Fun fact: according to CNN, on New Year’s Day 90% of the US never got above freezing.

Second fun fact: on my way in to work this morning I passed an enormous fire burning a couple hundred yards from where the train runs. I Googled it to see what was happened and discovered it was a gas main that caught on fire, and they realized that shutting the gas off (normal procedure I assume) would have made thousands of people in the area lose heat. With temps hitting -6F, they couldn’t justify the damage so they let the fire burn for two days while they figured out another way of putting it out.

In other words, it’s cooooooooooold out there.

With a record cold snap on our hands and the worst yet to come this weekend, I’ve been spending a lot of time warming up. This means a lot of hot tea and hot coffee have been consumed, which reminded me of a factoid I’d heard a few months ago but never looked in to. Someone had told me that drinking hot beverages was a risk factor for esophageal cancer, but when pressed they couldn’t tell me what was meant by “hot” or how big the risk was. I figured this was as good a time as any to look it up, though I was pretty sure nothing I read was going to change my behavior. Here’s what I found:

1. Hot means HOT When I first heard the hot beverage/cancer link, my first thought was about my morning coffee. However, I probably don’t have to worry much. The official World Health Organization recommendation is to avoid drinking beverages that are over 149 degrees F. In case you’re curious, Starbucks typically servers coffee at 145-165 degrees, and most of us would wait for it to cool for a minute before we drank it.
2. Temperature has a better correlation with cancer than beverage type So why was anyone looking at beverage temperature as a possibly carcinogen to begin with? Seems a little odd, right? Well it turns out most of these studies were done in part to rule out that it was the beverage itself that was causing cancer. For example, quite a few of the initial studies noted that people who drank traditional Yerba Mate had higher esophageal cancer rates than those who didn’t. The obvious hypothesis was that it was the Yerba Mate  itself that was causing cancer, but then they noted that repeated thermal injury due to scalding tea was also a possibility. By separating correlation and causation, it was determined that those who drink Yerba Mate (or coffee or other tea) at lower temperatures did not appear to have higher rates of esophageal cancer. Nice work guys.
3. The risk has been noted in both directions So how big a risk are we looking at? A pretty sizable one actually. This article reports that hot tea drinkers are 8 times as likely to get esophageal cancer as those who drink tea at lower temperatures, and those who have esophageal cancer are twice as likely to say they drank their tea hot before they got cancer. When assessing risk, knowing both those numbers is important to establish a strong link.
4. The incidence rate seems to be higher in countries that like their beverages hot It’s interesting to note that the US does not even come close to having the highest esophageal cancer rates in the world. Whereas our rate is about 4.2 per 100,000 people, countries like  Malawi have rates of 24.2 per 100,000 people. Many of the countries that have high rates have traditions of drinking scalding hot beverages, and it’s thought that combining that with other risk factors (smoking, alcohol consumption, poverty and poorly developed health care systems) could have a compounding effect. It’s not clear if scalding your throat is a risk in and of itself or if it just makes you more susceptible to other risks, but either way it doesn’t seem to help.
5. There is an optimum drinking temperature According to this paper, to minimize your risk while maximizing your enjoyment, you should serve your hot beverages at exactly 136 degrees F. Of course a lot of that has to do with how quickly you’ll drink it and what the ambient temperature is. I was pretty impressed with my Contigo thermos for keeping my coffee pretty hot during my 1.5 mile walk from the train station in -3 degrees F this morning, but lesser travel mugs might have had a problem with that. Interestingly I couldn’t find a good calculator to track how fast your beverage will cool under various conditions, but if you find one send it my way!

Of course if you really want to cool a drink down quickly, just move to Fairbanks, Alaska and throw it in the air:

Stay warm everyone!