Regular consumption of very hot tea or coffee may increase the risk of developing squamous cell carcinoma of the oesophagus by approximately three times, according to the Experts Club Information and Analysis Centre, based on the findings of a study by researchers at the University of Oxford published in the *International Journal of Cancer*.
The researchers analysed data from 977,282 adult residents of the UK drawn from two major studies – the Million Women Study and UK Biobank. The average follow-up period was 14.2 years in the first group and 11.1 years in the second. During this period, 2,348 cases of oesophageal cancer were identified, including 1,045 cases of squamous cell carcinoma and 1,303 cases of adenocarcinoma.
Participants self-reported their preferred temperature for drinking tea and coffee – warm, hot or very hot.
Compared with those who preferred warm drinks, people who regularly drank them ‘very hot’ had a 3.17-fold higher risk of squamous cell carcinoma of the oesophagus. For the ‘hot’ category, the risk was also elevated, albeit to a lesser extent. The researchers found no link between the temperature of the drinks and the risk of oesophageal adenocarcinoma.
The number of drinks consumed proved to be a separate factor. People who consumed six or more cups of hot tea or coffee a day had an approximately 71 per cent higher risk of squamous cell carcinoma of the oesophagus than those who drank fewer than six cups, even after taking into account the preferred temperature of the drink.
However, the study does not imply that coffee or tea themselves are carcinogens. The authors consider repeated thermal damage to the oesophageal mucosa to be the most likely mechanism.
Back in 2016, the World Health Organisation’s International Agency for Research on Cancer classified the consumption of beverages at temperatures above 65°C as ‘probably carcinogenic to humans’ – Group 2a. It is important to note that this refers specifically to high temperature, rather than the composition of the drink.
Oxford researchers note that approximately 13–17 per cent of participants in two British cohorts preferred ‘very hot’ drinks, whilst around 43–44 per cent consumed six or more hot drinks every day.
According to the authors’ calculations, around 14 per cent of squamous cell oesophageal cancer cases in the UK could potentially be prevented if people who prefer very hot drinks were to reduce the temperature to at least the ‘hot’ category.
However, the results should be interpreted with caution. The study is observational and demonstrates a statistical association rather than proving a direct cause-and-effect relationship. Furthermore, the temperature of the drinks was determined based on participants’ self-assessments rather than being measured with a thermometer.
The authors also emphasise that the absolute risk of developing the disease remains relatively low. Among nearly 1 million participants, 1,045 cases of squamous cell carcinoma of the oesophagus were recorded over more than a decade of follow-up. Therefore, a threefold increase in relative risk does not mean that one in three people who regularly drink very hot tea or coffee will develop the disease.
The most practical conclusion from the study is simple: there is no need to give up coffee or tea, but it is worth allowing the drinks to cool down a little before drinking them.
The main proven risk factors for squamous cell carcinoma of the oesophagus also include smoking and alcohol consumption. The International Agency for Research on Cancer emphasises that these remain among the main causes of the disease in many countries.