The verdict is out: there is no conclusive evidence showing that drinking coffee can cause cancer, according to the World Health Organization (WHO). But is high temperature in coffee and other beverages truly a cause for concern?
The International Agency for Research on Cancer (IARC) earlier categorized coffee as possibly carcinogenic in its 2B category, listing it alongside substances like lead and chloroform. However, it reversed its former warning based on new results of over 1,000 human and animal studies.
Safety, however, remains a question if the drink is consumed at very high temperatures, with scientific proof showing that drinking coffee, tea and other beverages at about 65 degrees Celsius or higher may cause esophageal cancer.
In countries like China, Iran, Turkey and South America where a traditional drink called maté is consumed at around 70 degrees Celsius, the risk of this cancer climbed with the temperature at which the beverage was drunk.
IARC director Dr. Christopher Wild said that smoking and alcohol consumption are the usual causes of esophageal cancer, especially in high-income nations. However, evidence shows there are positive associations between drinking extra hot beverages and the said cancer.
“The majority of esophageal cancers occur in parts of Asia, South America, and East Africa, where regularly drinking very hot beverages is common and where the reasons for the high incidence of this cancer are not as well understood,” he explained.
Dr. Thomas Sherman of Georgetown University Medical Center told Stuff that studies from the last four to 10 years have narrowed the list of potential dietary factors in esophageal cancer, originally focusing on specific ingredients like caffeine.
“Several of these studies, however, focused on a common factor for all beverages: they can be very hot, and the question was asked whether thermal injury to the esophagus may be the real risk factor,” he said, adding that explanations around thermal injury include both genetic and metabolic processes.
One explanation is that excessively hot drinks can injure the cells lining the throat.
These cells play a crucial role in protecting tissues from being exposed to potential carcinogens in food and the air. Repeatedly inflicting thermal injury on this barrier might let in small levels of foodborne carcinogens, such as alcohol, to impact exposed sensitive tissues.
The risk for esophageal cancer is about 2.4 times higher for those who drink extra-hot beverages compared to those who do not – fortunately a small number, Sherman noted. This is deemed a very low risk compared to known carcinogens, alcohol included.
A study last year discovered that colon cancer patients who drank at least four cups of caffeine-rich coffee every day were 52 percent less susceptible to a recurrence of illness or death by the cancer form, compared to those abstaining from the beverage.
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