IARC rates coffee as not carcinogenic, but warns of very hot drinks
For a long time, coffee was considered to be rather harmful to health and there was also speculation about possible connections with cancer. In a recent study, the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) now comes to the clear conclusion that coffee has no carcinogenic effects. On the contrary: Coffee can apparently even protect against two forms of cancer. However, according to the scientists, very hot drinks are generally associated with an increased risk of esophageal cancer. The researchers published their results in the specialist journal "The Lancet Oncology".
In their current study, the IARC scientists examined possible correlations between cancer risk and the consumption of coffee, mate tea and other very hot drinks. They come to the conclusion that "there is no conclusive evidence of the carcinogenic effects of coffee". With mate tea, just like with other hot drinks, the consumption temperature played a decisive role in relation to the risk of cancer. The study results "suggest that the consumption of very hot drinks is a likely cause of esophageal cancer and that the temperature, rather than the drinks themselves, appears to be responsible," emphasizes Dr. Christopher Wild, director of the IARC.
More than 1,000 studies on cancer risk from coffee consumption evaluated
The international working group of 23 IARC scientists has commissioned WHO to assess the carcinogenicity of coffee, mate tea and very hot drinks. To this end, the researchers analyzed the results of numerous older studies worldwide. According to the results, coffee consumption can no longer be classified as “possibly carcinogenic to humans” (1991 IARC assessment). "After thoroughly reviewing more than 1,000 human and animal studies, the working group found that there was insufficient evidence to prove the carcinogenicity of coffee consumption," the IARC said.
Reduced risk with two types of cancer
According to the researchers, many epidemiological studies have shown that coffee does not pose an increased risk of breast cancer and cancer of the pancreas or prostate. In addition, coffee consumption is associated with a reduced risk of cancer of the liver and uterus, reports the IARC. With more than 20 other types of cancer, the researchers were not able to make a scientifically reliable assessment, so it remains unclear to what extent coffee consumption influences the risk of illness.
Temperature is critical to cancer risk
In their analysis, the researchers found that mate tea had no carcinogenic effects in animal experiments and epidemiological studies as long as it was drunk cold. The consumption of mate tea is particularly widespread in South America, but in Europe and North America the tea made from the dried leaves of the Ilex paraguariensis has recently also enjoyed increasing popularity. Traditionally, mate is drunk very hot (at around 70 ° C), but can also be consumed warm or cold, explain the IARC researchers. For the very hot tea, as well as for other beverages that are drunk at correspondingly high temperatures, the result is "probably carcinogenic", according to the result of the working group.
Also very hot water with carcinogenic effects?
For the very hot drinks, the evaluated epidemiological studies generally showed a positive association with cancer of the esophagus. "Studies in places like China, the Islamic Republic of Iran, Turkey and South America, where tea or mate is traditionally drunk very hot (at around 70 ° C), have found that the risk of esophageal cancer increases with the temperature of the drinks," according to the IARC. In experiments with animals, there would have been evidence of a carcinogenic effect even for very hot water.
Risk of esophageal cancer from very hot drinks
"Smoking and alcohol remain the main causes of esophageal cancer, especially in many high-income countries (...), but the majority of esophageal cancer cases occur in parts of Asia, South America and East Africa, where regular consumption of very hot drinks is common" , says the IARC director Dr. Wild.
The reason for the high incidence of this type of cancer is so far unclear and the consumption of very hot drinks could possibly play a role here. According to the IARC, esophageal cancer is the eighth most common cancer worldwide and was one of the deadliest forms of cancer in 2012 with around 400,000 deaths. The proportion of esophageal cancer cases that can be linked to the consumption of very hot drinks remains unclear, according to the researchers, but could be considerable. (fp)