Tea drinking habits and oesophageal cancer in a high risk area in northern Iran: population based case-control study

Altitude alters the boiling point of water, meaning that Zimbabweans living in Harare (1472m) brew their Tanganda tea at approximately 90°C, Tibetans living in Lhasa (3658m) might take their Yak butter tea at approximately 74°C and Bolivians living in El Alto (4058m) are accustomed to brewing their coca tea at approximately 72°C. Iran is a country of geographical highs and lows, with an average altitude of 1200m ranging from 5628m at the Damavand summit in the central Alborz Mountains to 56m above sea level in the Lut Desert. Gonbad city, featured in this article(1), is situated at 187m, meaning that their preferred black tea will typically be boiled to approximately 99°C, while in Tehran, at approximately 1500m, black tea will be boiled at approximately 90°C. We wonder whether altitude might be a protective factor for the development of oesophageal carcinoma in large-volume hot-tea-drinking nations. If this study had been carried out in Tehran, perhaps an altitude effect would have negated the apparent effect of tea temperature in inducing oesophageal carcinoma.

Secondly, with the widely recognized health implications of human-induced climate change and the health co-benefits of climate change mitigation strategies(2) we propose that a more discerning approach to our hot beverages may both reduce the risk of developing oesophageal carcinoma and reduce our carbon footprints. Experts recommend that green tea be brewed at 80°C, coffee at 90°C and black tea at 100°C.

If we were to utilise intelligent kettles with variable temperature control we might reduce the energy consumption and CO2 emissions produced when brewing tea, coffee and hot beverages by 10-20%. In this case, dealing with climate change could have the lucky co-benefit of reducing the incidence of oesophageal carcinoma in hot beverage drinkers. If, however, we fail to deal adequately with the growing climate crisis perhaps rising sea levels will force more of us to move to the protective safety of the hills.

1.Islami F, Pourshams A, Nasrollahzadeh D, Kamangar F, Fahimi S, Shakeri R, Abedi-Ardekani B, Merat S, Vahedi H, Semnani S, Abnet CC, Brennan P, Møller H, Saidi F, Dawsey SM, Malekzadeh R, Boffetta P. Tea drinking habits and oesophageal cancer in a high risk area in northern Iran: population based case-control study. BMJ. 2009 Mar 26;338:b929.

2.Haines A, Kovats RS, Campbell-Lendrum D, Corvalan C. Climate change and human health: impacts, vulnerability, and mitigation. Lancet. 2006 Jun 24;367(9528):2101-9.

Competing interests: None declared