3. Coffee stays hotter when cream is added
And now for a little something about the science of coffee. Adding cream to your brew actually keeps it warmer longer, even though the initial addition of cold cream cools it somewhat.
Overall, coffee with cream cools 20% slower than black. That’s true for a couple of reasons. First, the darker the beverage, the faster it gives off heat. And second, the more viscous the beverage (coffee with cream is thicker than black coffee), the slower it gives off heat.
There is also some evidence that the caffeine in coffee with a dairy additive (milk or cream) is absorbed more slowly by the body. That can decrease the zing you get from it. However, it’s not decreased by much, and other things play a greater role in how quickly caffeine is metabolized, including how much fiber you also have in your stomach.