Before you grab your favourite hot tea or coffee, think about how hot you are drinking it. A new University of Oxford study involving nearly 1 million UK adults found that people who preferred their tea or coffee very hot had about three times the risk of oesophageal squamous cell carcinoma (SCC) compared with those who preferred their drinks warm. The study also found that drinking six or more hot drinks a day was associated with a 71% higher risk of oesophageal SCC, after accounting for drink temperature.

The study, published in the International Journal of Cancer, analysed data from over 9.77 lakh participants from two large UK cohorts, the Million Women Study and UK Biobank. During follow-up, researchers identified 2,348 cases of oesophageal cancer, including 1,045 cases of squamous cell carcinoma and 1,303 cases of adenocarcinoma.

It is important to note that the study does not show that tea or coffee themselves cause oesophageal cancer. Instead, the higher risk was linked to preferred drink temperature, suggesting that repeated exposure to very hot beverages may be an important factor.

Very hot drinks linked to oesophageal squamous cell carcinoma

Researchers combined data from the Million Women Study and UK Biobank. The Million Women Study contributed 510,112 participants, while 467,170 participants came from UK Biobank. Participants were asked how they preferred to drink hot beverages, with options including warm, hot and very hot. They were also asked about the number of cups of tea and coffee they consumed each day.

The researchers then examined whether these preferences were associated with two major types of oesophageal cancer: squamous cell carcinoma and adenocarcinoma. Participants were followed through routinely collected health records for cancer diagnoses and deaths.

During an average follow-up of 14.2 years in the Million Women Study, researchers recorded 799 cases of oesophageal SCC and 617 cases of adenocarcinoma. In UK Biobank, which had an average follow-up of 11.1 years, there were 246 SCC cases and 686 adenocarcinoma cases.

The link between drink temperature and SCC was particularly clear. Compared with people who preferred warm drinks, those who preferred hot drinks had about 80% higher risk, while those who preferred very hot drinks had about three-and-a-half times the risk. 

After additionally accounting for how many hot drinks participants consumed, the association remained strong. People who preferred very hot drinks had a 3.17-fold higher risk of oesophageal SCC compared with those who preferred warm drinks. The researchers found no material association between preferred drink temperature and oesophageal adenocarcinoma, with a relative risk of 0.92 for very hot versus warm drinks.

The researchers wrote that their findings provide evidence that “drink temperature as well as frequency” may be important risk factors for oesophageal SCC.

The distinction between the two cancer types is important. Oesophageal SCC develops from squamous cells lining the oesophagus, while adenocarcinoma has different biological and risk-factor patterns. The study’s finding that the temperature association was confined to SCC is consistent with the possibility that repeated thermal injury to the oesophageal lining may play a role.

Frequency also matters 

The researchers also looked at the frequency of hot drink consumption. Participants were grouped according to whether they consumed fewer than six hot drinks a day or six or more.

After controlling for drink temperature, consuming six or more hot drinks per day was associated with a 71% higher risk of oesophageal SCC compared with consuming fewer than six. For adenocarcinoma, the corresponding association was much smaller, with a relative risk of 1.19.

Importantly, the study did not find evidence that the effect of the number of drinks differed substantially according to the temperature category. In other words, both higher temperature and greater frequency were independently associated with SCC risk.

The researchers also carried out several analyses to test whether the findings could be explained by other factors. Adjusting for potential confounders did not materially change the association between drink temperature and SCC. The association also remained when researchers excluded cancers diagnosed during the first five years of follow-up, reducing concerns that early symptoms of undiagnosed cancer may have influenced participants’ drinking behaviour.

The researchers additionally examined whether adding milk to tea or coffee altered the association. Among participants in the Million Women Study who provided information about milk consumption, there was little evidence that adding milk changed the temperature-related risk.

This is relevant because milk could potentially alter the temperature at which a beverage is consumed. However, the researchers found similar associations among people who did and did not add milk to their drinks, further supporting the possibility that temperature itself was an important factor.

The researchers said the findings were consistent with a mechanism involving thermal injury to the oesophageal lining. Repeated exposure to very hot liquids may damage the mucosal surface and potentially contribute to processes involved in cancer development.

However, the researchers did not establish a specific temperature at which cancer risk begins. Participants were asked about their preferred temperature rather than having the actual temperature of their drinks measured. The authors noted that perceptions of what constitutes “warm”, “hot” or “very hot” can differ between people and populations.

