Most of us enjoy a good cuppa. And for a cuppa to be good it needs to be hot. But should we cool our relationship with one of our favourite beverages, given that research has linked drinking hot tea to cancer?
Probably not, unless you drink your tea scaldingly hot – in which case you’re increasing your risk of one kind of cancer of the oesophagus.
The link between hot drinks and cancer has been bandied around for decades – the first article proposing it was published in 1939.
But a clear association between drinking scalding hot tea and an increased risk of oesophageal cancer was firmly established in a study published in the British Medical Journal in 2009.
And the hotter the tea, the higher the risk.
How hot is hot?
The study took place in northern Iran, a region where people drink a lot of tea, and they like it hot – as high as 80 degrees Celsius. The area also has one of the highest incidences of squamous cell oesophageal cancer in the world, with around 15 people per 100,000 suffering from the disease.
The researchers found that regularly drinking very hot tea (over 65 degrees Celsius) was associated with an eight times higher risk of oesophageal cancer, while drinking hot tea (60 to 65 degrees) was linked with double the risk.
These tea temperatures are exceptionally hot by our standards, “particularly where people add milk to their tea”, says Professor David Whiteman, head of the Cancer Control Group at QIMR Berghoffer.
“That reduces the temperature considerably.”
And while heat is the factor increasing the risk, nobody really knows exactly how it is having this effect. But the most plausible hypothesis comes down to chronic inflammation as a result of regular scalding hot drinks, says Professor Whiteman.
“It’s known that heat causes inflammation, and inflammation is a factor that’s involved in many cancers in many organs in the body.”
In regular drinkers of hot tea, “that endless cycle of damage and repair can make the cells unstable and prone to mutation that can set up conditions in which cancers can arise”, he said.
But there’s a simple way to reduce the risk.
“Adding milk drops the temp by 5 to 10 degrees immediately … and allowing the tea to sit in the cup for two minutes or so will also take some of that scalding heat out of it and tea can be consumed without causing injury.”
Oesophageal cancer on the rise, but not because of tea
Interestingly, the form of oesophageal cancer affected by hot drinks is on the decline in Australia. It has become much less common as smoking rates have declined, says Professor Whiteman.
But the other form – adenocarcinoma oesophageal cancer – has become much more common recently. And the risk factors for it are not related to a cuppa.
“We’ve done a lot of research on that” says Professor Whiteman. “It’s driven by acid reflux or heartburn, obesity, being male, and smoking. These four driving factors account for 80 or 90 per cent of those cancers.”
And the best thing to minimise risk is to tackle obesity.
“The two things together – having reflux and being obese multiplies the risk, so it’s really better to lose weight if you have reflux – it will help your reflux and it will reduce your risk for cancer.”