Drinking tea or coffee at very hot temperatures can triple the risk of developing a major subtype of esophageal cancer.
Researchers at the University of Oxford found that individuals who prefer their hot beverages at the highest temperatures face a significantly elevated threat of squamous cell carcinoma.
The large scale epidemiological study analysed health data from almost one million people to track the dietary habits and cancer rates of the general public. The findings were published Tuesday in the International Journal of Cancer.
Squamous cell carcinoma is a primary form of esophageal cancer, a severe disease that affects the muscular tube carrying food from the throat to the stomach. Because the condition often has a low survival rate, identifying preventable lifestyle risks is a major priority for public health systems.
The Oxford team from the Cancer Epidemiology Unit reviewed records from 977,282 participants. During the monitoring period, doctors diagnosed 2,348 new cases of esophageal cancer among the group.
The clinical diagnoses included 1,045 cases of squamous cell carcinoma and 1,303 cases of adenocarcinoma, which is the other main subtype of the disease.
Temperature and quantity risks
The researchers found that participants who preferred drinking their beverages very hot had a risk of developing squamous cell carcinoma that was 3.17 times higher than those who chose to drink warm liquids.
The daily volume of hot drinks consumed by the participants also played a significant role in the medical findings.
People who reported drinking six or more cups of hot beverages each day showed a 71 percent increase in the risk of squamous cell carcinoma compared to those who drank fewer than six cups. The study authors noted that this volume risk remained even after they adjusted the statistical data to account for the temperature of the liquid.
The study defined a very hot drink as one served at a temperature above 65C. Freshly prepared tea and coffee can reach temperatures around 100C when boiling water is poured from a kettle, prompting the researchers to recommend waiting for the drink to cool before consuming it.
Thermal damage to tissue
The primary hypothesis for the increased cancer rate is that the severe heat causes direct thermal injury to the mucous membrane lining the esophagus.
This repeated heat damage compromises the integrity of the tissue. The researchers suggested this weakening could leave the area more vulnerable to physical, chemical or biological agents that can trigger or stimulate the development of tumors in the body.
The thermal impact specifically affects the squamous cells that form the inner protective layer of the digestive organ.
The research team estimated that 14 percent of esophageal squamous cell carcinoma cases could be avoided if people who drink very hot liquids simply let them cool to a standard hot temperature.
Based on consumption patterns in the British population, the authors calculated that this simple behavioural change would prevent approximately 440 cancer diagnoses in the United Kingdom every year.
The scientific paper was authored by researchers Keren Papier, Kezia Gaitskell, Sarah Floud and Gillian K. Reeves.
