Nicola Roy, a journalist with the Spare Time team, conducted a personal experiment during the ongoing UK heatwave to determine whether hot or iced coffee is more effective at cooling the body. The test was prompted by scientific claims that hot beverages can actually lower body temperature by inducing sweating.
Hot Coffee Theory
Researchers from the University of Ottawa's School of Human Kinetics suggest that drinking a hot coffee or tea encourages the body to sweat more, which in turn helps regulate temperature through evaporation. According to this theory, the cooling effect from sweating outweighs the heat absorbed from the drink itself.
Roy began her experiment with a steaming hot double flat white at 9:30 am, when the flat was already uncomfortably warm. Despite the scientific rationale, she found that the hot coffee did not induce sweating; instead, it made her feel warmer. "The hot coffee didn't quite induce sweating, though it certainly warmed me up — far from ideal given it was already stifling hot," she reported.
Iced Coffee Test
After the disappointing hot coffee experience, Roy switched to an iced coffee, filling a glass with ice, adding an espresso shot, and mixing in oat milk. From the first sip, she felt immediate relief. "Even from the very first sip, I immediately felt more relief from the heat than with the hot coffee," she noted. The cold glass itself provided a comforting sensation, and she found the drink far more refreshing overall.
Roy acknowledged that residents of warmer European nations often prefer hot coffee to cool down, but she concluded that this method may not suit everyone, especially in Scotland. "Perhaps we Scots haven't adapted to this approach yet, as I'll be opting for the chilled drinks while the heatwave continues," she said.
