Sunday, March 31, 2019

A Little Hot Tea Never Hurt Anyone



Or did it? (Btw, I’m hoping to build this into a series about the relative dangers of random shit I hear about out in the world, but I’m a busy person, so we’ll just have to see how it goes.)

The inaugural threat comes courtesy of a coffee-drinking friend who recently expressed concern that my tea habit* could lead to an early demise because of some new study linking hot tea and esophageal cancer. The warning was caveated with a recommendation that I check the specifics before making lifestyle adjustments, so I did just that and will now answer all your burning question on the subject.

Why is it just tea and not coffee?
Because the study only looked at tea drinkers, specifically people living in the Golestan Province in northeast Iran. The region’s high incidence of esophageal cancer makes it a convenient place to conduct such a study, but coffee drinking is not really a thing in Golestan, so tea was the focus. The authors cite previous literature supporting that consumption of overheated drinks of all stripes can mess with your esophageal tissue. So, while the results of this study are about tea, it’s a proxy for throat-scalding liquids in general. (It’s just that coffee drinkers easily gloss over the words “and other hot beverages.” Similar to how I regularly ignore the “1-2 glasses” part of articles about the potential health benefits of wine.)

Does this study tell us anything new?
That depends on your threshold for novelty. The authors proudly proclaim that theirs is the first such study to both “prospectively and objectively” measure tea-drinking temperature. “Prospectively” meaning they started with cancer-free subjects and followed them over a period of time (10 years, not too shabby) to see if cancer developed rather than asking people already diagnosed with cancer about their past tea drinking behavior (which is the quicker and easier but also more bias-ridden approach). “Objective” meaning that, in addition to gathering self-reported tea temperature preferences, researchers measured subjects’ tea with a thermometer.** Ultimately the goal is to bump the International Agency for Research on Cancer (IARC) ranking for drinking beverages at or above 65 C from it’s current status of “probably carcinogenic” to the more confident “carcinogenic.”

What is the proper temperature to drink my morning cup of tea/coffee/hot buttered rum?
Probably safe to drink. Image: TheCulinaryGeek
The big finding in this study was that subjects who drank 700 ml or more of tea at temps of 60 C or hotter had a 90% increase in esophageal squamous cell carcinoma risk. (In headline language that’s “Drinking hot tea nearly doubles your risk of esophageal cancer!”). They didn’t break down the less-than-60 C category any further, so let’s just go with 59 C as the maximum allowable beverage temperature for anyone who cares about not dying.

700 ml is roughly two soda cans volume wise; and 59 C is about 138 F, which is still meaningless because who the hell knows the numeric temperature of their drinks? Well, thanks to the cheapest digital kitchen thermometer sold on Amazon, I now do and will share my wisdom. (Though you’ll still have to rely on my interpretation of the hopelessly subjective qualia of tea temperature desirability.) Below are the highly scientific results:

88.2 C – freshly poured (Really? The water was at a rolling boil and I don’t live at some weird altitude, but okay five-dollar thermometer.)
75.1 C – after five minutes of steeping, will burn your tongue if you take too big a sip
66.4 C – I added some creamer, drinkable but still a tad too warm
58.3 C – the perfect cup of tea
52.7 C – still decent
43.7 C – a bit cold, but not “I forgot I still had half a cup of tea left” cold

A 2008 paper, which I can only imagine was the most exciting and widely-covered research of its day, took a more mathematical approach to determining the optimal serving temperature for hot beverages (paper title: “Calculating the optimum temperature for serving hot beverages”). The authors’ goal was not to prevent cancer but rather to reduce ER visits for the service industry employees who assemble and deliver our hot beverages. Over the course of seven pages of formulas and graphs they concluded that 136 F (57.8 C) was the best bet for balancing consumer preference with the minimizing of third-degree burns.

Should I be concerned about all those cups of ≥60 C tea/coffee/mulled wine I already drank?
I’m not, and I’m pretty committed to hypochondria. The main reason is that esophageal cancer is relatively rare in the US, accounting for only 1% of cancer diagnoses (though I might feel differently if I lived in Iran, northern China, India, or southern Africa, where it’s far more common). Doubling the risk of a something is less impressive when the baseline risk is low. Moreover, things like tobacco and alcohol consumption seem to be bigger risk factors. So don’t beat yourself up about your misspent youth of hot tea drinking.

Moving forward, sure, allowing tea to cool slightly is an easy enough health intervention. But if drinking too hot beverages is the worst of your potentially disease-causing habits, I’d say you’re living a pretty wholesome life.

Are you sure it’s not just the tea itself that causes esophageal cancer?
Nothing in this world is certain. Everything and everyone has the capacity to deceive, disappoint and betray you. But in regards to this particular study, it’s hard to say. While they did also look at how much tea subjects consumed, most of the heavy tea drinkers were also the people who preferred their tea piping hot, so those variables are difficult to untangle. And due to a combination of my own laziness and the authors’ assurance that their study is methodologically superior to its predecessors, I’m opting not to dig too far into the archives on this one. There is mention of animal studies suggesting that certain compounds in hot beverages could be a contributing issue rather than just the temperature. So maybe plain hot water is the safest (and most affordable!) option. You’re welcome to give it a shot, but I’m going to stick with tea.


* I accidentally quit drinking coffee a few years back and now start my days with English Breakfast tea like some kind of commie weirdo pervert.
** The method was to make two cups of tea, one for the subject to sip and comment on and the other to be used simultaneously to take temperature readings. Science!


Title Image: Markus Kniebes


1 comment:

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