A recent World Health Organisaton (WHO) report has classified red meat as probably carcinogenic and processed meat as carcinogenic to humans.
The Food Safety Authority of Ireland (FSAI) has compiled a list of questions and answers so that consumers can understand better what exactly this report means:
The IARC is the International Agency for Research on Cancer and it is an agency of the World Health Organization, (WHO) that looks at substances and other environmental factors which pose a risk of cancer in humans e.g. chemicals, lifestyle factors.
They do this by asking a panel of experts to evaluate the balance of evidence in the scientific data concerning a particular environmental factor and the risk of cancer.
What is red meat?
The IARC report refers to red meat as all mammalian muscle meat, including, beef, veal, pork, lamb, mutton, horse, and goat. It does not include poultry and fish.
What is processed meat?
The IARC report refers to processed meat as meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation e.g. hot dogs (frankfurters), ham, sausages, bacon and salami.
What is a carcinogen?
A carcinogen is a substance that has been associated with cancer in humans.
What does the IARC classification system for carcinogens mean?
The IARC classifies carcinogens into five categories as follows:
It is important to understand that this classification system indicates the weight of the evidence as to whether an agent is capable of causing cancer.
It does not measure the likelihood that cancer will occur as a result of exposure (i.e. the level of risk) so it is not an indication of how potent the agent is as a carcinogen.
Red meat was classified as Group 2A "probably carcinogenic to humans". What does this mean exactly?
In the case of red meat, the classification is based on limited evidence from epidemiological studies (studies involving observations of cancer rates in different groups of people eating different diets) showing positive associations between eating red meat and developing colorectal cancer as well as strong mechanistic evidence (reasons for how red meat might cause cancer).
Processed meat was classified as Group 1, "carcinogenic to humans". What does this mean?
This category is used when there is sufficient evidence of carcinogenicity in humans. In other words, there is convincing evidence that the agent causes cancer.
The evaluation is usually based on epidemiological studies showing the development of cancer in exposed humans.
What types of cancer is linked to red meat consumption and how could it happen?
The strongest, but still limited, evidence for an association with eating red meat is for colorectal cancer. This is cancer of the colon and/or rectum which are both parts of the bowel.
There are compounds in red meat like haemoglobin that can trigger production of N-nitroso compounds during digestion and these chemicals can be carcinogenic.
Also cooking red meat at high temperature (grilling, frying, roasting, barbequing) can also lead to the formation of chemicals that can be carcinogenic e.g. polycyclic aromatic hydrocarbons.
Should I cook my red meat less?
It is important to cook red meat thoroughly to an internal temperature of at least 75 degrees Celsius to kill harmful bacteria.
The exceptions to this are whole, untenderised cuts of beef or lamb e.g. steaks, which can be cooked to preference.
However, the less browned or burned the outside of the meat is, the fewer carcinogenic chemicals are formed.
What types of cancer is linked to processed meat consumption?
The IARC concluded that eating processed meat causes colorectal cancer.
An association with stomach cancer was also seen, but the evidence is not conclusive.
The consumption of processed meat was associated with small increases in the risk of cancer in the studies reviewed.
There are similar compounds in processed meats as red meats that may cause cancer (see Q. What types of cancer is linked to red meat consumption and how could it happen?) processed meats may also contain other chemicals as a result of their processing/preservation that may be associated with cancer e.g. nitrites in cured meats.
Is there any cancer risk associated with poultry or fish intakes?
No, there is no cancer risk associated with poultry or fish intake. Poultry has much lower amounts of haemoglobin and does not trigger the production of N-nitroso compounds in the body. This may explain the lack of cancer association with poultry intake.
In many studies, fish intake appears to be protective against cancer. This may be due to some extent to the protective effects of fish oils; however some protective effects have been seen in white fish.
Should I avoid red meat altogether?
No. Lean red meat consumed in moderation can be a valuable part of a healthy diet as it is a good source of protein and a particularly good source of absorbable iron.
However, consumers should avoid consuming large quantities of red meat, especially processed meat (high in fat and salt).
What is moderation?
Healthy eating is all about ‘moderation’ which means avoiding large portion sizes and frequent consumption (i.e. be careful on how much red meat you eat at any one time and how often you eat it).
The amount of red meat you need in a day relates to your body size and an easy way to estimate this is to choose a portion that is the same size as the palm of your hand without your fingers and thumb.
On average this is approximately 100g (4oz).
Choose alternatives to meat - such as fish (protective against colon cancer), poultry (no effect on colon cancer or beans/lentils (vegetarian protein foods that provide fibre that protects against colon cancer) so that you only choose red meat as a main meal three days a week.
This keeps red meat intake to 300g per week, which is an amount previous reports have indicated is best.