Research indicates that very hot beverages, such as tea and coffee, may significantly increase the risk of developing certain cancers, particularly oesophageal cancer. According to the International Agency for Research on Cancer, drinking extremely hot drinks, specifically those served above 65°C, is classified as “probably carcinogenic to humans.” This classification aligns with other known risks, such as exposure to indoor wood smoke and the consumption of excessive red meat.
The concern arises particularly from evidence gathered over the years, much of which originates from studies in South America. These studies have documented a correlation between the consumption of maté, a traditional herbal drink typically enjoyed at around 70°C, and an increased incidence of oesophageal cancer. Similar findings have emerged from regions in the Middle East, Africa, and Asia, reinforcing the notion that very hot beverages pose a health risk.
Recent Findings in the United Kingdom
A recent, extensive study involving nearly 500,000 adults in the United Kingdom has confirmed the link between the consumption of very hot drinks and oesophageal cancer. Researchers discovered that individuals who drank eight or more cups of very hot tea or coffee daily were nearly six times more likely to develop this form of cancer compared to those who avoided hot beverages altogether. This significant finding adds to the growing body of research indicating that the temperature of drinks, rather than the type of beverage consumed, is primarily responsible for the heightened cancer risk.
The mechanism behind this risk appears to be related to the potential for hot drinks to damage the cells lining the oesophagus. Damage to these cells, if chronic, may lead to the development of cancer over time. The theory was first suggested almost 90 years ago and has been supported by various animal studies. For instance, a study conducted in 2016 highlighted that mice exposed to water at 70°C developed precancerous growths more rapidly than those given cooler water.
Understanding the Risk Factors
The extent of cancer risk may depend on not just the temperature but also the quantity of hot liquid consumed in one sitting. Research indicates that larger sips of hot drinks can create a more significant thermal injury within the oesophagus. For example, when individuals took a sip of 65°C coffee measuring 20 millilitres, temperatures inside the oesophagus could rise by as much as 12°C. This sustained heat exposure could lead to cellular damage over time.
In contrast, occasional small sips of hot beverages are unlikely to result in long-term harm. Nevertheless, consistent consumption of very hot drinks poses a genuine concern that warrants attention.
The brewing temperatures for beverages like coffee often approach the boiling point of water, with takeaway drinks sometimes served around 90°C to accommodate for cooling during transport. Research from the United States suggests that the ideal temperature for drinking coffee, which balances flavor retention and the risk of heat injury, is around 57.8°C.
To mitigate potential risks, experts advise allowing hot drinks to cool before consumption. A study showed that the temperature of a hot drink could decrease by 10–15°C within five minutes. Additionally, taking smaller sips can help test the drink’s temperature, reducing the risk of thermal injury to the oesophagus.
Vincent Ho, an Associate Professor and Clinical Academic Gastroenterologist at Western Sydney University, emphasizes the importance of these findings and encourages individuals to be mindful of their hot beverage consumption. As more research emerges, it remains crucial for consumers to be aware of the potential health implications associated with very hot drinks.
