EXPERT REACTION: Are coffee and very hot drinks causing cancer?

Embargoed until: Publicly released:

The International Agency for Research on Cancer (IARC), the specialized cancer agency of the World Health Organization (WHO), is holding a virtual press conference to announce the results of the Monographs evaluation on Coffee, Maté and Very Hot Beverages. After a thorough evaluation of all relevant and publicly available scientific literature, a group of 23 leading international experts convened by IARC have classified the carcinogenicity of coffee, maté and very hot beverages. An Expert from the IARC Monographs Programme will present the classification results and answer questions from the media.

Journal/conference: World Health Organization

Organisation/s: The International Agency for Research on Cancer

Press Call

From: The International Agency for Research on Cancer

IARC Monographs evaluate drinking coffee, maté, and very hot beverages

Lyon, France, 15 June 2016 – An international Working Group of 23 scientists convened by the International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization (WHO), has evaluated the carcinogenicity of drinking coffee, maté,[1] and very hot beverages.

A summary of the final evaluations is published today in The Lancet Oncology,and the detailed assessments will be published as Volume 116 of the IARC Monographs.

The Working Group found no conclusive evidence for a carcinogenic effect of drinking coffee. However, the experts did find that drinking very hot[2] beverages probably causes cancer of the oesophagus in humans. No conclusive evidence was found for drinking maté at temperatures that are not very hot.

“These results suggest that drinking very hot beverages is one probable cause of oesophageal cancer and that it is the temperature, rather than the drinks themselves, that appears to be responsible,” says Dr Christopher Wild, IARC Director.

Very hot beverages

Drinking very hot beverages was classified as probably carcinogenic to humans (Group 2A).

This was based on limited evidence from epidemiological studies that showed positive associations between cancer of the oesophagus and drinking very hot beverages. Studies in places such as China, the Islamic Republic of Iran, Turkey, and South America, where tea or maté is traditionally drunk very hot (at about 70 °C), found that the risk of oesophageal cancer increased with the temperature at which the beverage was drunk.

In experiments involving animals, there was also limited evidence for the carcinogenicity of very hot water.

“Smoking and alcohol drinking are major causes of oesophageal cancer, particularly in many high-income countries,” stresses Dr Wild. “However, the majority of oesophageal cancers occur in parts of Asia, South America, and East Africa, where regularly drinking very hot beverages is common and where the reasons for the high incidence of this cancer are not as well understood.”

Oesophageal cancer is the eighth most common cause of cancer worldwide and one of the main causes of cancer death, with approximately 400 000 deaths recorded in 2012 (5% of all cancer deaths). The proportion of oesophageal cancer cases that may be linked to drinking very hot beverages is not known.

Maté

Cold maté did not have carcinogenic effects in experiments on animals or in epidemiological studies.

Therefore, drinking maté at temperatures that are not very hot was not classifiable as to its carcinogenicity to humans (Group 3).

This was based on inadequate evidence in humans for the carcinogenicity of drinking cold or warm maté and inadequate evidence in experimental animals for the carcinogenicity of cold maté as a drinking liquid.

Coffee

Drinking coffee was not classifiable as to its carcinogenicity to humans (Group 3).

The large body of evidence currently available led to the re-evaluation of the carcinogenicity of coffee drinking, previously classified as possibly carcinogenic to humans (Group 2B) by IARC in 1991.

After thoroughly reviewing more than 1000 studies in humans and animals, the Working Group found that there was inadequate evidence for the carcinogenicity of coffee drinking overall.

Many epidemiological studies showed that coffee drinking had no carcinogenic effects for cancers of the pancreas, female breast, and prostate, and reduced risks were seen for cancers of the liver and uterine endometrium.

For more than 20 other cancers, the evidence was inconclusive.

