“Caution: Contents Hot!”
The ubiquitous warning label reminding us that our hot things are hot.
As the story goes, an ill-fated woman discovered the hard way in a McDonalds parking lot in 1994 that hot coffee spilled on the lap causes burns. On the one side, don’t spill your coffee. On the other, why are you serving me lava-hot liquids that inflict 2nd degree burns? The lawsuit that ensued this incident settled in favor of the victim. She received one full day of McDonald’s coffee-sale profits (over two million dollars initially, however later lowered two a six-figure payout).
Years and dollars gone, you can still walk into any McDonalds today and find that the coffee is the same temperature (190 Fahrenheit) that it was at the time of the infamous ’94 episode, an event dubbed by experts as the “Double Ouch McOuch Hot Coffee Kerfuffle of ’94.”
Yes, it is true – nothing has changed since the event. Nothing aside from the addition of a warning label. Why is that? Well frankly, people prefer their drinks hot. Are we thrill seekers, living life on the edge of 2nd degree burns and big-dollar payouts? Madness? Masochism? It’s no joke, we like our teas and coffees at injuriously hot temperatures (check the graph).
I wanted to explore this topic a bit, and perhaps find some potential upsides to risking tissue damage which could explain why we appear to innately prefer hot beverages over tepid ones. I ended up finding some interesting stuff.
For drinkers of hot tea, the benefits can range from high antioxidant capacity, to more caffeine (debatable if that’s good or bad, but we’ll talk about it), and even psychosocial benefits, including a greater sense of empathy and kindness for strangers. So, let’s unpack a few of these steamy-hot upsides to preparing and consuming your tea hot.
More anti-oxidant power
The capacity of tea polyphenols to combat free radicals and reduce oxidative damage in our bodies is a well-documented phenomenon. Numerous forms of chronic disease, namely cancer, is caused by excessive exposure to carcinogens that create free radicals in cells that damage proteins, cell membranes, DNA, etc. . Due to a plentiful stock of antioxidant compounds in tea (polyphenols), consuming tea can help combat and neutralize harmful free radicals, reducing our risk of developing certain diseases. But, tea polyphenols are extracted differently at different temperatures.
Finicky compounds they are, scientists have long been unable to identify exactly how polyphenol extraction is optimized. Though still not an exact science, there is a reoccurring theme with water temperature and polyphenol extraction. Here are findings from a few recent studies:
- A 2017 study concluded that 4 different commercial green teas all had the highest antioxidant capacity when infused with 80 degree Celsius (176 Fahrenheit) water temperature . 80 degrees Celsius (176 Fahrenheit) was found again to be the optimal temperature in several other studies [3,5].
- Tea’s most potent natural antioxidant, EGCG, was extracted at over three times the rate in 90 degree Celsius (194 Fahrenheit) water compared to 4 degrees Celsius water . A June 2018 study found optimal extraction conditions for EGCG in green tea to be at 85 degrees Celsius (185 Fahrenheit) .
- 90 degrees Celsius (194 Fahrenheit) water for 5 minutes was found to be optimal for antioxidant extraction in three studies using white and green teas [11,12,13].
- One study found 99 degrees (210.2 Fahrenheit) to be optimal . 98 degrees (204.8 Fahrenheit) in another . However, some research has shown that boiling hot water (100 C/ 212F) can degrade EGCG leading to less total antioxidant capacity [7,8,9].
- Two studies showed greater antioxidant extraction for cold water than hot water, but only after an infusion time of several hours [17,18].
Despite the variable data, however, we at least know that hot water extracts antioxidants more efficiently than tepid or cold water when measuring under constrained timeframes. In other words, if you’re looking for a quick hit of antioxidants, hot infusion is the way to go.
Grant me, if you would, one quick blast of ifs ands & buts before we move on from antioxidants;
- Different tea types possess different types of tea polyphenols with their own distinct characteristics. For example, green tea mainly has EGCG, black tea has high amounts of theaflavin digallate and thearubigans, and oolong and white teas uniquely possess methylated catechins, such as EGCG3’Me. All of these compounds will infuse into water and biodegrade at different temperatures in different water types.
- The products of degradation (called metabolites/catabolites) of various tea polyphenols will look different, and possess their own antioxidant capacities. These metabolites can then react with other dietary compounds and gut microbiota in the GI tract to produce brand new compounds possessing their own bioactive behaviors.
- We don’t well understand the bioavailability (the usefulness) of these polyphenol metabolites, particularly with respect to their bioavailability in the brain.
- In a subset of cases, cell damage and subsequent cell death is actually what the body needs, meaning that fighting free radicals with antioxidants is not ideal in some cases. However, those cases are in the minority. I plan to address this topic in a blog of its own soon.
Caffeine is much more structurally stable than tea polyphenols, meaning caffeine extraction is more consistent and measurable than the lawless bedlam of polyphenol extraction. The consistent trend reflected in the literature is that hot water and long infusion times lead to higher caffeine extraction rates [6,14].
I snipped a data table from a recent study that measured caffeine extraction from white tea using different water temperatures. Caffeine increased (almost exponentially) with increasing water temperature (60, 70, 80, 90, 98 degrees Celsius/ 140, 158, 176, 194, 204.8 Fahrenheit) and increasing infusion time (3, 5, 7, 10, 15 minutes from left to right. Quantities measured as mL/L). As you can see, the hotter and longer the infusion, the more caffeine extracted from the leaves. Finally we have some nice clean data for the whole family to enjoy…
Whether high caffeine content is the right or wrong choice, of course, depends on what time it is, and how sensitive an individual is to the compound. If you want to kick-start your morning with a blast of stimulants to the face, then turn up the water to a roaring boil (I won’t judge. I’m there with you). On the other hand, if it’s 10pm, and you are watching re-runs of Lost with the kids for educational purposes, perhaps consider a cold-brew infusion for less caffeine extraction.
Very short disclaimer about caffeine: Intake of caffeine in excess (though yet undefined) dosages likely takes a toll on human health (much like the show Lost).
The issue with caffeine is that it can keep you up at night. This is proving to be a more significant health risk than previously thought, as an increasing body of data points to the critical importance of quality sleep to overall health. So, if caffeine keeps you up later than you want to be up, I advise cutting back and/or incorporating mindfulness meditation practices into the daily routine, both of which have been shown to decrease sleep time latency.
But, the vast majority of American adults do regularly consume caffeine [19, 20], and through deductive reasoning I can presume that you, the reader, are likely a caffeine consumer, and that being the case, I happily to pass along the tip that the best buzz comes from cranking up the heat on your kettle.
Continued in PART 2: Tea temperature effects our mood and cognition by activating areas of the brain that regulate emotion-based behaviors such as empathy and kindness. The effect of water temperature on tea flavor profile. And, can hot tea actually cool you down? Yes and No… but… Yes it can. But not always.
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