The main finding of the study, part-funded by Cancer Research UK, isn’t new. Drinking very hot drinks may raise the risk of oesophageal cancer, and this study adds to the limited evidence by studying a large group of people from Iran.
But how hot is hot? And is that raised risk something to worry about?
What did the study do?
The study, published in the International Journal of Cancer, included people living in Iran and asked about their tea drinking habits, measuring the temperature at which they preferred to drink tea at the beginning of the study.
Researchers checked back with these people 10 years later on average to see how many people had developed a certain type of oesophageal cancer. And if their tea-drinking habits played any role in who developed it.
What did the study show?
People who preferred drinking their tea at or above 60C (140F) had an increased risk of oesophageal cancer, compared to those who preferred drinking their tea below 60C. Crucially, 60C is likely to be a lot hotter than most cups of tea.
But a person’s risk of oesophageal cancer can depend on many factors and the study didn’t look at all of these. The researchers did look at if people had ever smoked or were current smokers, but not how much people had smoked, or for how long. They also didn’t look in detail at their eating habits, which can also affect oesophageal cancer risk.
When news stories say hot tea ‘doubles oesophageal cancer risk’ or increases it ‘by 90%’, it’s important to remember these are relative risks and should be treated with caution, as we’ve blogged about before.
To really understand risk, it needs to be put into context. And that means factoring in how common the disease is overall. In the part of Iran where this study took place, oesophageal cancer rates are high, so something that raises this risk even a little bit will have a larger impact.
But here in the UK, oesophageal cancer is less common, accounting for 3 in 100 new cases of cancer.
So even if very hot drinks might increase someone’s risk of oesophageal cancer, the chances of them developing the cancer are still low, because it isn’t very common in the UK.
So, what might these results mean for you?
It’s important to remember that this study was based on people living in Iran. The traditions and types of tea drunk in Iran may be very different to how most people in the UK drink their tea. For example, the people in the study were drinking green or black tea, where in the UK, most people add cold milk to their tea, which will quickly cool it down.
If you’re leaving your tea to cool for a few minutes before drinking it, even while it’s brewing, or adding cold milk, it’s unlikely that you’re increasing your risk of oesophageal cancer.
And if you’ve accidentally burnt your mouth on a hot drink a few times before, this is unlikely to make much difference.
The researchers say in their study that beverages are usually consumed at more moderate amounts and temperatures in Western populations, like in the UK.
Perhaps most importantly, research shows that there are other things you can do to reduce your risk of oesophageal cancer that will have a bigger impact than ditching your morning brew. Not smoking, keeping a healthy weight and cutting down on how much alcohol you drink are worth more attention than the temperature of your tea.
What’s next for research into this link?
Some studies, based in other places where traditionally people drink very hot drinks, such as China, Turkey and South America, have found a similar link. But more research is needed to understand how hot drinks might affect risk. We’re also funding research trying to track down previously unknown causes of cancer in parts of the world with high rates of certain cancers, including oesophageal cancer.
So far, researchers suggest hot drinks might cause damage by burning cells. This may lead to inflammation that makes it more likely that cancer develops. These damaged tissues may also become more vulnerable to other things that can cause cancer, like chemicals in tobacco smoke.
But, as long as you’re enjoying your tea at a comfortable temperature and leaving it to cool for a bit before you drink it, you shouldn’t worry about increasing your risk by drinking hot drinks.
Georgina Hill is a health information officer at Cancer Research UK
Islami, F., et al (2019) A prospective study of tea drinking temperature and risk of esophageal squamous cell carcinoma. IJC. DOI: 10.1002/ijc.32220