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How Hot Is Too Hot? What a Study of Nearly One Million Adults Means for Tea Drinkers

By the Green Leaves, Liquid Gold tasting table · October 2026

Tea is not the suspect. Temperature is. A study published in September 2026 in the International Journal of Cancer followed nearly one million UK adults and found that people who habitually drink their tea and coffee “very hot” had about three times the risk of one type of oesophageal cancer as people who drink theirs warm. The fix costs nothing and takes a few minutes: let the cup cool. Here is what the researchers actually measured, where the limits of the study sit, and how to keep brewing hot while drinking cooler.

The study, in plain terms

Researchers at Oxford Population Health’s Cancer Epidemiology Unit, funded by Cancer Research UK, combined two large British cohorts — UK Biobank and the Million Women Study — covering 977,282 adults. Participants reported how they usually take their tea and coffee: “very hot,” “hot,” or “warm,” and how many cups they drink a day. The team then followed their health records for an average of 11 to 14 years, depending on the cohort. Oxford describes it as the largest study of its kind, and the first to test the question properly in a Western population, where earlier evidence came mostly from regions that traditionally drink maté, tea, or coffee at near-boiling temperatures.

Over the follow-up, 2,348 oesophageal cancers were recorded: 1,045 squamous cell carcinomas (SCC) and 1,303 adenocarcinomas. The temperature signal appeared only in the first type — the cancer that starts in the flat cells lining the food pipe.

The numbers that matter

• “Very hot” vs “warm”: relative risk 3.17 (95% CI 2.49–4.03) for oesophageal SCC, after adjusting for how much people drank.
• “Hot” vs “warm”: relative risk 1.69 (95% CI 1.36–2.11) — a gradient, not a cliff edge. The hotter the habit, the higher the risk.
• Six or more hot drinks a day vs fewer than six: relative risk 1.71 (95% CI 1.51–1.94) for SCC, after controlling for preferred temperature. Frequency stacks on top of heat.
• No material association with adenocarcinoma — the other main type of oesophageal cancer, which is linked mainly to chronic acid reflux and body weight.
• Tea and coffee behaved the same way, which is the point: the exposure is the heat, not the drink.
• The authors’ prevention estimate: if people who prefer “very hot” drinks switched to “hot,” roughly 14% of UK oesophageal SCC cases — about 440 a year — could be avoided.

About 15% of participants said they prefer their drinks very hot, and just under half drank six or more hot drinks a day. This is not a study of exotic behaviour. It is a study of the normal British tea round, repeated for decades.

Context before anyone worries

Honest note: this is an observational study, and participants described their preference — nobody measured the temperature in their cups. “Very hot” in one kitchen is “hot” in another. The study also cannot prove by itself that heat causes the cancer, although the proposed mechanism is straightforward: repeated scalding injures the oesophageal lining, and tissue that is constantly repairing itself is tissue where errors can accumulate.

Absolute risk matters too. Cancer Research UK puts the UK lifetime risk of oesophageal SCC at around 1%, so even a tripled relative risk leaves any individual drinker’s risk low. And as Fiona Osgun, Cancer Research UK’s head of health information, put it in response to the study, the most important ways to reduce risk of this cancer remain not smoking and cutting down on alcohol. Temperature is a smaller lever — but unlike most levers, it is free, instant, and asks you to give up nothing.

The 65-degree line is older than this study

None of this appeared from nowhere. In 2016, the World Health Organization’s International Agency for Research on Cancer (IARC) classified drinking very hot beverages — above 65°C (149°F) — as Group 2A, “probably carcinogenic to humans.” Notably, IARC pointed at the temperature, not at tea or coffee themselves. Earlier prospective research in Iran, where tea temperature was actually measured in the cup, likewise found risk rising once drinks were regularly consumed at around 60°C and above. The Oxford authors estimate that tea and coffee in Western countries are typically drunk at around 60°C — close enough to the line that the last few degrees, and the first few minutes, are worth paying attention to.

Brew hot, drink cooler: two different decisions

Here is the part tea lovers should hear clearly: brewing temperature and drinking temperature are separate choices, and good tea already separates them. Extraction needs heat — a high-mountain oolong gives up its aromatics to near-boiling water, and a pu-erh rinse is done with a rolling boil. Nothing in this research asks you to brew cooler. It asks you not to swallow the result while it is still scalding.

Traditional practice, it turns out, was built for this. Gongfu brewing pours small amounts into a fairness pitcher and then into small cups, and small volumes lose heat fast — by the time a thimble-sized cup reaches your lips, it is usually well below the temperature in the pot. Matcha is whisked with water at roughly 80°C, not boiling, and drunk in small sips from a wide bowl with a large cooling surface. The old formats were designed for flavour. They happen to handle temperature well too.

A practical routine, no equipment required:

• Pour, then wait. A mug of freshly boiled tea typically needs several minutes — often around ten, varying with the cup and the volume — to fall toward 60°C. Use the steeping time as part of the wait, then give it a few minutes more.
• Use the comfort test. Cancer Research UK’s guidance is simple: the drink should feel comfortable, not burn your tongue or lips. If the first sip makes you pull back, it is too hot.
• Decant. Pouring into a second vessel or a wide cup increases surface area and speeds cooling — the same reason a fairness pitcher works.
• Sip, don’t gulp. Small sips cool in the mouth before they go down.
• Watch the daily count. The study’s frequency signal was at six or more hot drinks a day. If that is you, the cooling habit matters more, not less.
• Want precision? A kitchen thermometer settles it: drink below 60–65°C and you are under the IARC line.

There is a flavour dividend, too. A scalding cup numbs the tongue; as tea cools toward comfortable drinking temperature, sweetness and aroma are simply easier to perceive. Waiting is not a sacrifice made for safety. For most teas, it is when the drinking actually gets good.

The short summary

A September 2026 International Journal of Cancer study from Oxford Population Health pooled 977,282 UK adults and found that drinking beverages “very hot” rather than warm was associated with a relative risk of 3.17 for oesophageal squamous cell carcinoma, with “hot” at 1.69 and six or more hot drinks a day adding further risk — while adenocarcinoma showed no material link and tea and coffee behaved identically. The result extends IARC’s 2016 classification of drinks above 65°C, and the absolute risk remains low (about 1% lifetime in the UK), well behind smoking and alcohol as risk factors. The response is a habit, not a purchase: brew as hot as your tea demands, then let the cup cool to comfortable before you drink.

The single most important point: the risk follows the temperature, not the tea — so you never have to choose between your tea and this evidence. Keep the boil in the kettle, lose it in the cup, and the habit the study flags is gone.