Processed Meats Declared Carcinogenic

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Story at-a-glance -

  • The International Agency for Research on Cancer, a part of the World Health Organization, has classified processed meats as a Group 1 carcinogen, as the evidence strongly shows it can cause colorectal cancer in humans
  • Cooked red meat was classified as a 2A “probable human carcinogen,” with limited evidence suggesting it may raise your risk of colorectal, pancreatic, and prostate cancer
  • Recent tests reveal three percent of hot dog samples contained pork that was not listed as an ingredient on the label; 10 percent of vegetarian hot dogs also contained meat

By Dr. Mercola

It's well-established that food processing and food additives can create health hazards, and processed meats are no exception. Processed meats are those preserved by smoking, curing, salting, or the addition of chemical preservatives.

This includes bacon, ham, pastrami, salami, pepperoni, hot dogs, some sausages, and hamburgers (if they have been preserved with salt or chemical additives) and more.

Previous studies have linked processed meats such as sausages, hot dogs, and sandwich meats to an increased risk of cancer, male infertility, and early death.

For example, a 2007 analysis1 by the World Cancer Research Fund (WCRF) found that eating just one sausage a day may raise your risk of bowel cancer. Specifically, 1.8 ounces of processed meat daily – about one sausage or three pieces of bacon – was found to raise your likelihood of the cancer by 20 percent.

The American Institute for Cancer Research2 (AICR) has long recommended avoiding processed meats entirely for this reason.

The institute explicitly warns that that "there is no safe threshold" for eating processed meats. It also recommends limiting red meat to a maximum of 18 ounces per week, to avoid raising your risk for colorectal cancer.

Processed Meats Now Classified As Group 1 Carcinogen

After reviewing some 800 studies, the International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), also recently concluded that processed meat can cause colorectal cancer in humans,3,4,5,6,7,8,9 classifying it as a Group 1 carcinogen.

As reported by Reuters:10

"IARC classified processed meat as 'carcinogenic to humans' on its group one list along with tobacco and asbestos, for which there is 'sufficient evidence' of cancer links.

Each 50-gram (1.8-ounce) portion of processed meat eaten daily increases the risk of colorectal cancer by 18 percent, the agency estimated.

A 50-gram portion would be the equivalent of eating one hot dog or two slices of bacon. Americans eat about 21.7 grams of processed pork per day, according to a 2011 National Health and Nutrition Examination Survey."

According to Dr Kurt Straif, a member of the IARC panel:

"For an individual, the risk of developing colorectal (bowel) cancer because of their consumption of processed meat remains small, but this risk increases with the amount of meat consumed."

Cooked Red Meat Classified As Probable Human Carcinogen

Cooked red meat (which the IARC identifies as beef, lamb, and pork even though many food specialists consider pork a "white" meat) was classified as a 2A "probable human carcinogen," with limited evidence suggesting it may raise your risk of colorectal, pancreatic, and prostate cancer.

While glyphosate and other toxic pesticides are in this same category, it's important to realize that the IARC's classifications of carcinogens are based on strength of evidence, not degree of risk.

So while processed meats are in the same category as smoking and asbestos, and red meats are lumped in with pesticides, the degree of risk is NOT identical.

For comparison, the IARC estimates high-meat diets may be responsible for 50,000 cancer deaths per year worldwide, whereas smoking is associated with 1 million cancer deaths each year, alcohol with 600,000 deaths, and air pollution with 200,000.

As noted by David Wallinga, senior health officer for the Natural Resources Defense Council:

"Nobody is telling people not to eat meat. What they're saying is if you eat it, eat less of it and buy it from sources that have produced it better."

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Your Gut Health May Play a Significant Role in Your Cancer Risk

I agree with Wallinga's statement, as part of the problem is likely due to the way the meat was raised. Chris Kresser L.Ac, a licensed integrative medicine clinician, recently wrote an article11 in which he analyzes a number of studies looking at red meat and cancer.

He notes that while your gut microbiome appears to have a significant influence on your cancer risk, this has rarely been addressed in these kinds of studies.  The consolidation of processing plants has resulted in a handful of massive slaughterhouses that process hundreds of animals per hour, touched by hundreds of different employees.

