Consuming very hot drinks, defined as those at 65 degrees Celsius (149 degrees Fahrenheit) or above, may increase the risk of esophageal cancer, according to research published in the International Journal of Cancer. The study, which analyzed data from nearly one million middle-aged adults, suggests that the high temperatures can damage the lining of the food pipe.
Researchers from Oxford University defined any drink at 65 degrees Celsius or higher as potentially risky. The study also found that drinking six or more hot beverages per day further elevates this risk. While adding milk can slightly cool a drink, even milky tea or coffee may still be too hot, the researchers noted.
When water boils, it reaches 100 degrees Celsius (212 degrees Fahrenheit). Once poured into a cup, the temperature typically drops to around 90 to 95 degrees Celsius. The advice from the researchers is to allow beverages to cool for a few minutes before drinking to reach a safer temperature.
Cancer Research UK stated that pinpointing an exact cooling time is difficult but advised that if one is concerned, waiting until a drink is comfortable to consume is advisable. Lead researcher Dr. Keren Papier pointed to existing research from South America, where the consumption of a very hot herbal beverage called mate has shown a similar association with esophageal cancer. However, she emphasized the need for more research to determine the precise temperatures linked to this increased risk.
A separate study involving young adults found that most participants only considered coffee too hot if it exceeded 70 degrees Celsius (158 degrees Fahrenheit). Manufacturers of takeaway coffee cups suggest that the ideal temperature for hot coffee on the go is between 49 and 60 degrees Celsius (120 and 140 degrees Fahrenheit). Some establishments may serve extra hot coffee at over 82 degrees Celsius (180 degrees Fahrenheit) upon customer request.