Very hot beverages probably carcinogenic to humans
An investigation by the World Health Organisation (WHO) and the International Agency for Research on Cancer (IRAC) has concluded drinking very hot beverages probably causes cancer of the oesophagus in humans.
The investigation did not find any conclusive evidence to say consuming coffee can cause cancer.
“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,” said Dr Christopher Wild, IARC Director.
The conclusion that very hot beverages can “probably” cause cancer was based on limited evidence linking oesophagus cancer and drinking very hot drinks. The researchers for example found in countries where tea is drunk very hot (approximately 70 degrees celsius) there was an increased risk of orsophageal cancer as the beverage temperature increased.
“Smoking and alcohol drinking are major causes of oesophageal cancer, particularly in many high-income countries,” stresses Dr Wild said.
“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.”
Australia’s experts react to investigation findings
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.”
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.”
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!”
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.”
Dr Christina Pollard is a Research Associate in the School of Public Health at Curtin University in Western Australia:
“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.”
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.”
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