Drinking very hot tea and coffee could triple the risk of developing oesophageal squamous cell carcinoma (SCC), a form of cancer affecting the gullet, according to the world’s largest study on the subject.
The research, which involved almost 980,000 people in the UK and followed participants over 14 years, found that both the temperature of the drink and the frequency of very hot consumption increased the likelihood of developing SCC. However, the study noted no increased risk for adenocarcinoma (AC), the other primary type of oesophageal cancer.
Published on Wednesday in the International Journal of Cancer, the study revealed that "consumption of drinks at a ‘very hot’ versus ‘warm’ temperature was associated with a threefold greater SCC risk but not with AC risk, after adjustment for consumption frequency."
Dr Keren Papier, a senior nutritional epidemiologist at the University of Oxford’s population health department, led the research. Her team further stated: "After controlling for drink temperature, daily consumption of six or more versus fewer than six hot drinks was associated with a 71% increase in SCC risk, with little association with AC risk."
The findings are based on self-reported preferences for hot drinks, with participants classifying their consumption as "very hot," "hot," "warm," or "do not drink hot drinks." The conclusions for a western European population are consistent with similar studies previously conducted in Asia, Africa, South America, and the Middle East, which linked drinking tea or mate (a caffeinated herbal drink) at or above 70C to an increased risk of oesophageal cancer.
The International Agency for Research on Cancer (IARC), a division of the World Health Organization (WHO), classified very hot drinks as “probably carcinogenic to humans” and "one probable cause of oesophageal cancer" in 2016. The heightened risk is believed to stem from heat damage to the cells lining the oesophagus, also known as the foodpipe. Other significant risk factors for this type of cancer include alcohol consumption and smoking.
The study team suggests that these latest findings could be utilised by health authorities to encourage the public to opt for cooler drinks and reduce the intake of very hot beverages, potentially leading to a decrease in SCC diagnoses. They estimated that one in seven cases of SCC in the UK "could be avoided if individuals who reported consuming their drinks at a ‘very hot’ temperature instead consumed them at a temperature more representative of the temperature range described as ‘hot’."
Researchers added: "The fact that we observed a clear trend in risk across self-reported temperature categories suggests that further limiting the temperature at which individuals consume their drinks to something well below average for this population may well avoid an even greater proportion of SCC cases." They concluded that "this large UK study of middle-aged adults, amongst whom hot drinks are widely consumed, provides clear evidence that temperature and frequency of hot drink consumption represent useful targets for SCC prevention."
Fiona Osgun, head of health information at Cancer Research UK, which funded the study, advised: "It’s difficult to put an exact time on how long a hot drink should be left to cool. But if you’re worried, we’d suggest just waiting until it’s comfortable to drink rather than drinking it while it’s still very hot." However, the charity does not currently advocate for cafes, coffee shops, and restaurants to lower their serving temperatures to mitigate SCC risk.
Professor Muy-Teck Teh, a molecular oral oncologist at Queen Mary University of London, acknowledged the research’s significance but highlighted a potential limitation. He commented that the study's reliance on self-reported temperatures could affect the findings, as perceived drink temperature is inherently subjective. He raised the possibility that "individuals who tolerate or prefer very hot drinks have altered thermosensation or mucosal sensitivity that might itself reflect underlying biological predisposition to squamous cell carcinoma and lead them to prefer hotter drinks." Professor Teh concluded that "this possibility cannot be excluded and complicates interpretation of causality."
