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Does Eating Meat Really Cause Cancer?

People all over the world have been wondering whether or not they should limit their consumption of processed and red meat, after reading the conclusions of the International Agency for Research on Cancer (IARC) last fall. In October 2015, the IARC, the World Health Organization’s cancer agency, released a statement classifying processed meat as carcinogenic to humans and red meat as a probable carcinogen.[1] However, the statement raises a variety of questions that remain unanswered – and that may ultimately show that the blanket condemnation of all such meats is unwarranted.
The IARC’s working group, consisting of 22 scientists from ten countries, reviewed more than 800 epidemiological studies worldwide investigating the association of processed and red meat consumption with cancer. They concluded that there was “sufficient evidence” for the carcinogenicity of processed meat in humans. Risk was seen to generally rise with the amount of processed meat consumed, and analysis of ten studies found that “every 50 gram [1.76 ounce] portion of processed meat eaten daily increases the risk of colorectal cancer by about 18%.” An association between processed meat and stomach cancer was also noted, although the evidence was considered inconclusive.
The group of experts also found “limited evidence” in humans for an increase in colorectal cancer risk from eating red meat, although chance, bias, and confounding – such as from other dietary or lifestyle factors – could not be ruled out with the same degree of certainty as in their finding on processed meat.[2] Although the carcinogenicity of red meat was not established, data indicated that if the link was found to be causative, colorectal cancer risk could increase “17% for every 100 gram [3.5 ounce] portion of red meat eaten daily.”[3] The data also showed associations between red meat consumption and pancreatic and prostate cancer, although evidence for this was weaker. Despite all this, the IARC acknowledged the nutritional value of red meat, advising people to limit its consumption rather than completely eliminate it from the diet.
The IARC defines processed meat as “meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation.” Red meat refers to the unprocessed muscle meat of any mammal, such as a cow, deer, pig, lamb, horse, or goat. However, the reasons these meats may be cancer-causing remain unclear, and a number of potentially significant questions have not been explored. Are there differences in the inherent quality and potential carcinogenicity of meat raised in different ways? How does meat become carcinogenic when it is smoked, cured, salted, or fermented? Can different methods of preparation cause food to become healthier or more dangerous to eat? Although researchers may not have all the answers to these questions yet, understanding more about what goes into the food we eat will help us make better nutritional choices.
What does your food eat?
Meat has been an important part of the diet of many traditional cultures for millennia – without causing modern diseases such as cancer. However, the ways in which the animals live and the meat is prepared have changed over time, with significant changes taking place in the last half century. Until the 1960s, farmed animals were raised almost exclusively on pasture, grazing freely in their natural environment. Today, the majority of these animals survive on soy and cereal grains such as corn and wheat for most of their lives. But it turns out that grains are not suitable food for cows and other ruminants, and pigs need a far more varied diet than they have access to in mass-production facilities.[4,5] The consequences of animals eating a diet closer to that of birds and mice include reduced nutrient content of their meat, heightened levels of unfavorable compounds in their meat and fat,[6] and an overly acidic digestive environment,[7] causing health conditions that have resulted in the excessive administration of antibiotics and other medications, some of which may persist in the meat.
Much factory-farmed meat is also contaminated with pesticides, herbicides, and synthetic hormones, substances linked to various types of cancer.[8,9] The animals’ diet, their mothers’ health when they were in utero, their living environment, the amount of stress they encounter, and the disease prevention and treatment methods administered to them affect the quality of their meat. Almost all meat available in grocery stores, restaurants, and other food distributors comes from animals fed an unnatural diet while being raised in unhealthy and inhumane living conditions. It would be extremely helpful to know the particulars of the meat utilized in the studies analyzed by the IARC, but this information either is not available or has not been released.
