The Link Between Heat and Health
It’s not the coffee or tea itself that poses a risk, but the temperature at which it's consumed. In 2016, the International Agency for Research on Cancer (IARC), a part of the World Health Organization, classified drinking very hot beverages above 65°C
(149°F) as "probably carcinogenic to humans". This conclusion came after reviewing numerous studies which found a consistent link between the habit of drinking scalding hot liquids and a higher incidence of a specific type of cancer: oesophageal squamous cell carcinoma (SCC). This type of cancer affects the cells lining the oesophagus, the muscular tube that carries food and liquid from your throat to your stomach.
How Does Thermal Injury Occur?
When you repeatedly drink liquids that are excessively hot, you cause recurrent, low-grade burns to the lining of your oesophagus. Think of it as a constant state of injury. Your body, in its amazing ability to heal, continuously works to repair this damaged tissue. However, this chronic cycle of injury and repair can lead to persistent inflammation. Over many years, this inflammation can increase the chances of errors occurring in the cells' DNA as they replicate, potentially leading to the formation of cancerous cells. This risk can be even more pronounced when combined with other risk factors for oesophageal cancer, such as smoking and alcohol consumption.
Defining 'Too Hot'
So, how hot is too hot? The scientific consensus points to a threshold of around 60°C to 65°C (140°F to 149°F). Studies, including a major one from the University of Oxford, have shown that people who describe their drinks as "very hot" have a significantly higher risk—up to three times greater—of developing oesophageal SCC compared to those who drink them at a "warm" temperature. To put this in perspective, a freshly brewed kettle of tea can be close to 100°C, and coffee is often served well above 70°C. The ideal drinking temperature for both safety and enjoyment is generally considered to be below 60°C.
A Global and Local Concern
This isn't a new concern and it's not limited to one part of the world. High rates of oesophageal cancer have been observed in regions across Asia, South America, and the Middle East where consuming very hot beverages is a strong cultural tradition. For instance, studies in Iran, where very hot tea is popular, and in South America with the consumption of hot maté, have long shown this association. In parts of China and even India, where dietary habits can include very hot foods and drinks, researchers have noted an increased risk. The key takeaway is that the risk is tied to a long-term habit, not the occasional cup that's a bit too hot.
Simple Changes for a Safer Sip
The good news is that reducing this risk is incredibly simple and doesn't require giving up your favourite hot drinks. The solution is simply to let them cool down. Instead of sipping immediately after pouring, wait a few minutes. A simple test is to take a small sip first; if it feels uncomfortably hot, it's best to wait. Adding a splash of cold milk or water is another easy way to bring the temperature down quickly. These small adjustments to your daily routine can significantly lower the risk of thermal injury to your oesophagus without sacrificing the comfort of your daily brew.
