The Health Effects Of Iced, Room Temperature & Hot Tea, According To Science
What temperature do you take your tea? The question has to do with a lot more than just taste; the health effects of iced, room temperature, and hot tea can each be very different. Your choice of piping-hot tea, sun tea, or tea you drink after leaving it on the counter for an hour has an impact on antioxidants, body temperature, metabolism and even, according to some studies, cancer risk. There's no definitive answer on which is the 'best' temperature for tea; it seems that every temperature range has its own pros and cons.
Tea is traditionally steeped in water to release compounds that create its color and tasty flavor, and there's a lot of variation in tea consumption worldwide. Some teas are traditionally drunk extremely hot. Black tea leaves can also be exposed to boiling water without a problem, but green tea leaves will be scorched and need to be added to cooler water to avoid a nasty bitter taste. Queen Elizabeth II reportedly likes her black tea cooled by a little cream, while statistics indicate that iced tea is becoming more popular, with consumption spiking from 37 million liters worldwide in 2016 to a predicted 41 million liters by 2021. However you choose to take your tea, here are the benefits — and the drawbacks.
1. Temperature Affects Antioxidant Levels In Tea
Tea is famous for its antioxidant properties, but the amount that actually make it into your body may depend on how hot you brew it — and what kind of tea you like. A 2015 study published in the Journal of Food Science found that antioxidant levels differed in tea depending on the type of leaf used and how hot it was brewed.
White tea showed the most antioxidants when left to steep for a long time, regardless of whether the water was hot or cold. For green tea, antioxidants peaked when it was steeped for a long time in cold water, while black tea produced the most antioxidants when it was brewed for a short time in very hot water. Oolong tea, which is semi-fermented, was tested in a study in 2015 and found to be very sensitive to high temperatures, so if you're maximizing antioxidants, it's a good idea to infuse it cool or cold.
However, if you do love your green tea hot, there's hope: a study of Turkish green tea tested 75, 85, and 95 degree Celcius brews, and found that 85 degrees for three minutes maximized helpful antioxidant levels. It also depends on how you're taking the tea. A 2015 study found that when you're using whole leaves for brewing green or white tea, you get maximum antioxidants from cool water, but when you're using tea bags — which normally use broken-up, milled leaves — you get the most antioxidants from hot water.
2. Very Hot Tea May Increase Cancer Risk
There's been a discussion for a while in scientific circles about whether drinking very hot tea can affect cancer risk. A study in 2018, for instance, found that there could be a link between cancer and very hot tea drinking — but only in people who also smoke and drink alcohol, which are both known to raise cancer risk. Since 2016, the International Agency for Research on Cancer has defined drinking very hot beverages as a potential carcinogen, though the studies that determined that result mostly focused on maté, which is traditionally drunk at scorching temperatures.
More recently, a study published in the International Journal of Cancer in 2019 studied 50,045 Iranians between 2004 and 2008, and found that preferences for extremely hot tea and drinking hot tea very soon after boiling were both associated with a 90 percent increase in risk for developing esophageal cancer. However, more work needs to be done to establish whether this is just an association, or a definite case of cause and effect.
3. Hot Tea Actually Make Us Friendlier
A study from 2008 sheds light on why you might feel better when holding your hot tea in the mornings; heat in beverages appears to make humans feel warmer towards others. People who held a warm beverage (in the case of the experiment, coffee) and were asked to judge somebody else gave much warmer judgements about them — around an 11 percent improvement — than if they were asked to do it while holding an iced drink. Psychologically, it seems that the experience of holding and having a hot beverage raises our ideas of comfort and internal warmth, in turn apparently shifting our perspective about others. Iced tea? Not so great.
4. Hot Tea Helps Cool You Down In Hot Weather, While Cold Tea Might Be Less Effective
How do drinks actually affect our body temperature? It may sound counterintuitive, but hot drinks can help a little on very hot days by increasing our sweating. “If you drink a hot drink, it does result in a lower amount of heat stored inside your body, provided the additional sweat that’s produced when you drink the hot drink can evaporate,” researcher Ollie Jay told Smithsonian Magazine in 2012. "When you ingest a hot drink, you actually have a disproportionate increase in the amount that you sweat." And that will lead to cooler body temperature overall.
What about cold iced tea? Neuroscientist Peter Poortvliet explained for The Conversation in 2015 that drinking something cool does in fact make us feel colder — but this doesn't last very long. "A small amount of liquid will lose its cooling effect quite quickly as it gets warmed up by the surrounding organs. And large amounts of cold liquids will cause blood flow to slow, making heat transport less effective," he noted. Long-term, cool drinks help us feel better in hot weather because they replace water lost by sweat, not because they do any real internal cooling.
5. Cold Or Room Temperature Infusion Is Best For Extracting Maximum Goodness
Tea doesn't just contain antioxidants; it's got a host of other compounds and ingredients that are meant to help the body. And if you want to maximize those benefits, science says cold and room temperature infusions may be the best way to do it. "Hot infusion showed rapid extractive power, but relevant compound degradation. On the contrary, cold infusion extracted higher level of healthy molecules," explained a study in 2015. Cold infusion, it found, doubled levels of bioactive compounds like gallic acid and epigallocatechin gallate in green and black teas.
This works for white teas too. According to a study in 2014, cold infusions of white tea over time produced the highest levels of antioxidants, and a study in 2015 revealed it was also best for levels of bioactive compounds in white tea in general.
However, short infusion in hot water does have benefits, like minimizing bitterness in teas, so if you love your hot tea, don't fret. It could be worth trying out cold infusions as a potential new way to enjoy your favorite beverage.
Tea is known for its health effects, but you may not have known that the temperature you take it at may have an impact, too. Drink up.