Of particular interest are the health effects of grassfed versus grainfed meat – a subject not addressed in the IARC statement. Studies show that pasture-raised meat is much more nutritious than conventionally raised meat.[10,11] For one thing, meat and dairy from grassfed animals are prized for their high levels of conjugated linoleic acid (CLA), a potent anticarcinogen and antioxidant synthesized in the fat of animals, primarily ruminants.[12,13] Grassfed cattle have been shown to produce two to three times more CLA than those fed in confinement on high-grain diets.[12] One study found an inverse correlation between colorectal cancer in women and long-term consumption of high-fat (CLA-rich) dairy foods.[14]
Grassfed beef also has a healthier balance of essential fatty acids.[12] The mainstream Western diet is much higher in omega-6 fatty acids than omega-3s, a condition that contributes significantly to the development of inflammatory diseases, such as cancer.[15] Consumption of grainfed beef, with an omega-6 to omega-3 ratio averaging more than 7 to 1, contributes to this imbalance, while the ratio for grassfed beef – less than 2 to 1 – is beneficial.[12]
In addition, grassfed beef is higher in beta-carotene, a precursor to vitamin A; precursors to vitamin E; and the cancer-fighting antioxidants glutathione and superoxide dismutase (SOD).[12] Due to factors such as these, it seems reasonable to assume that grassfed and grainfed beef might have different relationships to cancer in humans, and it is hoped that future studies will investigate this.
The parts of the animals consumed could also conceivably make a difference. The IARC includes only muscle meat in their definition of red meat, reflecting common consumption patterns in Western society. Many people today eschew both organ meats and animal fats. However, this definition – and this practice – considerably narrows the range of nutrients available from the meat. In comparison, many traditional cultures wasted almost no parts of the animals they hunted or raised. It would benefit us to follow their examples, as the fat and organs of properly raised animals have proved to be the most healthful parts, providing vitamins, minerals, and other nutrients that are easily used by the body and can help improve the bioavailability of nutrients from other foods.[16] Avoiding good-quality organ meats and animal fat may be contributing to widespread micronutrient deficiencies, which hinder the body’s ability to fight off or heal from infections and diseases, including cancer.
How is your meat processed?
Although the risk of an individual developing colorectal cancer from consuming processed meat is small, according to the head of the IARC Monographs Programme, the large number of people who consume it worldwide gives this issue importance.[1] In fact, the Global Burden of Disease Project estimates that annually about 34,000 deaths from cancer are attributable to diets high in processed meat.[3]
Unfortunately, the wide variety of foods the IARC groups together as “processed meat” reduces the usefulness of their conclusions. This category includes such diverse foods as hot dogs, ham, sausages, corned beef, beef jerky, canned meat, and even “meat-based preparations and sauces.” The ingredients of these foods vary widely as well, as they can include not only beef or pork but also “other red meats, poultry, offal, or meat by-products such as blood.”[3]
Some methods of processing meat result in the formation of carcinogenic chemicals, such as N-nitroso compounds (NOCs) and polycyclic aromatic hydrocarbons (PAHs).[2] However, the IARC states, whether differences in preservation methods affect cancer risk is “unknown.”This lack of information blurs the potentially important distinctions between industrially and traditionally processed meats.
Today, meats such as sausage and ham are typically preserved with mineral-deficient sodium chloride, or table salt (as opposed to naturally mineral-rich salts), along with nitrates and nitrites, which can form carcinogenic nitrosamines (a type of NOC) if heated at high temperatures.[17] However, there are many types of food processing other than those typically used by industrial food manufacturers. Meats and other foods have been marinated, salted, smoked, fermented, and aged using simple methods and ingredients by healthy traditional peoples throughout global history. Perhaps the ways our meat is prepared- and cooked- hold more significance to our health than many of us realize.
As for cooking, high-temperature methods, such as pan-frying or barbecuing, were of primary concern to the IARC, although the working group failed to reach a definitive conclusion as to their safety. These cooking methods cause chemical reactions in meat that can “contribute to carcinogenic risk.” [3] PAHs – known to be mutagenic – form in meat that has been smoked or cooked over an open flame or in direct contact with a heat source, although the IARC states that there is “little direct evidence” that DNA damage occurs following the consumption of meat.[2] Heterocyclic aromatic amines (HCAs), another group of mutagenic compounds, form in meat that is heated to high temperatures, particularly over 300° F.[18] Nonetheless, the working group stated that they did not have enough data “to reach a conclusion about whether the way meat is cooked affects the risk of cancer.” [3] Due to the presence of PAHs, it seems reasonable to conclude that charring meat over fire isn’t a good idea, although occasional barbecuing may not need to be completely avoided. However, cooking methods that do not involve direct contact with the heat source – such as roasting, baking, and boiling – may be advisable for more frequent meat preparation.
