Hot tea and oesophageal (gullet) cancer

It's the temperature of the tea that matters.

As a nation, we love a good cuppa. Morning, noon or night we can often be found cradling a nice cup of tea. But you may have read in the papers recently about a study looking at whether drinking hot tea can cause cancer of the oesophagus.

Well, you don’t need to axe your favourite brew just yet. Because the researchers found that it’s only piping hot tea at over 70 degrees that their study suggested might increase the risk of cancer.

Let’s take a look at the research in more detail.

What they did

The oesophagus is the pipe that takes food from your mouth to your stomach. Oesophageal cancer is the ninth most common cancer in the UK, and it’s often caused by smoking and drinking alcohol.

For this study, the scientists went to a province of northern Iran, called Golestan, where oesophageal cancer is much more common than in the general population.

But people in this region don’t tend to smoke tobacco or drink alcohol. Instead, men and women of all ages drink very hot tea in large quantities – as much as a litre a day.

The researchers compared a group of 300 people who had oesophageal cancer with 571 people who were unaffected (a type of study called a case-control study). They found that people who had oesophageal cancer were more likely to regularly drink tea at very high temperatures than people who didn’t have the disease.

To measure how hot people’s tea was when they drank it, they asked them two questions. Firstly, they asked whether people normally drank tea lukewarm, warm, hot or very hot. And then, they asked people how long they usually waited after pouring their tea until they drank it.

The researchers also did a second study, which looked at tea drinking in the general population of Golestan. They asked nearly 50,000 people to tell them whether they usually drank tea lukewarm, warm, hot or very hot. And then, they poured each person a fresh cup of tea.

As it cooled, the participants tasted the tea and said whether it was too hot, or about the right temperature. Doing this allowed the researchers to find out how accurately people could describe the temperature of their tea.

The results

The scientists published the results of these studies in the British Medical Journal. In the first study, comparing people with oesophageal cancer with healthy people, the scientists found out that people who drank tea hot or very hot were more likely to have oesophageal cancer than people who drank it warm or lukewarm. They also found that people who waited less than 4 minutes before drinking their tea (so it was hotter) had a higher risk than people who waited for 4 minutes or more.

And in the second study, of the general population, they found that most people in Golestan drink their tea at temperatures of more than 60 degrees. They also discovered that people’s descriptions of the temperature of their tea were quite accurate.

How could hot tea increase the risk of cancer?

It’s not entirely clear how hot drinks cause oesophageal cancer, although researchers have put forward a few ideas.   Firstly, very hot drinks might irritate the oesophagus, causing inflammation. In turn, this could kick off processes that damage cells and increase the risk of cancer.

Hot liquid can also cause damage to the lining of the oesophagus, meaning that any cancer-causing substances in our diet can find their way into cells more easily.  Such substances might potentially come from charred food that has been grilled, or, more likely, from opium smoke (a common habit in the region).

Should I stop drinking tea?

The results of this study show us that there might be a link between drinking extremely hot liquids and developing oesophageal cancer.  A key point to stress is that the researchers found that it wasn’t tea itself, or the amount of tea, that increased the risk, but the tea’s temperature. In fact, some research has suggested that certain chemicals in tea – called flavonoids – might have a protective effect against cancer, although this has only been shown in animal tests rather than in humans.

In this research, the scientists found that many people in Golestan were drinking more than a litre of tea per day at temperatures over 60 degrees centigrade.  Studies in the UK have found that the average temperature for drinking tea is between 56 and 60 degrees, much less than the temperature people drink it in Golestan. And we also tend to add milk to our British cuppas, which makes them cooler. So we’re not likely to be very much at risk from drinking hot tea.

But the study gives us an opportunity to do more research to find out for sure whether it’s something people should worry about, particularly if they come from cultures where tea is drunk very hot. Cancer Research UK has been funding another study in the same area of Iran -researchers are following a large group of people over several years and seeing which of them develop oesophageal cancer in the future. This is a powerful type of research because, unlike the study published this month, it doesn’t rely on people remembering how hot their tea usually is, making it more accurate.

If you’re still a bit worried, remember this study isn’t saying don’t indulge in a cuppa – it’s saying that the extreme heat of the drink may be the problem. So, a dash of milk or letting your brew cool down a bit before you drink it deals with that.

Jess