Many opportunities exist for contamination when so many animals (harboring antibiotic resistant bacteria) pass the same equipment and are handled by so many workers.   These bad bugs are big contributors to illness, and play a huge role when reviewing any meat related study on human health.

When it comes to CAFO meats and processed meats, the latter of which contain a number of potentially harmful food additives, the cancer link may actually be due to the way such meats impact your gut flora.

We also know that glyphosate can have a significantly detrimental impact on healthy gut bacteria, and CAFO animals are typically fed grains contaminated with glyphosate. This affects not only the animals' health, but your health as well.

According to Kresser:

"We still have a lot to learn about the influence of the microbiome on health and disease, but we know enough already to conclude that it is significant.

It is possible — and I would argue likely — then, that the variability we see in studies showing an association between red meat consumption and cancer may be in part due to the status of the patient's microbiome.

In other words, a patient with a dysbiotic (i.e., compromised) microbiome may be at increased risk for cancer if he or she consumes high amounts of either fresh or processed red meat. But a patient with a normal, healthy microbiome may not be."

Award-winning food politics writer Tom Philpott pointed out a similar angle in a recent Mother Jones article,12 stating that:

"[The IARC] acknowledges that 'it is not yet fully understood' why red meat or processed meat consumption seems to boost colorectal cancer rates, though it mentions that both contain potentially carcinogenic chemicals that form during meat processing or cooking, like nitrite-related compounds in stuff like bacon and hydrocarbons in cooked meat. Susan Gapstur, the vice president of epidemiology for the American Cancer Society, told me that these compounds can lead to 'oxidative damage in the gut,' leaving us vulnerable to cancer."

How Processing and Cooking Meat Raises Cancer Risk

I firmly believe that some animal protein is important for health, but there are some caveats. The way the animal is raised – what the animal eats, where it lives, the drugs it is given, and whether it has access to the outdoors – make a major difference in whether it's a healthy food or a disease-promoting one. When it comes to meats, I recommend eating organically-raised grass-fed meats only that are also pasture-finished, not grain-finished.

The second factor that can make a big difference in its health potential is how the meat is prepared and cooked. As noted by the AICR,13 and recently recapped by Time magazine,14 these are some of the ways in which processed meats may increase your cancer risk:

  • The processing of meat often involves nitrites that may form cancer-causing N-nitroso compounds
  • Processing may also involve:
    • Smoking, which leads to formation of cancer-causing PAHs
    • Adding high amounts of salt, which may promote stomach cancer
  • Heme iron found in processed red meat may also pose a cancer risk, as it too breaks down into carcinogenic N-nitroso compounds in your digestive tract15

Cooking meat at high temperatures (and this applies to both processed meats and unprocessed meats like steak) also produces a number of toxic end products, including:16 

  • Heterocyclic amines (HCAs), which begin to form at 212 Fahrenheit (100 degrees Celcius). The most toxic HCAs start forming at around 572 degrees F (300 C). This is why grilled and charred meats are among the most hazardous. Meat cooked at high temperatures can contain as many as 20 different kinds of HCAs, which have been linked to cancer. The worst part of the meat is the blackened section, which is why you should always avoid charring your meat and never eat blackened sections
  • Polycyclic aromatic hydrocarbons (PAHs)
  • Advanced glycation end products (AGEs) — one of the major molecular mechanisms whereby damage accrues in your body, which leads to disease, aging, and death
  • Acrylamide, a cancer-causing and potentially neurotoxic chemical

As a general rule, the longer the meat is cooked and the hotter the temperature, the more HCAs and PAHs are formed. Grilling and frying create the highest amounts of toxic end products, whereas cooking methods using indirect heat, such as stewing, steaming, braising, or poaching, create the least amounts.

Should You Give Up Bacon?

Bacon specifically has come under repeated attack for a number of reasons. First, it's loaded with saturated fat, which has long been wrongly demonized. This is NOT a valid health reason to avoid bacon, in my view. However, pork is also known to be more prone to contamination with pathogenic microbes, and this is a very real health threat. Third, when pork is cured (most bacon is cured, unless labeled otherwise), the issue of nitrates raising your cancer risk becomes a real concern.

