What counts as hot for some could be considered cold by others. But regardless of personal preference, it’s a good idea to avoid drinking beverages above 60 degrees Celsius, according to researchers in Iran.
A new study bolsters a link, found by earlier studies, between drinking very hot beverages and developing cancer of the oesophagus.
Researchers led by cancer specialist Farhad Islami of the Tehran University of Medical Sciences found that drinking more than 700 millilitres of tea per day — about two large cups — at temperatures above 60 degrees Celsius increases the risk of oesophageal squamous cell carcinoma by 90 per cent compared with drinking less tea and at lower temperatures.
It’s the only large-scale study of its kind in which actual drinking temperatures were measured instead of relying on participants’ error-prone self-reported temperatures, according to the authors.
The study, published in the International Journal of Cancer (IJC), gathered data on more than 50,000 men and women ages 40–75 in the north-eastern Iranian province of Golestan from 2004 to 2008.
Along with tea consumption, the data included socio-economic status, eating habits, and alcohol and tobacco use. Study participants were followed up annually for 10 years on average.
Trained staff who visited the study participants in their homes prepared two cups of tea, putting a thermometer in one.
When the temperature was 75 degrees Celsius, participants were asked to sip the tea. If it was their usual tea-drinking temperature or they usually drank hotter tea, it was recorded.
Otherwise, the procedure was repeated by letting the tea cool to 70 degrees or, if necessary, to 65 or then to 60. Participants’ usual tea-drinking temperature was recorded in each case – for some as simply “less than 60 degrees Celsius.”
From 2004 to 2017, 317 new cases of squamous cell carcinoma — along with adenocarcinoma, one of the two most common types of oesophageal cancer — were identified in the study participants.
After adjusting the data for other risk factors such as smoking and alcohol consumption, the researchers found that the shorter the duration from pouring tea to drinking it, the higher the risk of oesophageal cancer.
A possible reason for this, the researchers say, is that injury to oesophageal tissue caused by hot liquid may induce inflammatory processes that affect DNA and/or increase the formation of carcinogenic compounds.
The France-based International Agency for Research on Cancer (IARC) classifies “drinking very hot beverages at above 65 degrees Celsius” as “probably carcinogenic.” And the Cancer Information Service of the German Cancer Research Centre (DKFZ) warns on its website of a link between very hot drinks and oesophageal cancer. – dpa
