A study that followed more than 450,000 people in China for 9 years provides evidence of a relationship between drinking hot tea every day, regular drinking and smoking, and a higher risk of esophageal cancer.
The study, led by Canqing Yu, PhD, of Peking University Health Science Center in Beijing, China, was published online February 5 in the Annals of Internal Medicine.
The risk of esophageal cancer was 5 times higher in people who drank very hot tea and also drank more than 15 grams of alcohol -- a standard alcoholic drink -- every day, compared with those who drank tea less than once a week and had fewer than 15 grams of alcohol daily.
The risk for esophageal cancer was doubled in those who drank piping hot tea each day and smoked tobacco, compared with nonsmokers who drank tea only occasionally.
"Our findings show a noticeable increase in esophageal cancer risk associated with a combination of high-temperature tea drinking, excessive alcohol consumption, and tobacco smoking," Yu and colleagues write. "They suggest that abstaining from hot tea might be beneficial for preventing esophageal cancer in persons who drink alcohol excessively or smoke."
The rate of esophageal cancer is rising globally, particularly in men in less developed countries, the study says. In China, where the rate of esophageal cancer is among the highest in the world, men who drink tea often smoke and drink alcohol.
The analysis included 456,155 participants aged 30 to 79 years who did not have a history of cancer. All were enrolled between 2004 and 2008 from five urban and five rural regions of China. At the start of the study, participants reported the temperature at which they drank tea as well as some of their other behaviors, including drinking alcohol and smoking.
After 9 years, researchers found 1731 cases of esophageal cancer reported in 1,106 men and 625 women.
Although the study showed no higher odds of esophageal cancer in participants who drank only tea every day -- scalding or not -- the study authors emphasize that "chronic thermal injury to the esophageal mucosa may initiate carcinogenesis," or the change of normal cells to cancer cells.
Previous research has suggested that damage to the protective lining of the esophagus increases the risk from other things, such as excessive drinking and smoking, they note.
The International Agency for Research on Cancer recently classified drinking beverages hotter than 149 F as "probably carcinogenic to humans," the authors point out. Adding drinking and smoking to the mix "considerably complicate[s] the association between tea drinking and esophageal cancer risk."
More prospective studies that directly measure tea temperature are needed, the study authors say.
In an accompanying editorial, its authors agree that more studies are needed.
The hypothesis that drinking very hot beverages may cause esophageal cancer has been around since the 1930s, they note. "Despite this study's rigorous design and careful analysis, its results are observational and may still reflect confounding by other factors and chance," the authors write.
They say that researchers estimated tea temperature by asking people when the study first started. Until more is known, these results "should be interpreted cautiously," the editorial says.
They note that tea lovers who are concerned about cancer risk don't have to give up one of the world's most popular beverages.
"Perhaps those of us who drink hot beverages often should be prudent and wait for the liquid to cool a bit first. However, the results of this study should not cause people to abandon their favorite beverage. Most people drink their tea and coffee at a temperature that seems unlikely to cause cancer," the editorial says.
To date, studies have provided little evidence of risk to health from hot drinks consumed at temperatures less than 149 F, they say. In the United States, "coffee typically is consumed" around 140 F.
The study was supported by the National Natural Science Foundation of China, the National Key Research and Development Program of China, the Kadoorie Charitable Foundation, the Wellcome Trust (United Kingdom), and the Chinese Ministry of Science and Technology. Yu, the study co-authors, and the editorialists have disclosed no relevant financial relationships.