The unofficial start of summer isn't actually Memorial Day—it's the time when everyone officially switches from hot to iced coffee. But even though summer is supposed to be the season of carefree strolls in the park, the adjustment to iced coffee can sometimes bring about a lot of uneasiness. (There's a reason people have made nearly 50,000 TikToks of the song "Drink Iced Coffee and Have a Panic Attack.") Is the caffeine content in iced coffee the culprit?
"The caffeine content in coffee drinks can sometimes vary greatly," Christine Beck, a healthcare provider in Pennsylvania, tells Bustle. “The strength (i.e. caffeine content) of any coffee depends on how you brew it and how much caffeine is in the cup.”
What is the difference between iced coffee and hot coffee?
If your iced coffee is brewed like hot coffee—hot first and then poured over ice—then it will have the same content and flavor as hot coffee. It gets diluted a bit as the ice melts, but other than that it's the same drink. But if your iced coffee is cold brew, the preparation method will be different. It's steeped for several hours, always cold, so it has less acidity than its hot-brewed-then-iced cousin and has a milder flavor. It's also more concentrated, which means you need to dilute it before drinking it (just like an Americano).
Because it brews so quickly and at such a high temperature, hot coffee is more acidic than cold coffee. Although your brain may require higher caffeine levels, this may not make your tummy too happy. Hot coffee, on the other hand, contains more antioxidants than cold coffee—these substances help prevent cell damage, so it's important to get them into your body whenever possible.
Does iced coffee have more caffeine than hot coffee?
Depending on which iced coffee you drink, there may not really be a difference in caffeine content. If you just pour hot coffee over ice, it still contains the same ingredients as hot coffee. Of course, you'll have less room in your cup for ice -- so overall, your 16 ounces of iced coffee will likely have less caffeine than 16 ounces of hot coffee. But that's only because the ice dilutes it, meaning there's less physical space, not because there's necessarily a chemical difference, Baker said. The ice and water content also makes iced coffee a slightly more hydrating drink than hot coffee, she adds. "If you add milk (or a milk alternative) to your iced coffee, this will further increase the hydration factor because milk and milk alternatives are mostly water," Baker adds.
But which one actually contains the most caffeine? "Caffeine is soluble in water, and the hotter the water you use to brew coffee, the more caffeine is extracted, which means you can extract more caffeine from the beans," Baker says. According to a study released by the American Chemical Society in 2020, hot coffee may actually have slightly more caffeine than cold coffee, but the difference isn't too extreme.
The answer to the ultimate question of which coffee can give you a pick-me-up is...it depends. When you need to brave your morning, order a cup of your favorite coffee—either way, you'll get a caffeine boost.
Research references:
Grim, M., Rao, N. and Fuller, M. (2020) The role of roasting on the chemical properties of cold brew coffee. American Chemical Society.
