Lyon, France, 26 October 2015 – The International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization, has evaluated the carcinogenicity of the consumption of red meat and processed meat.
- Processed meat was classified as carcinogenic to humans (Group 1), based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer.
- Red meat as probably carcinogenic to humans (Group 2A), based on limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect.
What the TV medias did not tell you clearly about the hazard and risk of eating red meat and processed meat:
Hazard vs Risk
IARC classifies carcinogens in five categories ranging from carcinogenic to humans (Group 1) to probably not carcinogenic to humans (Group 4).
- Group 1: The agent is carcinogenic to humans
- Group 2A: The agent is probably carcinogenic to humans (convincing evidence that the agent causes cancer in laboratory animals and some evidence that it could cause cancer in humans, but the evidence in humans is not conclusive)
- Group 2B: The agent is possibly carcinogenic to humans (convincing evidence that the agent causes cancer in experimental animals but little or no information about whether it causes cancer in humans)
- Group 3: The agent is not classified as to its carcinogenicity to humans
- Group 4: The agent is probably not carcinogenic to humans
However, the classification indicates the weight of the evidence as to whether an agent is capable of causing cancer (technically called “hazard”), but it does not measure the likelihood that cancer will occur (technically called “risk”) as a result of exposure to the agent. The IARC Monographs Programme may identify cancer hazards even when risks are very low with known patterns of use or exposure.
The Groups indicate the strength of the evidence regarding a cancer hazard and not the risk, the risk associated with two agents classified in the same Group may be very different. Comparisons within a category can be misleading:
- Exposures may vary widely. For example, there is widespread exposure to the Group 1 agent air pollution, whereas far fewer people would be exposed to certain Group 1 chemicals, such as 1,2-dichloropropane.
- The magnitude of risk associated with exposure to two agents may be very different. Active smoking carries a much higher risk of lung cancer than does air pollution, although both are categorized in Group 1.
- The number of resulting cancers can be different; for example, tobacco smoking causes some common cancers, whereas 1,2- dichloropropane causes a rare bile duct cancer. This also applies to Group 2 agents. For example, radiofrequency electromagnetic fields and the prescription drug digoxin are each classified in Group 2B.
What types of cancers are linked with eating red meat and processed meat
- Processed meat - Colorectal cancer. An association with stomach cancer was also seen, but the evidence is not conclusive. 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%. There is also not enough information to say whether higher or lower cancer risks are related to eating any particular type of processed meat or red meat.
- Red meat - Colorectal cancer. There is also evidence of links with pancreatic cancer and prostate cancer. 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. How much meat is it safe to eat? 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 exist.
- The cancer risks associated with consumption of poultry and fish were not evaluated.
What makes red meat and processed meat increase the risk of cancer
Meat consists of multiple components, such as haem 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 at high temperatures or with the food in direct contact with a flame or a hot surface, as in barbecuing or pan-frying, 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.
Ref: http://www.who.int/features/qa/cancer-red-meat/en/
