As a tea-drinking Brit I was fascinated by a study about tea drinking in Northern Iran concluding that drinking very hot tea is strongly associated with higher risk of oesophageal cancer.
Digging in further, I was struck by a number of points:
- The article I first noticed, by Karen Kaplan of the Los Angeles Times, was very clearly written and didn’t mangle the facts or interpretations. Such clarity is unusual and deserves a commendation. Read the article for the details – I don’t need to repeat.
- The scale of the study was unusually large compared with many medical studies, including some that draw dubious conclusions from a very small data set. The research team (from England, France, Sweden and the U.S.) matched 300 cancer patients with 571 healthy controls who had similar demographics. These groups are only a small fraction of the entire database of nearly 50,000 people in Golestan province whose tea drinking habits have been studied, so we can expect future refinement and expansion of results.
- The original article in the BMJ (formerly the British Medical Journal), BMJ 2009;338:b929, is a well-written source document, complete with properly explained tables and a video.
This is a good example of a well researched and reported project. The results are made available under an open access Collective Commons License, that doubtless encourages completeness.
After evaluating the details, I decided to review my own tea and coffee rituals. The study concluded that the most likely causal mechanism is the temperature, so regardless of what hot liquid you drink it might be a good to be cautious about temperature. I don’t drink anywhere near the quantity of hot liquids that the study participants imbibe daily (nearly 1.2 liters on average – that’s over 2.1 British pints or 2.5 U.S. pints), but the damage may be cumulative and I want to be a tea drinker for many more years. It seems that my latte drinks are cool enough, but I should probably wait for a few minutes after brewing to drink my tea at around 140 degrees Fahrenheit. Perhaps I’ll start to put the tea cosy on after the first cup, but I don’t think I can bring myself to stop warming the teapot. My wife is the smart one – she’s always preferred to cool down her tea with water from the tap.