This is particularly important when interpreting the findings alongside previous research. The International Agency for Research on Cancer has classified beverages consumed at temperatures above 65°C as probably carcinogenic to humans, based on limited evidence for oesophageal cancer. However, the Oxford researchers noted that 65°C is a classification threshold rather than a proven biological cut-off.

Previous research from countries including Iran, China and Japan has also reported associations between very hot beverage consumption and oesophageal cancer. The new study adds evidence from a large Western population, where tea and coffee are commonly consumed at temperatures generally lower than the approximately 70°C temperatures reported in some earlier studies.

The researchers estimated that, assuming the relationship is causal, about 14% of oesophageal SCC cases in the UK could potentially be prevented if people who currently drink their beverages very hot instead consumed them at temperatures categorised as hot. This was estimated to correspond to approximately 440 cases a year in the UK.

The authors also stressed that their results do not establish that every hot cup of tea or coffee is dangerous. Rather, the findings suggest that “reducing drink temperature in populations where tea and coffee are frequently consumed could offer an important means of SCC prevention.”

The scale of oesophageal cancer 

According to the World Cancer Research Fund, there were over 5.11 lakh new cases of oesophageal cancer worldwide in 2022. India recorded 70,637 new cases, making it the country with the second-highest number of cases globally that year. India’s age-standardised incidence rate was 5.0 per 100,000 people.

Oesophageal cancer also remains a major cause of cancer mortality in India. The World Cancer Research Fund reports that 66,410 people in India died from oesophageal cancer in 2022, the second-highest number of deaths recorded globally that year. The global total was over 4.45 lakh 445,391 deaths.

What doctors say

Dr Vaishnavi Joshi, Consultant, Medical Oncology & Haemato-Oncology, Aster CMI Hospital, Bengaluru, said repeatedly consuming very hot beverages could expose the oesophageal lining to thermal injury. While the oesophageal mucosa can tolerate food and liquids, repeated exposure to extremely high temperatures may cause irritation, microscopic injury and inflammation. Over time, repeated injury and tissue repair could potentially increase cellular stress and contribute to abnormal changes in the cells lining the oesophagus.

“This is biologically plausible for squamous cell carcinoma, which arises from the squamous cells lining the oesophagus,” Joshi said. She noted that the new study is particularly relevant because it found a substantially higher risk of oesophageal SCC among people who preferred very hot drinks, while no meaningful association was observed with adenocarcinoma. However, she stressed that “the findings are observational and do not by themselves establish that very hot beverages cause cancer.”

From a practical perspective, Joshi advised people to avoid drinking beverages when they are hot enough to cause discomfort or a burning sensation. “There is no universally established temperature at which an individual can say the drink becomes completely safe or unsafe,” she said.

The International Agency for Research on Cancer has classified beverages consumed above 65°C as “probably carcinogenic,” but Joshi pointed out that this should not be interpreted as a precise temperature at which cancer risk suddenly begins. “Rather than measuring every cup of tea or coffee, people should allow freshly prepared beverages to cool to a comfortably warm temperature before drinking,” she advised.

For people in India, where tea and coffee are commonly consumed, Joshi said the practical takeaway is to avoid routinely consuming beverages while they are extremely hot. “The concern is not the tea or coffee itself, but repeated exposure to very high temperatures,” she said.

She also emphasised that avoiding very hot beverages should be viewed as one part of cancer prevention, rather than a replacement for addressing established risk factors such as tobacco and excessive alcohol consumption. 

“People experiencing persistent symptoms such as difficulty swallowing, painful swallowing, unexplained weight loss or persistent chest discomfort should seek medical evaluation rather than attributing them solely to dietary habits,” she cautioned. 

Dr Amit Chakraborty, Head and Neck Cancer Surgeon, SSO Cancer Hospital, Mumbai, also highlighted the cultural preference for very hot tea in India. “Indians believe in the concept of ‘garmagaram chai’. Having hot tea is often seen as refreshing, and many people enjoy their tea piping hot,” he said.

However, he cautioned that beverages consumed at scalding temperatures can irritate and potentially damage the oesophageal lining. “Allow hot beverages to cool to a comfortable, warm temperature before drinking. Oesophageal cancer is a major health concern in India, but not everyone who drinks hot beverages will develop oesophageal cancer,” Chakraborty said.

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