While I have cautioned against the consumption of pork in the past — primarily due to the risk of contamination — I am not anti-pork, or anti-bacon, per se. My main concern about pork is that you need to be cautious about the source of the pork you consume — just as you should be cautious about the source of your beef, eggs, and poultry. If your pork is pasture-raised and the pigs live in their natural setting eating pig-appropriate food, then pork can certainly be a nutritious part of your diet. Once it is properly raised it should also be preservative (primarily nitrates) free.

Pork is arguably a healthy meat from a biochemical perspective, and if consumed from a humanely raised pastured hog like those on Polyface Farm and prepared properly, there is likely minimal risk of infection. However, virtually all of the pork you're likely to consume will not fit these criteria — it is extremely difficult to find.

This doesn't mean you have to avoid it entirely, but you may want to consider limiting the amount of bacon you eat on a weekly basis, and avoid crispy bacon.

Other Startling Food News: 10 Percent of Vegetarian Hot Dogs Contain Meat

In related news,17 a food fraud investigation by the food analytics group Clear Labs18 revealed that some processed meat products may not be what you think they are... After analyzing 21 vegetarian hot dogs using novel molecular testing and genetic sequencing, 10 percent of them were found to contain meat. Two percent of the samples also contained human DNA, thought to be caused by hygiene problems somewhere along the manufacturing process. Although not specified, this likely refers to contamination with human hair, which is quite common in food processing.

In all, the group tested a total of 75 different brands of hot dogs and sausages, and found problems with more than 14 percent of the samples. Some of the most common problems included the following:

  • Inaccuracies on the nutritional label
  • About three percent of the samples contained pork that was not listed as an ingredient on the label
  • Other unexpected and unlabeled ingredients, such as chicken and lamb, were also found

As reported by CNN:19

"[Professor Melinda Wilkins, who specializes in food safety, said] 'The whole issue of food adulteration is starting to become a really hot area right now, and I think a lot of people became aware of the issue in meat fairly recently,' she said, referring to the horse meat found in hamburgers in Britain in 2013.

'A lot of times, food adulteration issues are not a food safety concern necessarily, but still it's disturbing to think that you might be eating something that you're not aware of,' she added. 'So I think companies will want to be very careful about how they label, and they may want to be doing more testing of their suppliers.'"

Three Factors to Consider for Safe Meat Consumption

I believe that while the risks of processed meats and cooked red meats are real, these risks can be mitigated. After all, meat does have valuable nutritional benefits — it's not like smoking that has zero health benefits. The key is to consider the quality and quantity of the meat, and the way you cook it.

  • First of all, Americans tend to eat far more meat than required for optimal health. There are a number of reasons why I believe it's prudent to limit your protein intake. The first is that if you eat more protein than your body requires, it will simply convert most of those calories to sugar and then fat. Increased blood sugar levels can also feed pathogenic bacteria and yeast, such as Candida albicans (candidiasis), as well as fueling cancer cell growth.

    Excessive protein can also have a stimulating effect on an important biochemical pathway called the mammalian target of rapamycin (mTOR). This pathway has an important and significant role in many cancers. When you reduce protein to just what your body needs, mTOR remains inhibited, which helps minimize your chances of cancer growth.

  • Second, most people eat too much poor quality CAFO meat. I recommend eating only organically-raised grass-fed or pastured meats, and this includes beef, chicken, turkey, lamb, and pork. There are a number of reasons to heed this recommendation. Organic pastured meats tend to have a better nutritional profile, have far lower risk of pesticide contamination, and a reduced risk of contamination with drug-resistant pathogens. Organic farming also benefits the environment, promotes food security, and creates a more sustainable food system.
  • Third, there are ways of cooking your meat to minimize health hazards. Grilling and frying create the highest amounts of toxic end products — the most toxic parts being the charred or blackened portions. Cooking methods using indirect heat, such as stewing, steaming, braising, or poaching are the safest, as they create the least amounts of toxic end products. 

To summarize, look for nutrient density and not quantity - that is the true value of any food.   Eat less of higher quality foods, and prepare them slowly with care to realize their maximum value.