In the linked case-control study (doi:10.1136/bmj.b929), Islami and colleagues assess the association between how people drink their tea and the risk of oesophageal squamous cell carcinoma.1

Cancers of the oesophagus kill more than 500 000 people worldwide each year, with the bulk of the disease occurring in discrete populations in Asia, Africa, and South America.2 3 Despite recent increases in the incidence of adenocarcinomas of the oesophagus in industrialised nations,4 5 the most common subtype of oesophageal cancer worldwide is oesophageal squamous cell carcinoma. Tobacco and alcohol are the main causal factors related to oesophageal squamous cell carcinoma in the West, but they are not implicated in non-Western populations that have very high rates of this disease. Nutritional deficiency,6 viral infection,7 and dietary toxins8 have all been postulated as causal factors, although none can fully explain the extraordinary excess of cases of oesophageal squamous cell carcinoma seen in these populations.

Reza Malekzadeh and other authors of this population based case-control study talk about the effect of tea drinking and …