Marinating meat, a traditional preparation technique in many cultures, can help to reduce both PAHs and HCAs. Wine, beer, and apple cider vinegar are a few of the beneficial marinade ingredients that help promote natural fermentation processes in meat, which can improve nutrient quality and reduce formation of these potentially harmful cooking by-products.[19,20]
An interesting point is that cooking meat increases its concentration of the anticarcinogenic fatty acid CLA. For example, the CLA content in ground beef is increased almost fivefold after grilling.[13]]
What do you eat with your meat?
A well-rounded, high-quality diet is essential to preventing and fighting disease, and the way diverse foods work together may further these goals. For example, kimchi, sauerkraut, pickles, kefir, and other naturally fermented foods- all of which are rich in probiotics – can reduce gut inflammation and support the immune system.[21] Studies indicate that the presence of probiotics in the diet may help neutralize the mutagenic compounds formed in meat cooked at high temperatures and have an anticarcinogenic effect.[22-24] For these reasons, traditional societies’ consumption of fermented foods may have counteracted the potential adverse health effects from food cooked in direct contact with flames.[25]
Nutrients found in food from both plants and animals have the power to block and even reverse the growth of malignant tumors. Some cancer-fighting substances present in plant foods include curcumin (from turmeric) and resveratrol (from grapes). Adequate amounts of vitamin C[26] and calcium[27] can be protective against colorectal cancer. Restoring the body with beneficial bacteria, vitamins, and minerals – whether from food or supplementation – is vital for disease prevention and recovery, as well as maintaining good health.
Issues such as these were beyond the scope of the IARC review. However, various dietary and lifestyle factors need to be seriously considered in order to better understand the connection between diet and cancer. Did study participants eat high-meat diets or did they consume ample amounts of vegetables? Were they relatively active or sedentary? Did they experience high levels of stress or inflammation? All of these things influence a person’s health and can play a big role in whether or not they will be diagnosed with colorectal cancer (or any other disease, for that matter).
Cancer is a complex disease whose causes are not completely understood. There is much yet to learn about the possible contributions of the many new technologies and harmful eating habits prevalent throughout the world today. Eating red and processed meats was practiced by traditional peoples long before the current global cancer epidemic began. Perhaps we need to look more closely at how some things have changed, such as the addition of artificial preservatives and other chemicals to our meat and the presence of mass amounts of refined sugar and improperly prepared grains in the standard American diet. At least, when it comes to meat, healthy options – such as nitrite – and nitrate-free bacon and deli meats, meats cured with sea salt, and pastured meats – are becoming easier to find. Using marinades, avoiding high-heat cooking of meats, and eating plenty of vegetables and naturally fermented foods are great ways to improve our health.
Meat production and consumption involve complexities that can’t be ignored in the discussion surrounding processed meat, red meat, and cancer. The IARC itself admits that “it is not yet fully understood how cancer risk is increased by red meat or processed meat.”[3] This lack of knowledge is compounded by the fact that distinctions were not made between industrial and healthy, traditional foods. Moreover, too many important elements – from the specific types of meat consumed to the population demographics and lifestyle habits – were not addressed in the IARC statement. It is hoped more details will be forthcoming when the advisory group finally publishes its complete assessment (IARC Monograph #114). But before we abandon foods that our ancestors thrived on for millennia, we might consider the value of applying time-tested wisdom when confronting modern health issues.
About the Author
Miranda Weathers is a Florida-based multi-passionate artist, writer, and mother studying permaculture alongside nutrition and herbal medicine. She is dedicated to restoring traditional food, medicine, and lifestyle practices in communities that are affected by social structures limiting their accessibility. A curious jack of all trades, she has a hand in everything from esoteric studies to musical performance to crafting jewelry and bath products. Contact Miranda at mirandaweathers@gmail.com and see her work at mirandaweathers.com.
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- World Health Organization. International Agency for Research on Cancer. IARC Monographs evaluate consumption of red meat and processed meat. Press release no. 240. October 26, 2015.
- Bouvard V, Loomis D, Guyton KZ, et al. Carcinogenicity of consumption of red and processed meat. The Lancet Oncology. 2015; 16(16):1599-1600.
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- Gunnars K. Are nitrates and nitrites in foods harmful? Authority Nutrition. 2015. Available at: http://authoritynutrition.com/are-nitrates-and-nitrites-harmful/. Accessed February 22, 2016.
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Published in the Price-Pottenger Journal of Health & Healing
Summer 2016 | Volume 40, Number 2
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