For many in the UK, a steaming cup of tea or coffee is a daily ritual. However, new research suggests that enjoying your beverage too hot could pose a significant health risk, specifically increasing the chance of developing oesophageal cancer.
The Scientific Link Between Heat and Cancer
In 2016, the International Agency for Research on Cancer (IARC) classified drinking very hot beverages above 65°C as "probably carcinogenic to humans". This classification places it in the same risk category as emissions from indoor wood burning or high consumption of red meat. Crucially, the agency concluded it was the temperature, not the drink itself, that was responsible.
The initial evidence came from studies in South America, linking frequent consumption of maté – a herbal drink traditionally served at around 70°C – with higher rates of oesophageal cancer. Similar patterns were observed in research from the Middle East, Africa, and Asia.
Until recently, substantial data from Western populations was lacking. This gap has now been filled by a large UK study involving almost half a million adults. The research confirmed that higher consumption of very hot tea and coffee is associated with an increased risk of oesophageal cancer.
How Much Is Too Much? Understanding the Risk
The UK study produced a striking finding. It indicated that an individual who drinks eight or more cups per day of very hot tea or coffee was almost six times more likely to develop oesophageal cancer compared to someone who does not consume hot drinks.
The mechanism behind this link is believed to be heat damage. Consuming very hot liquids can injure the cells lining the oesophagus. Over time, this repeated injury and the subsequent repair process can increase the likelihood of cancerous changes.
Animal studies support this theory. For instance, a 2016 study on mice prone to cancer found that those given very hot water (70°C) developed precancerous growths in the oesophagus sooner and more frequently than those given cooler water.
Finding the Safe Zone: Temperature and Consumption Tips
So, what is a safe temperature? While brewing often requires near-boiling water for optimal flavour, the drink should cool before consumption. A US study that balanced cancer risk with taste proposed an optimum drinking temperature of 57.8°C.
Critically, risk is influenced by both temperature and how you drink. Research measuring oesophageal temperature found that the size of the sip has a major impact. A large sip (20ml) of 65°C coffee can raise the internal temperature by up to 12°C, causing more significant heat injury than a small sip of a hotter drink.
Here are practical steps to enjoy your hot drink safely:
- Allow time to cool: A hot drink's temperature can drop by 10–15°C in just five minutes. Be patient.
- Remove the lid: On a takeaway cup, taking the lid off allows heat to escape twice as fast.
- Stir and add cooler liquid: Stirring helps distribute heat, and adding a splash of cold water or milk can lower the temperature quickly.
- Take small sips: Small sips allow you to test the temperature and minimise the volume of hot liquid hitting your oesophagus at once.
While the occasional hot sip is unlikely to cause harm, making these simple habits part of your daily routine could help mitigate long-term risk. The key message from gastroenterologists like Associate Professor Vincent Ho is to slow down and allow your drink to reach a safer, more enjoyable temperature.
