Iranian scientists find evidence of link between oesophageal cancer and 'extremely hot tea'
Iranian researchers appear to have found a link between drinking extremely hot tea and a person's risk of cancer of the oesophagus (foodpipe).
However Cancer Research UK said the study only looked at a small number of people and didn't prove a cause-and-effect relationship.
The Iranian study, which is published on bmj.com, found that oesophageal cancer appeared to be more common amongst people who drank black tea at a temperature of 70 degrees Celsius or more.
The team of scientists studied the tea drinking habits of 300 people in northern Iran who had been diagnosed with oesophageal squamous cell carcinoma (OSCC), the most common form of the disease.
These participants were compared with a further 571 healthy volunteers from the same area.
Tea drinking is particularly widespread in the northern Iranian province of Golestan, while rates of smoking and alcohol consumption - both of which are well-known risk factors for OSCC - are low.
Golestan Province has one of the highest rates of OSCC in the world and the researchers theorised that this may be linked to the practice of regularly drinking tea at high temperatures.
All of the people involved in the study claimed to drink black tea on a regular basis, with a typical person consuming over one litre of tea per day.
Researchers found that people who consumed very hot tea (70 degrees Celsius or more) were eight times more likely to develop oesophageal cancer than those who consumed warm or lukewarm tea (65 degrees Celsius or less).
Meanwhile, those who consumed hot tea (65 to 69 degrees Celsius) faced a twofold risk of the disease compared with those who drank warm or lukewarm tea.
Drinking tea less than two minutes after pouring - ie when it is at its hottest - was found to be associated with a fivefold increased risk compared with drinking tea four or more minutes after pouring.
The researchers found no evidence of a link between the actual amount of tea consumed by a person and their risk of cancer.
However, writing in an accompanying editorial, David Whiteman from the Queensland Institute of Medical Research in Australia insists that tea-drinkers should not be alarmed, although he agreed that any hot foods or drinks should be allowed to cool a little before swallowing.
The average person in the UK has previously been shown to prefer their tea in the 56 to 60 degrees Celsius temperature range, which the Iranian study suggests poses little risk.
Dr Whiteman said that consumers should not be deterred from drinking tea and merely recommended avoiding scalding hot food and drink.
He wrote: "We should follow the advice of Mrs Beeton, who prescribes a five to ten-minute interval between making and pouring tea, by which time the tea will be sufficiently flavoursome and unlikely to cause thermal injury."
Oliver Childs, Cancer Research UK's senior science information officer, said: "Tea drinking is part of many cultures, and these results certainly don't point to tea itself being the problem. Although this study is small, it does provide some evidence that a regular habit of eating and drinking very hot foods and drinks could increase your risk of developing cancer of the oesophagus (food pipe). People in this region of northern Iran often drink very hot tea as part of their daily routine. We're a nation of tea lovers in the UK, but we don't tend to drink tea at such high temperatures and we usually add milk, which cools it down. "The most important risk factors for oesophageal cancer are smoking and drinking alcohol. So to reduce your risk give up smoking, limit alcohol and eat plenty of fruit and vegetables to help keep a healthy bodyweight."
Islami, F., Pourshams, A., Nasrollahzadeh, D., Kamangar, F., Fahimi, S., Shakeri, R., Abedi-Ardekani, B., Merat, S., Vahedi, H., Semnani, S., Abnet, C., Brennan, P., Moller, H., Saidi, F., Dawsey, S., Malekzadeh, R., & Boffetta, P. (2009). Tea drinking habits and oesophageal cancer in a high risk area in northern Iran: population based case-control study BMJ, 338 (mar26 2) DOI: 10.1136/bmj.b929