietary levels of sodium nitrate or nitrite can contribute to cancer formation is by increasing the risk of methemoglobinemia, which is a very long word that is much less fun than “supercalifragilisticexpialidocious.” Methemoglobin (pronounced “met hemoglobin”) is a form of hemoglobin that isn’t able to carry oxygen. And methemoglobinemia just means that you have too much of that kind of hemoglobin. It’s thought that the cells’ lack of oxygen may contribute to tumor growth.
What About Plant-Based Nitrates and Nitrites?
Some processed meats, such as summer sausage and bacon, are “uncured,” and don’t use sodium nitrates or nitrites. However, that term is misleading. Instead of not using any preservatives at all, these products often use nitrites from plants like celery. Yet many processed meat purveyors market their products cured with celery powder as “nitrite free.”
That sounds great until you realize that there’s little evidence that preserving meats using nitrites from celery is any healthier than preserving them using added nitrites from other sources. And while sodium nitrite content is regulated by the United States Department of Agriculture, nitrites from celery powder are not.
While vitamin C and the phytochemicals in vegetables and fruits could theoretically reduce the risk of nitrosamine production, they’re probably overmatched by the presence of all the harmful compounds found in processed meat.
So what are those harmful compounds?
Polycyclic Aromatic Hydrocarbons (PAHs)
PAHs are environmental pollutants that form when foods rich in carbon are cooked at high temperatures, such as with smoked meats. The highest levels are in foods that also contain a lot of fat.
Certain PAHs have been found to cause cancer in laboratory animals (our view on the use of animals in medical research is here). And the IARC has classified two of them — benz(a)anthracene and benzo(a)pyrene — as probably carcinogenic to humans as well. (This research goes back a long way and originally looked at occupational exposure instead of diet. For example, a 1775 treatise by the English physician Percival Pott attributed the high rates of scrotal cancer in chimney sweeps to their exposure to soot.)
Insulin-Like Growth Factor (IGF-1)
IGF-1 is a hormone that helps control the growth and development of organs, muscles, and tissues in the body. It’s crucial for health and growth, but having too much of it can negatively affect your health. Excess IGF-1 can, among other things, lead to tumor progression and increased risk of cancer.
Foods that are high in protein raise IGF-1 levels in your body, essentially telling your cells to grow. And cancer cells are highly receptive to that message. Animal protein, in particular, raises IGF-1 levels the most because the proteins in animals are similar to the ones you produce yourself.
While increased levels of IGF-1 aren’t uniquely caused by eating processed meats, they’re still a contributing factor to consider when evaluating potential cancer-causing components.
Dietary Guidelines and Recommendations for Processed Meat
Clearly, processed meat isn’t a health food. But how bad is it really? How much effort should you expend to avoid it? Can you still be healthy while having hot dogs, jerky, and bacon on a regular basis?
We know that there’s a dose-response thing going on — that is, the more processed meat you consume, the higher your risk of developing cancer. The WHO (that’s a callback to the World Health Organization, not the guys who sing “Behind Blue Eyes”) estimates that every 50-gram portion of processed meat you eat per day increases your risk of CRC by about 18%. And 50 grams, which is just under two ounces, is what you’d get from a bun-length hot dog or 6 slices of bacon.
Based on these and other findings, many national health recommendations advise people to limit or eliminate their intake of processed meat. The IARC report did not find a “safe level” of processed meat.
The American Cancer Society website advises, “A healthy eating pattern limits or does not include red and processed meats,” while the Canadian Cancer Society is more forthright, recommending that people avoid processed meats altogether. Towards the other end of the spectrum, the World Cancer Research Fund International’s Cancer Prevention Recommendation for processed meat states, “Eat little, if any.”
Are Processed Plant-Based Meats a Healthier Option?
Since Worthington Foods first released its soy-based “Veja-Link” meatless wieners in 1949, many other companies have entered the plant-based processed meat alternative market. And lately, they’ve become much more “meat-like” in terms of both flavor and texture.
It’s no secret that a plant-based diet can be healthier for people, animals, and the planet. But are the processed plant-based meat analogues really healthier than the animal products that inspired them?
The answer is probably yes, followed by a pretty big “but.” (Note to self: Be a grown-up, and don’t make a joke here.)
On the upside, plant-based processed meats contain fiber (albeit a smaller amount than if you just ate the whole foods they come from), which “real” meat doesn’t have. Fiber can help prevent some cancers, including colorectal ones, by sweeping carcinogens out of your digestive tract quickly.
Plant-based meats replace animal protein with plant-based sources like legumes. These proteins don’t form harmful compounds in your body (like those PAHs and nitrosamines we mentioned earlier).
Overall, meat analogues made from plants also have a healthier nutritional profile than processed meats.
And here’s the big “but:”
Plant-based meat alternatives are still highly processed. They may still be high in sodium and contain refined oils, sugar, and other additives or GMO ingredients. If you have a hankering for meat alternatives, you have a number of options that can benefit your health (rather than just damage it less). Some stellar whole-food meat substitutes include mushrooms, beans, lentils, tofu, tempeh, and jackfruit.
There are numerous studies that show that swapping meat for foods like mushrooms or legumes is good for your health.
And additional studies show that these foods can actually lower your colorectal cancer risk, specifically. I have to mention one of the studies just because it has such an awesome name: “The Study With Appetizing Plantfood — Meat Eating Alternative Trial” — SWAP-MEAT for short.
For a collection of recipes to help transition from meat eating to plant-based meat eating, check out this article: From Beef to Beets: Plant-Based Recipes for Meat Lovers.
There IS a Link Between Processed Meat and Colorectal Cancer
The relationship between processed meat and colorectal cancer is a matter of growing concern as more and more scientific evidence sheds light on the risks. These foods contain a cocktail of harmful compounds that can contribute to colorectal cancer risk, leading many national and international health organizations to recommend limiting or eliminating processed meats entirely.
Plant-based meats are a good alternative that may reduce cancer risk — but they are still processed foods and should be used in moderation or to help transition to a whole foods, plant-based diet.
Needless to say, what you put on your plate can have a profound impact on your health and your odds of contracting chronic diseases like colorectal cancer.
Tell us in the comments:
- Have you tried any plant-based processed meat analogues?
- What whole plants have you tried that you can substitute for processed meats in recipes?
- What’s one small dietary shift you can make to get more fiber on your plate?
Featured Image: iStock.com/Karaidel
