Biology / Cancer / Diet / Lifestyle

Meat Consumption and Cancer

carcinogenic agents

Classification of carcinogenic agents according to the IARC. Image Credit: International Agency for Research on Cancer.

By: Yameng Zhang Edited by: Thomas Luh

On October 26th 2015, the International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization, released a monograph (a report discussing a subject in detail) evaluating the carcinogenicity of red meat and processed meat consumption (whether they are directly involved in causing cancer). According to the report, “processed meat was classified as carcinogenic to humans (Group 1); red meat was classified as probably carcinogenic to humans (Group 2A).” The experts concluded that each 50 gram portion of processed meat eaten daily increased the risk of colorectal cancer by 18%.

The moment you see this report, you may feel scared, since meat consumption might take up a significant portion of your daily diet. I felt the same. However, after I closely looked into details of this research and its following reports, I closed the website, smiled and headed to Lerner Hall to grab my regular breakfast.

To better understand this “meat threat,” we need to know more about the classification used by the IARC monograph. There are four groups, but here we only talk about the two groups related to this case. Group 1 indicates “carcinogenic to humans,” which means that there is sufficient evidence to prove that this agent causes cancer in human beings. Group 2A indicates “probably carcinogenic to humans,” which means that there is only limited evidence of carcinogenicity in humans (but strong evidence in experimental animals or mechanisms in humans).

Do you think that agents classified in Group 2A are extremely dangerous, and definitely not safe to eat/touch/smell? The truth is, we need to be careful when interpreting this classification. This classification only indicates whether the agent causes cancer in human beings; in other words, it indicates whether there is a connection between the agent and cancer. Neither the intake (how often/how much you are exposed to this agent would cause cancer) nor the risk (the possibility that the cancer really happens; level of hazard) are included. I will provide you with some examples. Outdoor air pollution is in Group 1, but most people in China and India are still healthy, despite the severe air pollution. Solar radiation is in Group 1, but most human beings on earth do not have cancer due to solar radiation. Ethanol, found in alcoholic beverages, is also in Group 1, but many people casually drink. If hypothetical research found that drinking 1200 gallons of water a day was carcinogenic, then water would also be categorized into Group 1.

So, does the report seem less scary now? I will tell you something even more reassuring: of the 22 members in the IARC who voted on the final conclusions, seven either disagreed or chose to abstain. According to James Coughlin, a nutritional toxicologist and a consultant for the National Cattlemen’s Beef Association, this lack of complete agreement rarely ever happens. “The I.A.R.C. looks for consensus, and occasionally there’s one or two people who disagree. We’re calling this a majority opinion as opposed to a consensus or unanimous opinion.” Thus, though the monograph was released, it is not fully supported by every member of the team who released it. Some experts believe that there is only weak association, rather than absolute connection, between meat consumption and cancer.

When I examined the follow-up report relating to people’s reaction to this monograph, I found something interesting. According to a Forbes survey, the meat industry was not affected—sales did not go down, and there was no call from consumers to processed meat companies to raise their concerns. While “meat and cancer issues” are posted on our Facebook feeds everywhere, as if they were the most-important-thing-ever-to-happen-on-earth, most people just do not change their behaviors. They still eat what they have regularly eaten, or they just have what they like. This issue is just like the smoking issue. On every cigarette box, there is a printed notice that smoking is not good to your health, but the people smoke cigarettes anyway. Maybe with a little bit of guilt, but that’s it. Most people do not like change.

With numerous in-progress research projects today examining the “healthy life style”, how many really affect peoples’ lives? People who want to change and lead a healthy life are continuously modifying their lifestyle, but other people always stay the same. No matter what, people who care for their health will always be healthy; people who do not care will always be unhealthy. The percentage of healthy people on Earth will not be affected by those “do not eat this, do not eat that” report. A personal note here: spend more time, money and energy on medicine rather than healthy lifestyle reports.

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