The Science of Heat and Health
The core of the issue lies in a simple concept: thermal injury. Just as hot water can burn your skin, it can also burn the delicate lining of your oesophagus—the muscular tube that carries food and liquid from your throat to your stomach. While a single,
slightly-too-hot sip might only cause temporary discomfort, the concern among scientists is the effect of repeated, long-term exposure to scalding temperatures. This chronic irritation is what researchers have linked to more serious health problems. Symptoms of a mild thermal injury can include painful swallowing or a feeling that food is stuck in your chest.
What the Global Health Experts Say
This isn't just a hypothetical concern. In 2016, the International Agency for Research on Cancer (IARC), a part of the World Health Organization (WHO), looked into this very issue. After reviewing numerous studies, they classified drinking 'very hot' beverages—defined as those above 65°C (149°F)—as "probably carcinogenic to humans". It's crucial to note that the risk was linked to the temperature, not the beverage itself. Whether it's coffee, tea, or maté, the evidence suggests it's the intense heat that's the problem. Studies in regions where drinking extremely hot beverages is common, such as parts of Asia and South America, showed an increased risk of oesophageal cancer as the drinking temperature rose.
How Does This Damage Happen?
The primary theory is that repeatedly scalding the cells lining the oesophagus forces them into a constant state of repair. Every time these cells are damaged by heat, the body has to replace them. This rapid and continuous cell turnover increases the chance that a mistake will occur during cell replication. Over many years, such errors can lead to the development of abnormal cells, potentially leading to cancer. This type of damage is specifically linked to oesophageal squamous cell carcinoma, a type of cancer more common in regions where hot beverage consumption is a cultural norm.
Finding the Right 'Goldilocks' Temperature
So, how hot is too hot? The IARC points to 65°C (149°F) as the threshold for 'very hot'. Many cafes serve coffee at temperatures between 71°C and 85°C (160-185°F). To put this in perspective, water boils at 100°C (212°F). Research suggests an ideal drinking temperature for coffee is between 50°C and 60°C (122-140°F), a range that allows you to appreciate the flavour without the risk of scalding. There's no need to carry a thermometer. The best advice is simple: if a drink feels uncomfortably hot or you have to sip it very carefully to avoid burning your mouth, it's too hot for your oesophagus. Waiting just a few minutes can make all the difference.
Beyond the Beverage: Other Risk Factors
It is important to keep the risk in perspective. Major causes of oesophageal cancer in many countries include smoking and alcohol consumption. In fact, some evidence suggests the risk from hot beverages is most pronounced when combined with these other factors. The link is not with the occasional hot drink but with a consistent, long-term habit of drinking beverages at scalding temperatures. The key takeaway is not to give up your favourite hot drinks, but rather to adopt a small, simple change in your daily routine for the sake of your long-term health.