Note to the Editor:

The IARC Monographs Programme seeks to classify cancer hazards, meaning the potential of any substance to cause cancer based on current knowledge. The classification does not indicate what level of risk exists to people’s health associated with exposure to a classified hazard. For example, IARC has classified tobacco smoking as carcinogenic to humans (Group 1), but that classification does not indicate the increase in risk for each cigarette smoked.

This Working Group evaluation is in line with the WHO Technical Report Series 916 on Diet, Nutrition and the Prevention of Chronic Diseases, which states that people should not consume drinks when they are at a very hot (scalding hot) temperature.

For more information on the IARC classification, read the IARC Monographs Q&A:

http://www.iarc.fr/en/media-centre/iarcnews/pdf/Monographs-Q&A.pdf

Read the IARC Monographs Q&A on the evaluation of drinking coffee, maté, and very hot beverages:

http://www.iarc.fr/en/media-centre/iarcnews/pdf/Monographs-Q&A_Vol116.pdf

For more information, please contact

Véronique Terrasse, Communications Group, at +33 (0)4 72 73 83 66 or terrassev@iarc.fr

or IARC Communications, at com@iarc.fr.

The International Agency for Research on Cancer (IARC) is part of the World Health Organization. Its mission is to coordinate and conduct research on the causes of human cancer and the mechanisms of carcinogenesis, and to develop scientific strategies for cancer control. The Agency is involved in both epidemiological and laboratory research and disseminates scientific information through publications, meetings, courses, and fellowships. If you wish your name to be removed from our press release emailing list, please write to com@iarc.fr.


[1] Maté is an infusion made from dried leaves of Ilex paraguariensis. It is consumed mainly in South America and to a lesser extent in the Middle East, Europe, and North America. Maté is traditionally drunk very hot (at about 70 °C), but it may also be consumed warm or cold.

[2] “Very hot” refers to any beverages consumed at a temperature above 65 °C. See the Q&A for more details.

Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives and reflect independent opinion on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Emeritus Professor Mark Wahlqvist is former Professor and Head of Medicine at Prince Henry’s Hospital and Monash Medical Centre, Associate Dean (International Health and Development) and Director of the Asia Pacific Health and Nutrition Centre

As one of a diversity of hot beverages, coffee is increasingly recognised as a safe alternative to tea, water and milk, while minimising the use of sugary drinks and alcoholic beverages. This is about health in general and not just cancer. At the same time, an emphasis on beverage variety is important for biodiversity and environmental protection. Avoidance of piping hot coffee from plastic cups with the lid remains particularly important because of the increased exposure to plastic residues known to be endocrine (hormone) disruptors.

Last updated: 03 Nov 2016 7:15pm

Professor Bruce Armstrong is a Consultant in Environmental Epidemiology, Environmental Health and Health Services, an Adjunct Professor in the School of Population Health at the University of Western Australia and an Emeritus Professor in the School of Public Health at the University of Sydney

IARC reviewed more than 1,000 human epidemiological studies and animal experimental studies that investigated whether or not coffee causes cancer. Notwithstanding the large volume of research, IARC concluded that coffee drinking is unclassifiable as to its carcinogenicity (capacity to cause cancer) to humans. IARC’s report, however, found evidence that suggests that coffee drinking protects against human endometrial cancer (cancer of the lining of the uterus), liver cancer and breast cancer. This evidence was apparently not considered strong enough to suggest that coffee drinking lacks carcinogenicity (a conclusion that IARC sometimes reaches). From a practical public health perspective, however, it would be reasonable to conclude from the IARC review that coffee drinking is unlikely to increase a coffee drinker’s risk of cancer.

IARC reviewed a much smaller body of evidence on whether or not drinking very hot beverages can cause cancer of the oesophagus (gullet). It concluded from this evidence that drinking very hot beverages at above 65 degrees Celsius is probably carcinogenic to humans.

So the take-home message is: Enjoy your coffee with peace of mind but don’t drink it very hot!

