Source: Rita Jane Gabbett, MEATINGPLACE, 10/26/15
The World Health Organization’s International Agency for Research on Cancer (IARC) conclusion that processed meat is a carcinogen and red meat is a probable carcinogen comes with a boatload of qualifiers.
In a four-page Q&A document, the IARC makes multiple points that dilute the severity and the actual impact of their conclusions on human health risks.
For example:
Q: Processed meat was classified as carcinogenic to humans (Group 1). Tobacco smoking and asbestos are also both classified as carcinogenic to humans (Group 1). Does it mean that consumption of processed meat is as carcinogenic as tobacco smoking and asbestos?
IARC: No, processed meat has been classified in the same category as causes of cancer such as tobacco smoking and asbestos (IARC Group 1, carcinogenic to humans), but this does NOT mean that they are all equally dangerous. The IARC classifications describe the strength of the scientific evidence about an agent being a cause of cancer, rather than assessing the level of risk.
Q: How many cancer cases every year can be attributed to consumption of processed meat and red meat?
IARC: According to the most recent estimates by the Global Burden of Disease Project, an independent academic research organization, about 34,000 cancer deaths per year worldwide are attributable to diets high in processed meat. Eating red meat has not yet been established as a cause of cancer. However, if the reported associations were proven to be causal, the Global Burden of Disease Project has estimated that diets high in red meat could be responsible for 50,000 cancer deaths per year worldwide. These numbers contrast with about 1 million cancer deaths per year globally due to tobacco smoking, 600,000 per year due to alcohol consumption, and more than 200,000 per year due to air pollution.
Q: Could you quantify the risk of eating red meat and processed meat?
IARC: The consumption of processed meat was associated with small increases in the risk of cancer in the studies reviewed. In those studies, the risk generally increased with the amount of meat consumed. An analysis of data from 10 studies estimated that every 50-gram portion of processed meat eaten daily increases the risk of colorectal cancer by about 18%.
The cancer risk related to the consumption of red meat is more difficult to estimate because the evidence that red meat causes cancer is not as strong. However, if the association of red meat and colorectal cancer were proven to be causal, data from the same studies suggest that the risk of colorectal cancer could increase by 17% for every 100-gram portion of red meat eaten daily.
Q: Should I stop eating meat?
IARC: Eating meat has known health benefits. Many national health recommendations advise people to limit intake of processed meat and red meat, which are linked to increased risks of death from heart disease, diabetes and other illnesses.
Q. How much meat is safe to eat?
IARC: The risk increases with the amount of meat consumed, but the data available for evaluation did not permit a conclusion about whether a safe level exists.
Q: What makes red meat and processed meat increase the risk of cancer?
IARC: Meat consists of multiple components, such as heme iron. Meat can also contain chemicals that form during meat processing or cooking. For instance, carcinogenic chemicals that form during meat processing include N-nitroso compounds and polycyclic aromatic hydrocarbons.
Cooking of red meat or processed meat also produces heterocyclic aromatic amines as well as other chemicals including polycyclic aromatic hydrocarbons, which are also found in other foods and in air pollution. Some of these chemicals are known or suspected carcinogens, but despite this knowledge it is not yet fully understood how cancer risk is increased by red meat or processed meat.
Q: Can you compare the risk of eating red meat with the risk of eating processed meat?
IARC: Similar risks have been estimated for a typical portion, which is smaller on average for processed meat than for red meat. However, consumption of red meat has not been established as a cause of cancer.
Q: What is WHO’s health recommendation to prevent cancer risk associated with eating red meat and processed meat?
IARC: The IRAC is a research organization that evaluates the evidence available on the causes of cancer but does not make health recommendations as such. National governments and WHO are responsible for developing nutritional guidelines. This evaluation by IARC reinforces a 2002 recommendation from WHO that people who eat meat should moderate the consumption of processed meat to reduce the risk of colorectal cancer. Some other dietary guidelines also recommend limiting consumption of red meat or processed meat, but these are focused mainly on reducing the intake of fat and sodium, which are risk factors for cardiovascular disease and obesity. Individuals who are concerned about cancer could consider reducing their consumption of red meat or processed meat until updated guidelines related specifically to cancer have been developed.
The American Cancer Society also warns that IARC’s list of carcinogens needs to be considered in the appropriate context, saying: “The lists themselves say nothing about how likely it is that an agent will cause cancer. Carcinogens do not cause cancer at all times, under all circumstances. Some may only be carcinogenic if a person is exposed in a certain way (for example, swallowing it as opposed to touching it). Some may only cause cancer in people who have a certain genetic makeup. Some of these agents may lead to cancer after only a very small exposure, while others might require intense exposure over many years….Even if a substance or exposure is known or suspected to cause cancer, this does not necessarily mean that it can or should be avoided at all costs…. If you have questions…be sure to ask your doctor.”
Hazard vs. Risk
The IARC also made an important distinction between its “cancer hazard” evaluations compared to actual cancer risk.
The IARC evaluates cancer hazards but not the risks associated with exposure.
The distinction between hazard and risk is important. An agent is considered a cancer hazard if it is capable of causing cancer under some circumstances. Risk measures the probability that cancer will occur, taking into account the level of exposure to the agent.
The IARC may identify cancer hazards even when risks are very low with known patterns of use or exposure. The agency explained that identifying carcinogenic hazards is important because new uses or unforeseen exposures may lead to risks that are much higher than those currently seen.
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