WEEKEND COLUMNISTS I live with an Irishman, which means that at home we drink Barry’s Tea. In my early married life I was “not allowed” this Irish brand, as apparently I did not appreciate it enough. Now, there is a supplier in Glasgow and we no longer have to import boxes of the elusive blend from Dublin. I am still not allowed to make it, however, as there is a very specific brewing time – at least five minutes, so I’m told.
This method of preparation may be a good thing, for in the process of brewing, then adding milk, the tea is never piping hot. According to a recent study in the British Medical Journal, the temperature of tea could be a risk factor for cancer. The habit of drinking of hot tea in Iran, where the study was conducted, seemed to increase the likelihood of developing oesophageal cancer.
More than 80 per cent of oesophageal cancers are diagnosed in the developing world; men, too, are at increased risk, accounting for almost two-thirds of sufferers. In Iran, there are 17.6 cases per 100,000 of the male population; in China, the rate is 24; and in England, it is 14.
Why? The cited potential causative factors in oesophageal cancer have been many and varied: alcohol, tobacco (chewed or smoked), a diet without fresh fruit and vegetables, or with smoked foods, along with the habit of drinking very hot fluids. But this association between tea and cancer is very hard to prove.
The study in the BMJ was a case control study, where people who had developed oesophageal cancer were “matched” with people who did not have oesophageal cancer, and their past tea-drinking habits compared. The researchers found that this population drank their tea black and hot, with the strongest association with oesophageal cancer where tea was drunk at high temperatures shortly after it was brewed. But asking people to describe how hot they took their tea 10 years ago in a retrospective study of this sort is less likely to be reliable than data collected about what is happening now. The latter “prospective” type of study – following a group of people over time from a point before they have developed a condition – is, however, usually expensive and time-consuming.
The new BMJ research is good, but it raises further questions: is it the temperature of the drink or the specifics of this drink taken at high temperature which is associated with oesophageal harm? Would this be mitigated by the addition of cold milk? Or is the length of brewing time potentially culpable? Something to debate, probably over tea.
Margaret McCartney is a GP in Glasgow
For lively discussion of the latest medical issues go to Margaret McCartney’s blog at blogs.ft.com/mccartney
