Regularly drinking tea, coffee and other beverages at very high temperatures may increase the risk of developing oesophageal cancer, new research suggests.
A study led by researchers at the University of Oxford involving nearly one million people found that those who regularly consumed drinks classified as “very hot” had about three times the risk of developing oesophageal cancer compared with people who drank their beverages at warmer temperatures.
However, researchers stressed that the overall risk of developing the disease remains relatively low.
The findings, published in the International Journal of Cancer, add to previous research suggesting that repeated exposure to extremely hot drinks may damage the lining of the oesophagus, the tube that carries food and drinks from the mouth to the stomach.
What counts as a very hot drink?
The study classified beverages served at temperatures of 65°C or above as “very hot”.
Researchers analysed data from 977,282 middle-aged men and women and found that drinking six or more hot beverages a day was also associated with a higher risk of oesophageal cancer.
Although adding milk may reduce the temperature of tea or coffee slightly, researchers warned that the drink could still be hot enough to cause irritation or damage.
Freshly boiled water can reach about 100°C. When poured into a cup, the temperature typically falls to around 90°C to 95°C, meaning it may still be considerably hotter than the temperatures considered safer for drinking.
Health experts therefore recommend allowing hot drinks to cool for a few minutes before consuming them.
Cancer Research UK advises people who are concerned about the temperature of their drinks to wait until they are comfortable to drink rather than consuming them while they are still extremely hot.
Why could very hot drinks increase cancer risk?
Repeated exposure to scalding liquids can potentially damage the cells lining the oesophagus. Over time, repeated irritation and damage may contribute to changes that increase the risk of cancer.
Lead researcher Dr Keren Papier said previous research, particularly in South America where very hot herbal drinks such as mate are commonly consumed, had also identified a possible connection between extremely hot beverages and oesophageal cancer.
However, she said further research is needed to determine the precise temperatures at which the risk begins to increase.
A separate study involving 118 young adults found that most participants considered black coffee too hot to drink when temperatures reached about 70°C or higher.
Coffee served for takeaway consumption is generally cooler. One coffee cup manufacturer recommends temperatures between 49°C and 60°C for hot coffee consumed on the go.
Overall risk remains low
Despite the findings, experts emphasise that oesophageal cancer remains relatively uncommon.
Researchers estimate that between one and two in every 10 cases of oesophageal cancer could potentially be prevented if people avoided drinking beverages at extremely high temperatures.
In the UK, the lifetime risk of developing squamous cell oesophageal cancer is estimated at around 1% of the population.
Other established risk factors also play an important role. Smoking and excessive alcohol consumption, for example, are considered more significant contributors to oesophageal cancer risk.
Fiona Osgun of Cancer Research UK said the most important steps people can take to reduce their risk include avoiding smoking and reducing alcohol consumption.
Symptoms to watch for
Possible symptoms of oesophageal cancer include persistent heartburn or indigestion, difficulty or pain when swallowing, pain in the throat or chest and unexplained weight loss.
While the latest findings suggest that regularly consuming extremely hot drinks may increase the risk, researchers say more work is needed to establish the exact temperatures and drinking patterns associated with the greatest risk.
For tea and coffee drinkers, allowing a freshly prepared beverage to cool until it is comfortably drinkable may be a simple way to reduce repeated exposure to very high temperatures.
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