The Global Scientific Consensus
In 2016, the International Agency for Research on Cancer (IARC), a part of the World Health Organization, classified drinking very hot beverages as “probably carcinogenic to humans”. This conclusion was based on multiple studies, particularly from regions
in Asia, South America, and East Africa where it is common to drink tea or other infusions at very high temperatures, often around 70°C. Researchers found that the risk of oesophageal cancer increased with the temperature of the beverage. Crucially, the IARC clarified that the risk is associated with the temperature itself, not the chemical properties of drinks like coffee or tea when consumed at normal temperatures.
How Heat Harms the Oesophagus
The primary mechanism behind the increased risk is thermal injury. Repeatedly consuming scalding liquids damages the cells lining the oesophagus, the muscular tube connecting the throat to the stomach. This repeated injury can lead to chronic inflammation. Over time, this constant state of cellular repair and turnover can increase the chances of errors in cell DNA, potentially leading to mutations that cause cancer. This specific type of cancer is known as oesophageal squamous cell carcinoma. Studies have shown that ingesting very hot liquids can cause visible, though often reversible, injury to the oesophageal mucosa, including phenomena like the 'candy-cane' esophagus seen during endoscopies.
Putting the Risk in Perspective
While the link is concerning, it's important to contextualise it. Oesophageal cancer is the eighth most common cancer worldwide. Major risk factors, especially in Western countries, include smoking and heavy alcohol consumption. The risk from hot beverages is an additional factor, and its significance can be greater when combined with other risks like smoking or drinking alcohol. However, in parts of the world where oesophageal cancer rates are high but smoking and alcohol use are less prevalent, the habit of drinking very hot beverages is a key area of study. A study in Assam, India, a region within the 'oesophageal cancer belt', found a statistically significant association between drinking very hot beverages and cancer risk.
What Temperature Is Too Hot?
The IARC defines 'very hot' as any beverage consumed at a temperature above 65°C (149°F). This is hotter than most people would find comfortably drinkable. For context, a freshly brewed coffee can be served at temperatures well above this. However, most people let their drinks cool or add milk, which lowers the temperature significantly. A recent large-scale UK study reinforced the risk, finding that individuals who described their drinks as 'very hot' had a threefold higher risk of developing oesophageal squamous cell carcinoma compared to those who drank them 'warm'. This suggests that even self-perceived temperature preference is a strong indicator of risk.
Simple Changes for Safer Sipping
The good news is that this risk is easily manageable and doesn't require giving up your favourite beverages. The most straightforward advice from health experts is to simply wait. Letting your tea or coffee cool down for a few minutes before you start sipping is the most effective step you can take. Adding milk or a splash of cool water can also rapidly lower the temperature to a safer level. A simple rule of thumb: if a drink is so hot that you have to take tiny, careful sips, it's probably too hot. Wait until you can drink it comfortably without scalding your mouth. This small change in habit allows you to continue enjoying your daily ritual without the associated thermal injury risk.
