Understanding Thermal Injury
When you sip a beverage that is excessively hot, it can cause what scientists call thermal injury to the delicate lining of your oesophagus—the tube that carries food from your throat to your stomach. This isn't a one-time catastrophe, but a series of small,
repeated injuries often referred to as micro-trauma. Each time the scalding liquid touches the oesophageal walls, it damages the surface cells. Endoscopic examinations of people with this type of injury have revealed inflammation, redness, and sometimes a distinctive “candy-cane” appearance, with alternating red and white bands of damaged tissue. In the short term, this can cause symptoms like chest pain, difficulty swallowing (odynophagia), and a burning sensation. Over time, the body is forced into a constant state of repair.
What Temperature Is 'Too Hot'?
The key question is, how hot is too hot? In 2016, the World Health Organization’s International Agency for Research on Cancer (IARC) provided a crucial benchmark. After reviewing numerous studies, they classified drinking beverages hotter than 65°C (149°F) as “probably carcinogenic to humans” (Group 2A). To put that in perspective, coffee and tea are often served in cafes at temperatures between 71°C and 85°C. Studies from regions like China, Iran, and South America, where tea or maté is traditionally consumed at around 70°C, found that the risk of oesophageal cancer increased with the drinking temperature. The consensus is that any drink that forces you to wait, sip tentatively, or feels uncomfortably hot in your mouth is likely in the danger zone for your oesophagus. A comfortable drinking temperature is typically below 60°C.
The Link Between Heat and Cancer Risk
It's important to clarify that the risk is not from the coffee or tea itself, but from the temperature. The IARC found no conclusive evidence that coffee as a drink is carcinogenic; in fact, it was reclassified to Group 3, meaning it is “not classifiable as to its carcinogenicity”. The problem is the chronic injury caused by heat. When the oesophageal lining is repeatedly damaged, the cells are forced to regenerate more frequently. This constant, rapid cell turnover increases the probability of errors during cell division, which can lead to cancerous mutations over many years. This process is believed to be the primary mechanism linking very hot drinks to oesophageal squamous cell carcinoma, a specific type of oesophageal cancer.
Contextualising Your Risk
While the link is concerning, it doesn't mean every hot drink is a major danger. The increased risk is associated with the long-term, regular consumption of very hot beverages. The majority of oesophageal cancers in high-income countries are primarily linked to major risk factors like smoking and alcohol consumption. However, in parts of the world where these cancers are prevalent without high rates of smoking and drinking, very hot beverages are considered a significant contributing factor. The risk from hot drinks can also be compounded by these other lifestyle factors. For instance, some evidence suggests that thermal injury may make the oesophagus more vulnerable to the carcinogens found in tobacco and alcohol. The takeaway is that it's a piece of a larger puzzle of lifestyle habits.
Simple Steps for Safer Sipping
The good news is that reducing this risk is simple and doesn't require giving up your favourite beverages. The solution is simply to let them cool down. Instead of sipping a steaming cup immediately, wait a few minutes. A study published in the British Medical Journal found that drinking tea less than two minutes after pouring was associated with a five-fold higher risk compared to waiting four or more minutes. You can also cool your drink down by adding milk or a splash of cool water. Be mindful of takeaway cups with lids, as they can trap heat and make it difficult to judge the temperature. The goal is to enjoy your drink when it's pleasantly warm, not scalding hot.
