Vraag en antwoord op de kankerverwekkendheid van de consumptie van rood vlees en bewerkt vlees
Bron-document: WHO – Q&A on the carcinogenicity of the consumption of red meat and processed meat
1. Wat beschouwt u als rood vlees?
Rood vlees verwijst naar al het spiervlees van zoogdieren zoals rund, kalf, varken, lam, schaap, paard en geit.
2. Wat beschouwt u als bewerkt vlees?
Bewerkt vlees verwijst naar vlees dat is getransformeerd door het te zouten, drogen, fermenteren, roken of door andere processen om de smaak te versterken of de houdbaarheid te vergroten. Het meeste bewerkt vlees bevat varkensvlees of rundvlees, maar bewerkt vlees kan ook ander rood vlees, gevogelte, slachtafval of nevenproducten van vlees zoals bloed bevatten.
Voorbeelden van bewerkt vlees zijn hot dogs (worstjes), ham, worst, cornedbeef, bilton of beef jerky maar ook ingeblikt vlees en op vlees gebaseerde producten en sauzen.
3. Waarom koos de IARC voor het evalueren van rood vlees en bewerkt vlees?
Een internationale advies commissie die in 2014 bijeenkwam adviseerde om de evaluatie van rood vlees en bewerkt vlees een hoge prioriteit toe te kennen binnen het IARC Monographs programma. Deze aanbeveling was gebaseerd op epidemiologische studies die suggereren dat een kleine toename van het risico op verschillende kankers gerelateerd kan zijn van een hoge consumptie van rood vlees of bewerkt vlees. Hoewel de risico’s klein zijn kunnen ze belangrijk zijn voor de volksgezondheid, omdat veel mensen over de hele wereld vlees eten en de consumptie van vlees toeneemt in laag- en midden-inkomens landen.
Hoewel sommige gezondheidsorganisaties het beperken van de inname van vlees al adviseren, zijn deze aanbevelingen meestal gericht op het verminderen van het risico van andere ziekten. Met dit in het achterhoofd, was het belangrijk voor IARC om gezaghebbend wetenschappelijke bewijs te leveren over de risico’s op kanker die samenhangen met het eten van rood vlees en verwerkt vlees.
4. Verandert het risico door de wijze van vlees bereiding?
door bereiding onder hoge temperaturen ontstaan samenstellingen die mogelijk bijdragen aan het risico op kanker, maar hun rol is nog niet volledig verklaard.
5. Wat zijn de veiligste methoden voor het bereiden van vlees (bv sauteren, koken, braden of barbecueën)?
Bereiding onder hoge temperaturen of waarbij het voedsel in direct contact komt met vlammen of een hete oppervlakte, zoals bij barbecueën of braden in een pan, produceert meer kankerverwekkende stoffen (zoals polycyclische aromatische koolwaterstoffen en heterocyclische aromatische amines). Er waren echter niet genoeg gegevens voor de IARC werkgroep om de conclusie te kunnen trekken dat de wijze van bereiding van vlees het risico op kanker beïnvloedt.
6. Is het eten van rauw vlees veiliger?
Er waren geen gegevens om deze vraag in relatie tot het risico op kanker te adresseren. Echter het risico op infectie door de consumptie van rauw vlees moet wel in gedachten worden gehouden.
7. Rood vlees is ingedeeld in groep 2A, waarschijnlijk kankerverwekkend voor mensen. Wat betekent dit precies?
Bij rood vlees is de indeling gebaseerd op beperkt bewijs uit epidemiologische studies die een positieve relatie aantonen tussen het eten van rood vlees en het ontwikkelen van darmkanker alsmede sterk mechanistisch bewijs.
Beperk bewijs houdt in dat er een positieve associatie is waargenomen tussen blootstelling aan een stof en kanker, maar dat andere verklaringen voor deze associatie (toeval, vertekening of verstoringen) niet konden worden uitgesloten.
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8. 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.
In the case of processed meat, this classification is based on sufficient evidence from epidemiological studies that eating processed meat causes colorectal cancer.
9. 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?
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.
10. What types of cancers are linked or associated with eating red meat?
The strongest, but still limited, evidence for an association with eating red meat is for colorectal cancer. There is also evidence of links with pancreatic cancer and prostate cancer.
11. What types of cancers are linked or associated with eating processed meat?
The IARC Working Group concluded that eating processed meat causes colorectal cancer. An association with stomach cancer was also seen, but the evidence is not conclusive.
12. How many cancer cases every year can be attributed to consumption of processed meat and red meat?
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.
13. Could you quantify the risk of eating red meat and processed meat?
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.
14. Is the risk higher in children, in elderly people, in women, or in men? Are some people more at risk?
The available data did not allow conclusions about whether the risks differ in different groups of people.
15. What about people who have had colon cancer? Should they stop eating red meat?
The available data did not allow conclusions about risks to people who have already had cancer.
16. Should I stop eating meat?
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.
17. 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 exists.
18. 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 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.
19. Can you compare the risk of eating red meat with the risk of eating processed meat?
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.
20. What is WHO’s health recommendation to prevent cancer risk associated with eating red meat and processed meat?
IARC 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.
21. Should we eat only poultry and fish?
The cancer risks associated with consumption of poultry and fish were not evaluated.
22. Should we be vegetarians?
Vegetarian diets and diets that include meat have different advantages and disadvantages for health. However, this evaluation did not directly compare health risks in vegetarians and people who eat meat. That type of comparison is difficult because these groups can be different in other ways besides their consumption of meat.
23. Is there a type of red meat that is safer?
A few studies have investigated the cancer risks associated with different types of red meat, such as beef and pork, and with different kinds of processed meats, like ham and hot dogs. However, there is not enough information to say whether higher or lower cancer risks are related to eating any particular type of red meat or processed meat.
24. Could the preservation method influence the risk (e.g. salting, deep-freezing, or irradiation)?
Different preservation methods could result in the formation of carcinogens (e.g. N-nitroso compounds), but whether and how much this contributes to the cancer risk is unknown.
25. How many studies were evaluated?
The IARC Working Group considered more than 800 different studies on cancer in humans (some studies provided data on both types of meat; in total more than 700 epidemiological studies provided data on red meat and more than 400 epidemiological studies provided data on processed meat).
26. How many experts were involved in the evaluation?
The IARC Working Group consisted of 22 experts from 10 countries.
27. What actions do you think governments should take based on your results?
IARC is a research organization that evaluates the evidence on the causes of cancer but does not make health recommendations as such. The IARC Monographs are, however, often used as a basis for making national and international policies, guidelines and recommendations to minimize cancer risks. Governments may decide to include this new information on the cancer hazards of processed meat in the context of other health risks and benefits in updating dietary recommendations.