Australasian Science: Australia's authority on science since 1938

Very Hot Drinks Are a Likely Cancer Risk

The World Health Organization has found that drinking very hot drinks is a likely cancer risk but there is no evidence of a link between coffee and cancer.

The International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization, has found no conclusive evidence that coffee causes cancer. The group did however find that drinking very hot drinks (65 degrees or above) probably causes cancer of the oesophagus. This finding suggests that it is the temperature of drinks rather than the drinks themselves that is important when it comes to cancer.

IARC have classified the consumption of coffee as "not classifiable as to its carcinogenicity to humans" (Group 3). A Group 3 evaluation does not mean coffee drinking has been proved safe when it comes to cancer, but it means that there is not enough evidence to say it is hazardous. Coffee drinking was previously categorised as Group 2B or "possibly carcinogenic to humans" on the basis of a link to bladder cancer, the experts say this link has become weaker and it is no longer possible to determine if coffee causes bladder cancer.

Tea was not evaluated as part of this review.

“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.”

Professor Sanchia Aranda is CEO of Cancer Council 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."

Dr Christina Pollard is a Research Associate in the School of Public Health at Curtin University

"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 650 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."

Professor Ian Olver AM is Professor of Translational Cancer Research and Director of the Sansom Institute for Health Research at the University of South Australia

Source: AusSMC
Original study: Carcinogenicity of drinking coffee, mate, and very hot beverages, The Lancet Oncology, S1470-2045(16)30239-X]