Drinking very hot tea, coffee and other drinks regularly may be associated with a higher risk of oesophageal cancer, according to a large UK study led by researchers at the University of Oxford.
The study of around 977,000 middle-aged men and women found those drinking beverages at the highest temperature category had about three times the risk of developing esophageal squamous cell carcinoma compared to those who preferred warm drinks.
But the researchers emphasised that the overall risk of developing the cancer is still small.
The findings published in the International Journal of Cancer build on earlier research from countries where beverages like tea and maté are often drunk very hot.
What the study found
The researchers used data from two large UK studies: the UK Biobank and the Million Women Study. Participants were asked to report how often they consumed hot beverages and their preferred temperature.
The analysis found a greater association with esophageal squamous cell carcinoma among those who preferred hotter drinks. Those who said their drinks were “hot” had roughly 1.7 times the risk, and those who said they were “very hot” had roughly three times the risk compared to those who liked warm drinks. Having six or more hot drinks a day was also linked to increased risk.
But the study did not measure the actual temperature of each person’s drink. That means the results don’t pinpoint an exact temperature at which the increased cancer risk starts.
The 65°C level often quoted for very hot drinks comes from earlier international research. In 2016, the International Agency for Research on Cancer classified drinking beverages at temperatures above 65°C as “probably carcinogenic to humans.” The classification was based on evidence associating very hot beverages with esophageal cancer, in particular squamous cell carcinoma.
Why temperature might matter
They believe that repeated exposure to very hot liquids could damage the lining of the oesophagus and cause changes that could eventually increase the risk of cancer.
But we do not yet know the precise biological mechanism or the temperature at which the risk becomes significant.
Further research is needed to identify the temperatures most closely associated with increased risk, said Dr Keren Papier, lead author of the study from Oxford.
The results also seem to be valid for oesophageal squamous cell carcinoma (SCC) only. Adenocarcinoma – the other main type of esophageal cancer – was not as clearly linked to beverage temperature in the study.
What is the overall risk?
Although there has been a relative increase here, oesophageal SCC is still a rare disease in the UK.
Cancer Research UK currently estimates the lifetime risk of being diagnosed with esophageal SCC in the UK to be around 1%. The charity said the study adds to existing evidence that very hot drinks could increase the risk but stressed that other established risk factors are more important.
Major known risk factors for esophageal cancer are smoking and alcohol consumption.
Cancer Research UK says that if you are worried about the temperature of your drink, you should let your tea or coffee cool down until it is at a comfortable temperature to drink, rather than drinking it when it is still very hot.
The researchers say further studies are needed to ascertain the precise interplay of beverage temperature, frequency of consumption and other risk factors in the development of oesophageal cancer.
