“Caution: Contents Hot!” An omnipresent warning label these days, serving to remind us of the latent risk of a cup of hot tea or coffee. As a hapless woman found out the hard way in a McDonald’s parking lot in 1994, hot coffee causes serious burns when spilled. The lawsuit following this incident settled in favor of the victim, who received one full day of McDonald’s coffee sale profits (over two million dollars initially, however later lowered to a six-figure payout). Years later, you can walk into any McDonald’s and find that the coffee is the same temperature (190 Fahrenheit) that it was when it incited the “ouch hot coffee incident of ’94.” All that has changed is the addition of a warning label, and that is primarily because people really enjoy their drinks hot. But what is so good about a molten-hot beverage? And why am I not crazy for wanting my tea at scalding hot temperatures? (truly scalding, check the graph).
It turns out that risking potential burn damage can reap great benefits for the brave consumer. For drinkers of hot tea, these benefits range from high antioxidant capacity, to more caffeine, to even a greater sense of empathy for strangers, and more. Let’s dive into a few of these piping hot upsides of preparing and consuming your tea hot.
More Antioxidant Power
The capacity of tea polyphenols to combat oxidative damage in our bodies is a well-known benefit of regular tea consumption. Founder and CEO of The Tea Spot, Maria Uspenski, gets into the weeds on tea’s anti-oxidant effects in her book Cancer Hates Tea. Maria’s view is in line with most modern scientists, who purport that cancer is caused at least partly by excess intake of carcinogens (or free radicals) as a result of unhealthy environment or lifestyle conditions . Due to an abundance of antioxidant compounds, tea combats and neutralizes harmful free radicals. But, these polyphenol antioxidants are extracted from tea leaves most efficiently at specific temperatures. Finicky compounds as they are, scientists have sought to understand how exactly tea polyphenols can be extracted most effectively from the leaf. Here are findings from several recent studies measuring the effect of water temperature on polyphenol extraction.
- 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, compared to room 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 antioxidant power [7,8,9].
- Two studies showed greater antioxidant extraction for cold water than hot water, but only after infusion over several hours [17,18].
There’s a brief look into the pandemonium that this type of data can sometimes be. Despite the variable data, hot water extracted antioxidants much more efficiently than tepid or cold water in time frames under two hours. If you’re looking for a quick hit of antioxidants, hot infusion is the way to go.
Caffeine is a more stable compound than tea polyphenols, meaning it’s extraction is more consistent than the polyphenol madhouse. Hot water and long infusion times lead to greater caffeine extraction rates [6,14]. I snipped a data table from a recent study that measured caffeine extraction 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). Here is some nice clean data for the whole family to enjoy…
As most caffeine consumers might agree, high doses of caffeine is all about timing (and personal tolerance). If you’re trying to kick start your morning with a pekoe pick-me-up, a high temperature infusion will give you the caffeine-rich beverage you’re looking for. If it’s 10pm and you’re watching reruns of Lost with the kids for educational purposes, avoid the high-temperature infusion. Regular caffeine intake is not always recommended, as it remains a matter of debate within the scientific community in terms of its effect on human health (so does Lost). But, if you’re one of 89% of American adults that regularly consumes caffeine, try the high heat option to get your buzz on [19,20].
Warm Tea, Warm Heart
Research out of The Tea Spot’s backyard, at the University of Colorado at Boulder found that judgment of another human’s character can be influenced by the temperature of the drink we are holding.
CU Boulder professor, Lawrence E. Williams, conducted a study in which a group of undergraduates were asked to answer a series of hypothetical questions about a fictitious person’s personality traits . But first, on an elevator ride to the lab, a busy lab worker overloaded with a steaming hot or icy cold coffee cup, two textbooks and a clipboard asked the participant to briefly hold the cup while they sorted through some papers. Results showed that participants who held the hot coffee were more likely to later judge the fictitious person as more generous or caring, (i.e. ’warm’ personality traits), and less likely to do so if they had held the iced coffee.
