by Aurora A. Saulo
A report in late October on the potential cancer-causing risk of red and processed meat by an arm of the World Health Organization—as well as its subsequent clarification—has continued to stoke debate and discussion since its release. We asked Aurora Saulo, PhD, a professor and extension specialist in food technology at the University of Hawaii at Manoa, for her expertise on what the report means and what we all can do about it.
On Oct. 26, 2015, the International Agency for Research on Cancer (IARC) working group of 22 experts from 10 countries released its report on red and processed meats. IARC classified red meat as “probably carcinogenic to humans” (Group 2A, based on “limited evidence”) and processed meats as “carcinogenic to humans” (Group 1, based on “sufficient evidence”). Red meat and processed meat are treated separately in IARC’s report.
Who is IARC?
IARC is a research organization that operates as part of the World Health Organization (WHO). IARC forms working groups that meet three times a year to evaluate how certain issues such as occupational chemicals, foods, or the sun impact the risk of cancer in people. They do not make health recommendations.
It is important to understand that the IARC classifications as a carcinogen are based on the strength of the scientific evidence (e.g., limited, sufficient, convincing) rather than the level of risk (e.g., low, high). Tobacco smoking and asbestos are both classified as IARC Group 1, carcinogenic to humans, based on available evidence. But the classification does not declare processed meat, tobacco smoking, and asbestos to be equally dangerous.
As for red meat, the evidence that red meat causes cancer was not found to be strong, and, therefore, eating red meat is not—at this time—established as a cause of cancer.
Red Meat vs. Processed Meat As Defined by IARC
IARC defined red meat as all types of mammalian muscle meat, such as beef, veal, pork, lamb, mutton, horse, and goat.
Processed meat has a more encompassing definition referring not only to red meat as IARC defined it, but also to other meats such as poultry, offal, or meat by-products such as blood that are transformed to improve preservation or enhance flavor through salting, curing, fermentation, cooking, smoking, or other processes. Examples of processed meat are hot dogs, ham, sausages, corned beef, beef jerky, canned meat, and meat-based preparations and sauces.
When exposed to high-temperature cooking methods such as grilling, barbecuing, or pan-frying, red meat generates certain types of carcinogenic compounds (e.g., polycyclic aromatic hydrocarbons and heterocyclic aromatic amines) that may contribute to carcinogenic risk. IARC applies an interesting differentiation of definitions because most people eat red meat as cooked or processed. Eating raw meat may result in foodborne illness.
The Basis of the IARC Findings
The IARC working group reviewed more than 800 studies, including large studies conducted over the past 20 years, with associations of consumption of red or processed meat with more than a dozen types of cancer in many countries and populations of diverse diets. The review was a response to a high-priority recommendation in 2014 to the IARC Monographs Program to evaluate the associations because of results of epidemiological studies suggesting that small increases in the risk of several cancers may be associated with high consumption of red or processed meats.
The IARC association between the meats and cancer was mainly for colorectal cancer, but associations were also seen for pancreatic cancer and prostate cancer. It is worth noting that the working group, based on the available scientific information, could not draw conclusions if risks differed in different groups of people (e.g., gender, age, susceptibility, history of cancer); if there was a safe amount of meat to consume; if people should only eat poultry, fish, and vegetables; if there was a safer type of red meat; if the type of preservation method contributed to the cancer risk; or if the way the meat was cooked affected cancer risk.
Using data from 10 studies, the working group concluded that each 50 g portion of processed meat eaten daily increases the risk of colorectal cancer by 18 percent, with the risk increasing as the amount of meat consumed increases. Because many consume processed meat, the working group saw a “global impact on cancer incidence [that] is of public health importance.”
An independent academic research organization called the Global Burden of Disease Project estimates that 34,000 cancer deaths per year worldwide are due to diets high in processed meat. Just for comparison, annual cancer deaths are estimated at about 1 million due to tobacco smoking, 600,000 due to alcohol consumption, and more than 200,000 due to air pollution.
