Very Hot Tea and Esophageal Cancer Risk: What IARC Says

Short answer: in 2016 the International Agency for Research on Cancer (IARC, part of the World Health Organization) classified drinking very hot beverages as "probably carcinogenic to humans" (Group 2A), based on esophageal cancer. [1] IARC's director said it is the temperature, rather than the drinks themselves, that appears to be responsible. [1] Information only; this is not personal advice. Ask a clinician if you have swallowing trouble or other symptoms that worry you.

How the sources define the terms

What IARC found

IARC's 2016 press release describes studies in places such as China, Iran, Turkey and South America, where tea or mate is traditionally drunk very hot, which found that the risk of esophageal cancer increased with the temperature of the drink. [1] IARC called this limited evidence from epidemiological (population) studies, and said there was also limited evidence in animals for very hot water. [1] Drinking mate at temperatures that are not very hot was not classifiable (Group 3), because the evidence was inadequate. [1] IARC said the share of esophageal cancers that may be linked to very hot drinks is not known. [1]

What later studies add

These studies show an association. They cannot prove that heat alone causes cancer in an individual.

What this does and does not say about herbal teas

Proper evidence not found for a herbal-tea-specific effect. The IARC release and the studies we read concern tea, mate and other hot drinks; the abstracts we read do not separate herbal teas (tisanes) from Camellia tea, so we cannot say whether herbal infusions behave differently. [1][3] The concern in these sources is temperature, not an ingredient. IARC's text also reports no conclusive evidence that coffee causes cancer, and no conclusive evidence for mate at temperatures that are not very hot. [1]

Limits and uncertainty

IARC's classification describes the strength of evidence that something can cause cancer, not how large the risk is. [1] Smoking and alcohol are major causes of esophageal cancer, according to IARC, which makes careful study design important. [1] Study temperatures and drinking habits vary by region.

Safety and who should ask

Burns from very hot drinks are a separate concern we did not research here. Anyone with difficulty swallowing or other symptoms that worry them should talk to a clinician. For general herbal tea safety see herbal tea and extract safety and yerba mate; for true tea see black tea. Back to herbal tea vs true tea.