Regular consumption of very hot tea or coffee can approximately triple the risk of developing squamous cell cancer of the esophagus, according to the results of a large study by Oxford University scientists published in the International Journal of Cancer.
Researchers analyzed data from 977,282 adult residents of Great Britain from two large projects — the Million Women Study and the UK Biobank. The average follow-up period was 14.2 years in the first group and 11.1 years in the second. During this time, 2,348 cases of esophageal cancer were identified, including 1,045 cases of squamous cell carcinoma and 1,303 cases of adenocarcinoma.
Participants self-reported the temperature at which they preferred to drink tea and coffee — warm, hot, or very hot.
Compared to those who preferred warm drinks, people who regularly drank them "very hot" had a lower risk of squamous cell cancer of the esophagus was 3.17 times higher. For the "hot" category, the risk was also increased, although less so. Scientists did not find a connection between the temperature of drinks and the risk of adenocarcinoma of the esophagus.
The number of drinks turned out to be a separate factor. People who drank six or more cups of hot tea or coffee per day had about a 71% higher risk of esophageal squamous cell carcinoma than those who drank less than six cups, even after taking into account the preferred temperature of the drink.
However, the study does not mean that coffee or tea itself is a carcinogen. The authors consider the most likely mechanism to be repeated thermal damage to the mucous membrane of the esophagus.
In 2016, the International Agency for Research on Cancer of the World Health Organization assigned the consumption of beverages with a temperature above 65°C to the category of "probably carcinogenic to humans" - group 2A. At the same time, it is about the high temperature, and not about the composition of the drink.
Oxford researchers note that approximately 13-17% of participants in two British cohorts preferred drinks "very hot", and about 43-44% consumed six or more hot drinks daily.
According to the calculations of the authors of the work, about 14% of cases of squamous cell cancer of the esophagus in Great Britain could potentially be prevented if people who prefer very hot drinks lowered the temperature to at least the "hot" category.
However, the results should be interpreted with caution. The study is observational and shows a statistical association rather than proving direct cause and effect. In addition, the temperature of the drinks was determined based on the participants' self-assessment, and not measured by a thermometer.
The authors also emphasize that the absolute risk of the disease remains relatively small. Among nearly 1 million participants, 1,045 cases of esophageal squamous cell cancer were recorded over more than a decade of follow-up. Therefore, a threefold increase in the relative risk does not mean that the disease will occur in every third person who regularly drinks very hot tea or coffee.
The most practical conclusion of the study is simple: it is not necessary to give up coffee or tea, but the drinks should be allowed to cool a little before drinking.
The main proven risk factors for squamous cell cancer of the esophagus also include smoking and alcohol consumption. The International Agency for Research on Cancer emphasizes that they remain one of the main causes of the disease in many countries.
