Very hot drinks may be linked to a 90 per higher risk of oesophageal cancer, a study of 50,000 people suggests.
Experts found that drinking 700ml per day of tea at 60 degrees Celsius or higher was "consistently associated" with a 90 per cent increased risk of the disease, compared with people who consumed drinks at lower temperatures.
Published in the International Journal of Cancer, the study looked at the drinking habits of 50,045 people aged 40 to 75 who lived in northeastern Iran.
During a follow-up period from 2004 to 2017, 317 new cases of oesophageal cancer - also known as cancer of the food pipe - were identified.
Lead author Dr Farhad Islami, from the American Cancer Society, said: "Many people enjoy drinking tea, coffee, or other hot beverages.
"However, according to our report, drinking very hot tea can increase the risk of oesophageal cancer, and it is therefore advisable to wait until hot beverages cool down before drinking.
"As long you're letting your tea cool down a bit before you drink it, or adding cold milk, you're unlikely to be raising your cancer risk."
In 2016, the International Agency for Research on Cancer - the cancer agency of the World Health Organisation - classified drinking very hot beverages above 65C as a probable carcinogen.
The IARC examined studies that mostly looked at mate, a type of tea that is traditionally drunk at very hot temperatures, mainly in South America, Asia, and Africa.
They said it was the temperature rather than the type of drink that was associated with cancer.
The new study did not mention mate but examined tea.
The researchers behind the new study, including from the University of Cambridge, concluded: "Our results substantially strengthen the existing evidence supporting an association between hot beverage drinking and (oesophageal cancer)."
Anna Diaz Font, science program manager at World Cancer Research Fund which part-funded the study, said: "These new findings don't mean that tea lovers can't enjoy a hot drink. However, with around 500,000 new cases of oesophageal cancer worldwide each year prevention is key.
"Our research has also shown that people can reduce their risk of oesophageal cancer by being a healthy weight and cutting down on alcohol."
Professor Mel Greaves, from The Institute of Cancer Research, said: "It isn't clear why or how hot liquid has this apparent effect.
"Possibilities include direct damage to the oesophageal lining cells, another that hot liquid functions, in smokers, as a solvent for cigarette tar, washing chemical carcinogens down the oesophagus.
"As smoking is a recognised risk factor for oesophageal cancer both mechanisms could play a part, interacting to increase risk in the case of smokers who 'like it hot'."