Are These IARC Findings New?
IARC bases its conclusions on available scientific information. IARC does not make health recommendations. Many governments and health agencies worldwide, however, use IARC’s work in making national and international policies, guidelines, and recommendations.
But the latest IARC evaluation should not come as a surprise. In 2002, WHO recommended moderate consumption of processed meat to reduce the risk of colorectal cancer. At that time, other dietary guidelines also issued similar recommendations, but the intent was to reduce risks of cardiovascular disease and obesity through the reduction of fat and sodium intake. The recommendations then were not specific to reducing cancer risks.
What is new is that WHO has issued health advice that processed meats cause cancer in humans.
Before we drastically change our dietary habits based on WHO’s recommendation, remember that almost everything that we do—including eating food—has risks and benefits.
For example, humans need vitamin D for bone health, but there are not enough foods that can serve as sources of vitamin D. Sunlight synthesizes vitamin D in the skin, and this is good. But we also know that too much sunlight causes skin cancer. Thus, moderate exposure to sunlight will meet our need for vitamin D.
In another example, moderate amounts of alcohol may reduce the risk of developing and dying from heart disease, but too much alcohol leads to liver diseases. One should not indulge in sunlight and alcohol to experience their benefits. Rather, one should do so in moderation.
Likewise, the above IARC evaluations were mainly for colorectal cancer. Genetics has a lot to do with our predisposition to colorectal cancer. And even if we have a family history of occurrence, colorectal cancer is still a highly preventable disease.
Let’s start with the diet. We know that diet influences our health condition. Many consume meat as an excellent source of flavorful protein, but red meat or processed meats are not the only foods that we eat. We eat a variety of foods adding diversity and interest to our diet. We watch our caloric intake to maintain a healthy weight. And especially in the case of colorectal cancer, we eat dietary fiber that fruits and vegetables nicely supply.
We also know that lifestyle influences our health. Too little exercise increases the risk of colon cancer. Exercise enhances our strength, and that will minimize injuries. We listen to our body and take symptoms seriously. Blood, a change in stool size or color, or changes in bowel habits are serious signs that we must consult our physician. For those with family history of colorectal cancer, regular screening is routine. These are factors that make colorectal cancer preventable.
With all the news that ends with “___ foods cause cancer,” many get confused, even scared, and may result in picking and choosing to eat only those foods that are trending. The result may be dangerous and may cause nutritional imbalance. We must consult a dietitian or a physician before a drastic change in the diet or following trends. We must try to understand what the experts are saying. Their recommendations should make sense.
And finally, we should look at food as a necessary ingredient in life. Let’s learn to enjoy it again—in moderation. Now that makes sense!
Bouvard, V. Loomis, D., Guyton, K.Z., Grosse, Y., Ghissassi, F. E., Benbrahim-Tallaa, L., Guha, N., Mattock, H., Straif, K. for the IARC Monograph Working Group. October 26, 2015. IARC Monograph 114. Carcinogencicity of consumption of red and processed meat. Online news IARC Monograph 114. Lyon, France. http://www.meatpoultry.com/~/media/Files/MP/IARC-summary.ashx
International Agency for Research on Cancer. October 26, 2015. IARC Monographs evaluate consumption of red meat and processed meat. Press release No. 240. Lyon, France. http://www.iarc.fr/en/media-centre/pr/2015/pdfs/pr240_E.pdf
International Agency for Research on Cancer. October 26, 2015. Q&A on the carcinogenicity of the consumption of red meat and processed meat. Lyon, France. http://www.iarc.fr/en/media-centre/iarcnews/pdf/Monographs-Q&A_Vol114.pdf
International Food Information Council Foundation. October 27, 2015. International Agency for Research on Cancer (IARC) Publishes Report on “Carcinogenicity of consumption of red and processed meat.” An online IFIC news brief. http://www.foodinsight.org/iarc-who-red-meat-processed-cancer-health