In a follow-up study, participants held heated or frozen therapeutic packs as part of a product evaluation study and were then told they could receive a gift certificate for a friend or a gift for themselves. Those who held the hot pack were more likely to ask for the gift certificate for their friend, while those who held the frozen pack tended to keep the gift for themselves. As Yale University psychologist and co-author of the study, John A. Bargh, explained,
“It appears that the effect of physical temperature is not just on how we see others, it affects our own behavior as well. Physical warmth can make us see others as warmer people, but also cause us to be warmer – more generous and trusting – as well.”
The mechanism for this phenomenon may lie in a portion of the brain’s cerebral cortex called the insula, or insular cortex. The insula is believed to be involved in consciousness, and play a diverse role in many important human functions. These functions include regulating both emotion (particularly empathy) and bodily homeostasis (including body temperature). Thus, it may in this region of the brain that warm emotions and physical warmth, overlap.
Though more research is needed, this data can provide another reason to offer warm tea to your significant other before telling them about the Christmas gift you bought yourself on layaway (it was a killer deal and you needed it anyway, and you hardly ever treat yourself).
High Heat, Bold Flavor
Most tea drinkers have been told at some point that white tea needs the lowest infusion temperature, then green tea, then oolong, then yada yada. I believe this paradigm is off, particularly with white tea. Look at one study where 12 highly-trained panelists tasted white tea infused at various temperatures .
Results showed that brewing at 70 °C/158 F (the recommended temperature for white tea) only reached 13% of likes, similar to that obtained for 80 °C/176 F (14%). An increase in preference was obtained with the recommended temperature for green tea (27% at 90 °C/194 F) but infusion in boiled water (98 °C/ 204.8 F) was preferred by 43% of consumers. The reason had to do with perception of the taste as “strong.” Hot water extracts more total compounds, creating a “stronger” taste, which people typically enjoy. If you have whole-leaf tea, and you enjoy a robust flavor, try turning up the heat, even if conventional tea culture cautions against it.
Fun fact: Maria Uspenski and I were in Hangzhou, China, in November drinking white tea that had been cooked over a stove (decocted). In other words, tea leaves sitting in actively boiling water for 10-15 minutes. The flavor was fantastic… rich and sweet, molasses notes in the nose, long, smooth finish, and a liquor that was vibrant golden/amber. A white tea. Boiled. Just saying.
Hot Tea, Cool You Down?
Strangely enough, consuming hot beverages can cool you down on hot days. The heat from a warm cup of tea goes straight to your core, causing your body to think it’s hotter than it really is, eliciting a sort of over-heating overreaction. The body sweats (sweating is key) and diverts hot blood to your skin, which can cause you to lose more heat than you initially gained from the hot tea.
This concept was put to the test in a 2012 study, in which nine males cycled for 75 minutes with body heat sensors attached to their bodies. Total body heat retention was lowest when they consumed 50 degree Celsius (122 F) water (the warmest temperature measured in the study) compared to 1.5, 10, and 37 degrees (34.7, 50, 98.6 Fahrenheit, respectively) .
The explanation boils down to good ol’ sweat. When sweat evaporates, the energy stored as heat is removed from the body. BUT, you need to let the sweat evaporate. If you wipe the sweat away, or it’s too humid out, the sweat won’t evaporate, and you won’t lose any heat.
In the study mentioned above, human participants were cycling on stationary bikes directed at large fans, which allowed sweat to evaporate easily. In that light, we can view this hot-tea cool-down trick as viable mostly for outdoor athletes, or people with access to a breeze, loose clothing, and relatively dry air. If you’re starting to feel warm under your blazer at the cocktail party, maybe don’t reach for a cup of boiling hot Assam to cool you down (but hey, maybe I will be the sweaty guy enjoying a great cup of tea, you do you).
There you have it! More antioxidants, more caffeine, more heart, more flavor, more… sweat. Feel free to comment here with any questions, comments, thoughts, etc. Cheers and thanks for reading!
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