DEAR DOCTOR: I'm a tea drinker, and I like it best when it's steaming hot. My sister says drinking liquids that hot is bad for you, and that they can cause cancer. Is she right? Should I be worried?
DEAR READER: About three years ago, a report that classified drinking very hot liquids as a probable carcinogen made headlines around the world. The warning came from the International Agency for Research on Cancer, an arm of the World Health Organization. The finding arose from several observational studies that linked drinking very hot liquids to an increased risk of cancer of the esophagus.
The most common hot beverage in those studies was mate, a tea widely consumed in South America, Africa and Asia. Mate is traditionally served quite hot, about 149 degrees Fahrenheit, which is scalding. Drinking the same liquids in the studies at cooler or cold temperatures was not associated with elevated cancer risk.
The report received some pushback, which included the criticism that the studies it cited did not include precise temperature data of the drinks consumed by the participants.
Since then, findings from two newer studies have made similar connections between very hot beverages and esophageal cancer. In a report published last year in the Annals of Internal Medicine, the increase in cancer risk was seen mostly in drinkers of very hot tea who also smoked or drank alcohol.
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The study analyzed the tea consumption habits of 450,000 Chinese adults over the course of almost 10 years. When consumption of very hot tea was combined with smoking and drinking, cancer risk was 2 to 5 times greater. The alcohol use associated with the increased risk was one beer, glass of wine or shot of hard liquor per day. Smoking was defined as one or more cigarettes per day.
Another study of 50,000 adults in Iran, published in the International Journal of Cancer in March, found that drinking two large cups of tea per day hotter than 140 degrees Fahrenheit resulted in almost double the cancer risk.
Cancer of the esophagus, which is the eighth most common cancer worldwide, is responsible for 500,000 deaths per year. Researchers suspect that very hot liquids irritate or damage the lining of the esophagus. This type of repeated injury likely leads to increased inflammation and leaves the delicate tissues vulnerable to damage from other potential carcinogens, including those contained in tobacco products and alcohol. Tobacco and alcohol use, acid reflux and being over 55 are also considered to be risk factors for cancer of the esophagus. This type of cancer is more common in men than in women.
When it comes to preferences for beverage temperature, Americans and Europeans tend to be more moderate than tea drinkers in Asia, South America and Africa. Considering that 80 percent of tea in the United States is consumed as iced tea, we suspect that added sugar may be as much of a health concern here as the temperatures of hot tea. Still, we think it makes sense to opt for cooler temperatures with any hot beverages in order to protect the hard-working tissues of the esophagus.
Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health.