TEHRAN, March 27 (Xinhua) -- Drinking hot tea at a temperature of 70 degrees Celsius or more can substantially increase the risk of throat cancer, Iranian researchers said on Thursday.

    The research, published in the British Medical Journal, was carried out in northern Iran, where a large amount of hot tea is consumed every day.

    Oesophagus cancers kill more than 500,000 people worldwide each year and oesophageal squamous cell carcinoma (OSCC) is the commonest type.

    Previous studies have linked alcohol and tobacco with oesophagus cancers which is more common in men than in women, and now drinking hot beverages may also cause such cancers, according to the research.

    Golestan province in northern Iran has one of the highest rates of OSCC in the world, but smoking rates and alcohol consumption are low, and women are as likely to have the same diagnosis as men. Tea drinking, however, is widespread, so researchers set out to investigate a possible link between tea drinking habits and risk of OSCC.

    They studied the tea-drinking habits of 300 people diagnosed with OSCC and a matched group of 571 healthy men and women from the same area. Nearly all participants drank black tea regularly, consuming more than an average of one litre each day.

    Compared with drinking warm or lukewarm tea at a temperature of65 degrees Celsius or less, drinking hot tea, between 65 and 69 degrees, was associated with twice the risk of oesophageal cancer, and drinking very hot tea at 70 degrees or more, was associated with an eight-fold increased risk.

    Likewise, compared with drinking tea four or more minutes after being poured, drinking tea less than two minutes after pouring was associated with a five-fold higher risk.

    "Our results show a strong increase in the risk of OSCC associated with drinking hot or very hot tea," the researchers said, suggesting people should wait a few minutes before drinking a cup of freshly-boiled tea.

    This report also lends support to the notion that thermal injury may be a cause of epithelial cancers, though the way in which heat promotes tumour development is not clear.