Indians love drinking tea - and they like it piping hot, but it is better to wait for four minutes before sipping it, as new research shows that drinking very hot tea can increase the risk of throat cancer.

A study carried out by Iranian researchers and published in the March issue of the British medical Journal shows that people residing in Golestan province of northern Iran, drank lots of hot tea every day and there was a strong indication that drinking very hot tea was linked to a higher risk of cancer of the oesophagus, which is the tube that carries food from the throat to the stomach.

In Europe and America, oesophagus cancer is mainly caused by tobacco and alcohol use and is more common in men than in women.

Oesophagus cancer generally affects smokers and drinkers, but in Golestan province of Iran, which has one of the highest incidence rates for Oesophagus cancer in the world, the residents neither drink or smoke and the disease affected both men and women.

Earlier studies in Golestan have suggested that low intake of fresh fruits and vegetables, low socioeconomic status, and opiumconsumption are associated with a higher risk of oesophageal cancer. In addition, studies have pointed towards the possible role of drinking very hot tea.

An ecological study showed that inhabitants of Golestan drank an average of 1.2 litres of tea daily at a higher temperature than people living in a nearby area with a low incidence of oesophageal cancer.

Iranian researchers led by Dr Farhad Islami and his colleagues from Tehran University of Medical Sciences, set out to find if there was a connection between drinking hot tea and oesophageal cancer.

The researchers carried out a study on 300 people diagnosed with oesophageal cancer and compared them with a group of 570 people from the same area. All the participants drank an average of 1.2 litres of tea everyday.

The research team was joined by researchers from the US, the UK, France and Sweden and they found out that nearly 98 per cent of the participants drank over one litre a day of black tea regularly.

The analyses took into account factors that could affect results (potential confounders), such as vegetable intake and tobacco use. They also took in to account opium use, ethnicity, and indicators of socioeconomic status, such as education, car ownership and length of residence in rural areas.

They measured the temperature of tea drunk by the participants. To achieve this they prepared a fresh cup of tea for each participant and measured the temperature of the tea using a digital thermometer.

When the temperature was 75°C the participants were asked to sip the tea and say whether that was the temperature at which they usually drank tea. If not, the tea was allowed to cool to 70°C and the question was asked again. This procedure was repeated, at 5°Cintervals, until the temperature at which tea was usually drunk was reached.

This method for measuring the temperature of tea showed good reliability when tested in the pilot phase of the cohort study.

The researchers found out that nearly 98 per cent of the participants drank black tea regularly, with a mean volume consumed of over one litrea day. 39 per cent of participants drank their tea at temperatures less than 60°C, 38.9 per cent at 60-64°C, and 22 per cent at 65°C or higher.

A moderate agreement was found between reported tea drinking temperature and actual temperature measurements. The results of the case-control study showed that compared with drinking lukewarm or warm tea, drinking hot tea or very hot tea was associated with an increased risk of oesophageal cancer.

Likewise, they found out that the faster the time taken to drink the tea after being poured, increased the risk of oesophageal cancer compared to people who drank at a later time.

The results of the case-control study showed that comparedwith drinking lukewarm or warm tea, drinking hot tea or very hot teawas associated with an increased risk of oesophageal cancer.

Indian tea drinkers consume about 755.52 million kilos of tea every year, which is about 0.7 kg per capita with the highest ranking in consumption being Maharashtra while the largest tea producing states, West Bengal and Assam ranked 9th and 14th respectively.

In the UK, the consumption of tea per capita is 2.3, Ireland at 1.5, and the US at 0.2kg per capita.

This month Lenore Arab, professor of medicine at the David Geffen School of Medicine, conducted a study and found out drinking tea can reduce the threat of stroke by as much as 21 per cent.

Experts however caution and say that the risk of oesophageal cancer may not be linked directly with drinking very hot tea but maybe any hot beverage or food and more research will have to be conducted in this area.