A study involving nearly a million people has revealed new evidence that drinking coffee or tea at very high temperatures may significantly increase the risk of esophageal cancer.
According to the study conducted in the United Kingdom, published on September 8 in the International Journal of Cancer, consuming these drinks while they are very hot is associated with a three-fold increased risk of esophageal cancer.
This finding is specifically associated with esophageal squamous cell carcinoma (SCC), which is the most common type of esophageal cancer worldwide.
The esophagus is a muscular tube that transports food and drink from the mouth to the stomach.
Globally, about 604,000 new cases of esophageal cancer and about 544,000 deaths were recorded in 2020, according to the International Agency for Research on Cancer (IARC), affiliated with the World Health Organization.
The agency estimates that global cases will rise by more than 50% to nearly 1 million new cases annually by 2040.
In the UK, about 9,500 new infections appear each year, according to Cancer Research UK.
However, researchers at the University of Oxford in Britain reported in this study (which is the largest of its kind) that an estimated 14% of new cases of this cancer could be avoided if individuals consumed tea and coffee at lower temperatures.
The researchers analyzed data on nearly 980,000 middle-aged adults in the UK, who were asked questions about their hot drink consumption habits, including whether they preferred their drinks “very hot,” “hot,” or “warm,” or whether they “don’t consume hot drinks” or “prefer not to answer.”
Participants were also asked how many hot drinks they consumed daily, and were given the option to choose between “less than 6 hot drinks per day” or “6 or more hot drinks per day.”
All participants came from two large study groups, the Million Women Study and the UK Biobank.
Both groups record participants' health information periodically.
A total of 2,348 cases of esophageal cancer were recorded across the study arms during a median follow-up period of 14.2 years and 11.1 years, respectively.
Just under half of the participants reported consuming six or more hot drinks per day, while about 15% said they preferred their drinks very hot, the researchers found.
The risk of developing squamous cell carcinoma of the esophagus increased with the temperature of the drink that the study participants preferred, with people who preferred their drinks hot having a risk of cancer nearly double that of those who preferred them warm.
As for those who preferred their drinks very hot, the risk of infection was more than three times greater.
The number of drinks consumed also played an important role. After adjusting for temperature-related factors, the researchers found that consuming six or more hot drinks per day, compared to consuming less than this number, was associated with a 71% increased risk of esophageal squamous cell carcinoma.
"This is the largest study of its kind to date, and it really strengthens the evidence that consumption of hot and very hot beverages may increase the risk of this type of cancer," lead author of the study and chief nutritional epidemiologist at Oxford Population Health, Keren Babier, told CNN.
It is worth noting that the International Agency for Research on Cancer classified the consumption of very hot beverages as “possibly carcinogenic to humans” in 2016.
The agency defines “very hot” drinks as those whose temperature exceeds 65 degrees Celsius.
But Babier pointed out that most previous studies were conducted in South America, Asia, and the Middle East, where the culture of hot beverage consumption is somewhat different.
For example, people in the United Kingdom often add milk to their hot drinks, but researchers found that cancer risk did not change based on whether participants added milk to their drinks or not, provided the drinks were kept hot.
The relative risk remains low
The probability of being diagnosed with esophageal cancer remains relatively low.
This cancer accounts for only 2% of cancer cases in the United Kingdom, with individuals facing a cumulative risk of approximately 1% of developing it during their lifetime, according to Cancer Research UK.
In the United States, the National Cancer Institute estimates that esophageal cancer represented only 1.1% of new cancer cases this year.
However, “for anyone who enjoys consuming hot beverages and is concerned about these results, a simple solution is to let the drink cool,” Babier said, adding that the drink can be cooled by letting it sit for a while, adding milk or cold water to it, or blowing on it.
For his part, Ian Johnson, an epithelial cell physiologist and honorary fellow at the Quadram Institute in England, told CNN in an email: “There is previous evidence indicating that hot liquids damage the cells lining the esophagus and may cause inflammation, so there is a logical explanation for these results.”
Johnson was not involved in the study.
However, the researchers were unable to determine the exact temperatures of the drinks the participants consumed, and therefore could not know whether the temperature estimates they reported actually corresponded to specific temperatures.
In this context, a professor of oral molecular oncology at Queen Mary University in the British capital, London, said in a statement issued by the Science Media Centre: “Since the beverage temperatures were based on the participants’ own estimates, and given the extent to which their sensitivity to hot drinks varies, the results should be interpreted as indicating the presence of strong associations, and not as conclusive evidence of a causal relationship.”
Babier confirmed that smoking remains the greatest risk factor for developing this type of cancer.
