Daijiworld Media Network - New Delhi
New Delhi, Oct 17: Drinking tea and coffee at very high temperatures may increase the risk of oesophageal cancer, according to a large study involving nearly one million participants in the UK.
The International Agency for Research on Cancer (IARC) classified beverages consumed at temperatures above 65°C as "probably carcinogenic to humans" in 2016. The classification was largely based on evidence linking the consumption of very hot mate, a traditional herbal drink popular in South America, with an increased risk of oesophageal cancer. Mate is often consumed at temperatures of around 70°C.
To investigate whether similar risks applied to tea and coffee drinkers in Western populations, researchers led by Keren Papier, a nutritional epidemiologist at the University of Oxford, analysed data from two major UK studies — the Million Women Study and UK Biobank. The research included 977,282 participants, making it one of the largest investigations into the relationship between hot beverages and oesophageal cancer.
Participants were asked to describe their preferred drinking temperature as 'very hot', 'hot' or 'warm' and report their daily tea and coffee consumption.
The findings showed that people who preferred very hot beverages had a 3.17-fold relative risk of developing oesophageal squamous cell carcinoma (SCC) compared with those who preferred warm drinks. Participants who preferred hot beverages had a 69% higher relative risk of the disease.
The study also found that people who consumed six or more hot drinks daily had a 71% higher relative risk of SCC than those who drank fewer than six, regardless of their preferred temperature.
The association was observed among both tea and coffee drinkers. Adding milk to these beverages did not significantly alter the relationship between drinking temperature and cancer risk.
Papier noted that international research had already linked the consumption of beverages such as mate at very high temperatures with an increased risk of certain types of oesophageal cancer. The latest findings provide further evidence that the temperature at which drinks are consumed may be an important factor in this risk.
Although the observational study cannot establish that very hot beverages directly cause cancer, the researchers suggested that allowing drinks to cool before consumption could help reduce the risk. Their estimates indicated that if people who usually drank very hot beverages switched to hot drinks, approximately 14% of oesophageal SCC cases could potentially be prevented, equivalent to around 440 cases annually in the UK.
However, the study had limitations. Participants reported their preferred drinking temperatures themselves, rather than having the actual temperatures of their beverages measured. Further research is needed to establish the relationship more precisely.
The biological mechanisms behind the association were not directly investigated in the study. However, the researchers referred to animal studies showing that exposure to liquids heated to around 70°C could cause tissue damage and lesions, while lower temperatures did not produce the same effects.
The findings, published in the International Journal of Cancer, suggest that repeated exposure to very hot beverages may damage the lining of the oesophagus. Researchers believe that the temperature of drinks, rather than their specific composition, may play an important role in the observed association with cancer risk.