Regularly drinking tea or coffee at extremely high temperatures may significantly increase the risk of developing oesophageal cancer, according to a major UK study involving nearly one million people.
Researchers from the University of Oxford found that people who regularly consumed beverages described as “very hot” had about three times the risk of oesophageal cancer compared with those who drank their beverages warm.
The findings, published in the International Journal of Cancer, are based on data from 977,282 middle-aged men and women, making it one of the largest studies to examine the relationship between drink temperature and the disease.
Drinks above 65°C considered very hot
The researchers classified beverages at 65°C (149°F) or above as “very hot” and potentially harmful to the oesophagus, the tube that carries food and drinks from the mouth to the stomach.
Scientists believe repeatedly exposing the lining of the oesophagus to scalding liquids could cause cellular damage and inflammation, potentially contributing to cancer development over time.
The study also found that drinking six or more hot beverages a day was associated with a higher risk.
However, experts emphasize that the overall risk remains relatively small, because oesophageal cancer is uncommon.
How hot is too hot?
A freshly boiled kettle reaches about 100°C (212°F). When the water is poured into a cup, the temperature typically falls to around 90–95°C, meaning a freshly made cup of tea or coffee can initially be considerably hotter than the level identified as potentially risky.
Adding milk can reduce the temperature, but researchers caution that a milky tea or coffee can still be dangerously hot if consumed immediately.
Cancer Research UK advises people concerned about the risk to wait until their drink is comfortable to consume, rather than drinking it while it is still steaming hot.
There is no universally recommended cooling time because the rate at which a drink cools depends on factors such as the cup, volume and surrounding temperature.
Evidence from other countries
Lead researcher Dr Keren Papier said the findings build on previous research from South America, where drinking very hot mate, a traditional herbal beverage, has also been linked to oesophageal cancer.
She said further research is needed to establish precisely what temperatures begin to significantly increase the risk.
A separate study involving 118 young adults found that most participants considered black coffee too hot to drink when its temperature reached around 70°C or higher.
For comparison, one takeaway coffee-cup manufacturer recommends serving hot coffee at approximately 49–60°C. Coffee served “extra hot” can reach temperatures above 82°C.
Overall cancer risk remains low
Despite the apparent increase in relative risk, experts stress that people should not panic about their daily cup of tea or coffee.
The researchers estimate that one or two out of every 10 oesophageal cancer cases could potentially be prevented if people stopped consuming beverages at extremely high temperatures.
Oesophageal cancer remains relatively uncommon, with the lifetime risk of developing squamous cell oesophageal cancer in the UK estimated at around 1%.
Other established risk factors are considered more important. Smoking and excessive alcohol consumption, for example, are major contributors to oesophageal cancer risk.
Cancer Research UK’s Fiona Osgun said the most important measures for reducing the risk are not smoking and cutting down on alcohol.
Warning signs to watch for
Symptoms of oesophageal cancer can include:
- Persistent heartburn or indigestion
- Difficulty or pain when swallowing
- Pain in the throat or chest
- Unexplained weight loss
- Persistent symptoms that do not improve
The presence of these symptoms does not necessarily mean cancer, but persistent or unexplained symptoms should be assessed by a healthcare professional.
The practical takeaway: You do not necessarily need to stop drinking tea or coffee. Let very hot drinks cool to a comfortable drinking temperature before consuming them, particularly if you regularly drink several cups a day.