Last updated: 03 Nov 2016 6:23pm
Ian Olver is Professor of Translational Heath Research and Director of the Sansom Institute for Health Research at the University of South Australia.

The International Agency for Research on Cancer scans the world literature to determine how likely it is that an agent causes cancer. In this case after reviewing 1000 animal and human studies they have found no evidence that drinking coffee causes cancers of the breast, pancreas and prostate and found reduced risk of liver and endometrial cancer.

This is a very large number of studies which gives confidence in this result. There is no evidence that any particular type of coffee is worse than any other. Coffee had previously been thought to be possibly associated with bladder cancer. This shows how just having a small number of studies can cause uncertain results which are clarified by considering a very large number of studies. It also shows that if other known causal factors are not controlled for, in this case smoking, the cause of the cancer can be attributed to an agent that is merely associated with the cancer but does not cause it.

The current IARC report makes this point in relation to very hot drinks (over 65.0 C) which have been found to probably cause cancer of the oesophagus, where it is the temperature of the drink, not the type of drink that is the factor causing the cancer.

Last updated: 03 Nov 2016 5:40pm
Professor Sanchia Aranda, CEO, Cancer Council Australia

Coffee drinkers should be comforted to know they are not increasing their cancer risk – as long as their coffee isn’t too hot. The risk applies to beverages at 65 degrees Celsius or hotter. As a guide, a beverage at that temperature is likely to be uncomfortably hot for some people to drink. So let the drink cool a little and enjoy it.

This IARC analysis should help dispel the myth that everything causes cancer – and help get the focus back on things we can all do to reduce Australia’s cancer burden.

People worry too much about exposure to things that pose no cancer risk. Right now we’ve got good evidence on how the next Australian government could save tens of thousands of lives by investing more in bowel cancer screening and anti-smoking and skin cancer awareness programs – that’s where Cancer Council Australia would like the focus to be.

Last updated: 03 Nov 2016 4:19pm
Dr Darren Saunders is a cancer biologist and senior lecturer in pathology at the University of New South Wales

This is another example that highlights the difficulties faced in weighing evidence for cancer risk from food. While lots of studies claim a link between various foods and either increased cancer risk, or a protective effect, in many cases the evidence is unconvincing and often contradictory. This can lead to general confusion among consumers, where every new study seems to contradict the previous one.
 
The IARC classifies potential carcinogens on a scale of decreasing certainty. In other words, the WHO/IARC categories refer to level of evidence, not level of risk. This is an important distinction but one that many find difficult to interpret, and the distinction is often lost or confused in media reporting. While the IARC now classify hot drinks as a probable (Group 2A) carcinogen in oesophageal cancer, we shouldn’t forget that smoking and alcohol consumption are established major risk factors.

Last updated: 03 Nov 2016 4:16pm
Dr Christina Pollard is a Research Associate in the School of Public Health at Curtin University

The cancer causing potential of drinking coffee has been re-evaluated by the International Agency for Research on Cancer (IARC) after a 25 years and has been down-graded to ‘no conclusive evidence’ as carcinogenic to humans.  The available evidence has grown substantially over the time and enabled a more extensive analysis with a variety of cancers studied. The IARC committee suggest that other factors such as smoking may have accounted for the original classification as possible carcinogenic in 1991.  At that time it was common for people to both drink coffee and smoke. 

 
Coffee consumption varies by country in type and amount.  Australia has seen an increase in consumption over the last decade and it is important to continue to monitor foods or beverages that are commonly consumed in large amounts. Australians drink more coffee than tea, the 2011-2012 Australian Nutrition Survey shows that coffee was consumed by nearly half of the population with an average intake of 300 mls (equivalent to a large mug, but most were from instant coffee powder.

(Australian Health Survey http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/by%20Subject/4364.0.55.007~2011-12~Main%20Features~Non-alcoholic%20beverages~701)

Last updated: 03 Nov 2016 4:02pm

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