Very hot tea and coffee may triple the risk of oesophageal squamous cell carcinoma, with researchers suggesting cooler drinks could prevent hundreds of UK cases each year.
Drinking your tea or coffee piping hot could more than triple your risk of oesophageal squamous cell carcinoma, according to a study of almost one million UK adults.
The prospective analysis found people who preferred their drinks “very hot” had more than three times the risk of oesophageal squamous cell carcinoma (SCC) compared with those who preferred warm drinks, after accounting for the number of hot drinks consumed.
“Studies in Asia, Africa, South America and the Middle East have consistently shown that tea or mate [a regional caffeinated herbal drink] drunk at very high temperatures (~70°C) increases oesophageal cancer risk, but evidence is limited for drink temperatures typical of Western populations,” the researchers wrote.
“This large UK study of middle-aged adults, amongst whom hot drinks are widely consumed, provides clear evidence that temperature and frequency of hot drink consumption represent useful targets for oesophageal SCC prevention.”
Their study, published in the International Journal of Cancer, pooled data from 977,282 participants in the Million Women Study and UK Biobank. Over average follow-up periods of 14.2 and 11.1 years respectively, researchers recorded 2348 oesophageal cancers, including 1045 SCCs and 1303 adenocarcinomas.
After adjustment for consumption frequency, drinking beverages “very hot” rather than warm was associated with a more than threefold higher risk of SCC (RR 3.17, 95% CI 2.49-4.03).
Even those who preferred their drinks “hot” had a 69% higher risk (RR 1.69, 95% CI 1.36-2.11). In contrast, there was no material association between drink temperature and oesophageal adenocarcinoma.
Quantity also appeared to matter independently of temperature. Drinking six or more hot drinks a day, compared with fewer than six, was associated with a 71% increased risk of SCC after adjustment for preferred temperature (RR 1.71, 95% CI 1.51-1.94). The corresponding relative risk for adenocarcinoma was 1.19 (95% CI 1.06-1.33).
High consumption was common, with 43% of Million Women Study participants and 44% of UK Biobank participants reporting six or more hot drinks a day, while 13% and 17%, respectively, said they preferred their drinks very hot.
The researchers noted that the International Agency for Research on Cancer has classified beverages consumed above 65°C as “probably carcinogenic to humans”, but evidence at temperatures more typical of Western countries had been limited.
They said tea and coffee in the US and UK were commonly consumed around 60°C and the new findings suggested increased SCC risk may occur below the IARC’s 65°C threshold.
However, the researchers did not directly measure beverage temperature, relying instead on participants describing their preference as warm, hot, or very hot.
The association was not materially altered by adjustment for factors including smoking and alcohol consumption and was also evident among never-smokers and light drinkers. Results were broadly unchanged when the first five years of follow-up were excluded, reducing concerns that preclinical disease had influenced participants’ drinking habits.
Nor did the type of drink appear to explain the findings. Similar associations were seen regardless of whether participants predominantly drank tea or coffee, and adding milk did not materially modify the temperature-associated risk.
“The most likely mechanism is thermal injury, which may impair mucosal integrity and promote carcinogenic processes,” the researchers wrote.
“We clearly demonstrated that any association with drink temperature was confined to SCC.
“This observation would appear to support a thermal injury mechanism since such cancers typically arise from squamous cells in the upper two-thirds of the oesophagus which would be expected to be most susceptible to the effects of hot liquids.”
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Assuming the association was causal, the researchers estimated that 14% of oesophageal SCC cases in the UK could be prevented if people who preferred “very hot” drinks instead drank them “hot”. Based on national incidence rates, that would equate to about 440 fewer cases each year, the researchers said.
“Although the prospective design eliminates the potential for biased recall of exposures in those with a diagnosis of oesophageal cancer, it remains possible that preclinical symptoms affected behaviours and reporting of drink temperature at baseline, which could have biased the observed associations,” they wrote.
“However, analyses excluding the first five years of follow-up yielded similar results to those observed overall.”
The researchers said their study provided “robust evidence that drink temperature as well as frequency of hot drink consumption are likely to be substantial risk factors for SCC”.
“Our findings suggest that reducing drink temperature in populations where tea and coffee are frequently consumed could offer an important means of SCC prevention,” they concluded.
