How Hot Is Too Hot? What New Research Says About Tea, Coffee and Cancer

Headlines warning that drinking hot tea or coffee could triple your risk of cancer have appeared across the UK this week, but before you abandon the kettle, there is some important context behind the research.

A major new study involving almost one million UK adults has found an association between drinking beverages at very high temperatures and an increased risk of one particular form of oesophageal cancer.

Crucially, researchers are not saying that tea or coffee itself causes cancer. The evidence suggests it is the temperature of the drink that matters. Researchers from Oxford Population Health analysed information from around 980,000 adults taking part in the UK Biobank and Million Women Study and followed their health records for more than a decade. Participants who consumed hot drinks were asked whether they generally drank them “warm”, “hot” or “very hot”.

Compared with people who preferred warm drinks, those reporting drinking them hot had nearly twice the risk of developing oesophageal squamous cell carcinoma, while people drinking them very hot had around three times the risk. That sounds alarming, but relative risk figures can make relatively uncommon diseases appear more frightening than they are.

Oesophageal squamous cell carcinoma is uncommon in the UK. Cancer Research UK estimates that the average lifetime risk of developing this particular type of oesophageal cancer is around 1%. That means even if an individual’s relative risk increases, their overall chance of developing the cancer can remain relatively low.

Researchers also found no evidence that tea or coffee themselves were responsible for the association. Instead, the findings add to a growing body of international evidence suggesting repeated exposure to very high temperatures may damage cells lining the oesophagus.

One theory is that repeated thermal injury causes inflammation and damage which, over many years, could make cancer more likely to develop. This isn’t an entirely new concern. The International Agency for Research on Cancer, part of the World Health Organization, has classified drinking beverages above 65°C as “probably carcinogenic to humans” since 2016.

Its assessment followed studies from countries including Iran, China and parts of South America where some drinks are traditionally consumed at particularly high temperatures.

The agency concluded that temperature appeared to be responsible for the association rather than the type of drink being consumed. However, 65°C should not be viewed as a precise dividing line where a drink suddenly becomes dangerous.

The researchers behind the latest UK study say the threshold used by international cancer experts is a practical classification rather than a proven biological cut-off. The new study also has limitations. Participants were asked whether they preferred their drinks warm, hot or very hot rather than researchers measuring the actual temperature of every drink they consumed.

This means scientists still cannot say precisely what temperature, frequency or duration of exposure would meaningfully increase an individual’s cancer risk. It is also an observational study. It can identify associations between behaviour and disease but cannot by itself prove that drinking a particular cup of tea caused someone’s cancer.

What the research does provide is further evidence supporting a relatively simple precaution: if your drink is extremely hot, allow it to cool before drinking it. There is no evidence from this study that people need to stop drinking tea or coffee altogether. And when it comes to reducing the risk of oesophageal squamous cell carcinoma, there are other factors which remain much more firmly established.

Smoking and alcohol are major risk factors for the disease, and Cancer Research UK says not smoking and reducing alcohol consumption remain the most important ways people can reduce their risk. So the message from the research is considerably less dramatic than some of the headlines might suggest. Your morning tea or coffee has not suddenly been declared dangerous. But if it is hot enough to burn your mouth, giving it a little longer to cool before taking that first sip is probably a sensible habit.

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