Regularly drinking beverages like tea and coffee at very hot temperatures increases the risk of cancer of the food pipe or gullet, known as oesophageal cancer, UK research suggests.
Researchers say the findings, from a study of nearly a million people, make this the largest to date to establish the link.
In the study, people who had their drinks “very hot” had around a three times higher risk of the cancer than “warm” tea or coffee drinkers – although experts stress the overall chances of developing this cancer are low.
Steaming hot liquid can damage the cell lining of the food pipe on the way down to the stomach.
Scalding hot brews
The work by Oxford University, which is published in the International Journal of Cancer, defines any drink at 65 degrees Celsuis or above as “very hot” and posing a potential risk.
Consuming six or more hot drinks per day also raises the risk, according to data from 977,282 middle-aged men and women.
Although adding milk can cool drinks down slightly, a milky tea or coffee may still be far too hot, researchers say.
Tea made immediately after a kettle is fully boiled is touching boiling point, which is 100 degrees C (212 degrees F). Once poured into a cup, that lowers to around 90 or 95 degrees C.
The advice is to wait a few minutes before drinking so the beverage cools to a safer temperature.
Cancer Research UK says it’s difficult to put an exact time on how long a hot drink should be left to cool.
“But if you’re worried, we’d suggest just waiting until it’s comfortable to drink rather than drinking it while it’s still very hot,” the charity said.
Lead researcher Dr Keren Papier said research in South America – where many people drink a very hot herbal beverage called mate – had already shown a similar link between hot drinks and oesophageal cancer.
But she said: “More research is now needed to identify the exact drink temperatures linked to this increased risk.”
A separate study of 118 young adults who did multiple tastings of different black coffees found most only deemed the drinks to be too hot if the temperature was 70 degrees C or above.
According to one takeaway coffee cup manufacturer, the ideal temperature for hot coffee on the go is between 49 and 60 degrees C.
Should a barista want the coffee to stay hotter for longer – if a customer requests extra hot – it can be served at over 82 degrees C, says MTPak Coffee.
Small overall risk
The researchers suggest that around one or two in every 10 oesophageal cancers could be avoided if people stopped drinking very hot beverages.
Squamous cell oesophageal cancer is rare, affecting a few thousand people a year. In the UK, around a 1% of the popularion has a lifetime risk of being diagnosed with this type of cancer.
So even if scalding hot drinks might increase someone’s risk, the chances of them developing the cancer are still low.
And there are other factors, such as smoking, which are a bigger risk for oesophageal cancer.
Fiona Osgun from Cancer Research UK, which funded the study, stressed: “The most important ways to reduce the risk of this cancer type are not smoking and cutting down on alcohol.”
Symptoms of oesophageal cancer can include heartburn, indigestion or a pain in your throat or chest, along with weight loss.
