Q. I drink decaf coffee because I find that the caffeinated variety makes my throat dry. Green tea does not seem to dry my mouth or throat, but strong black tea does. Why is this? – Johanna, Australia

A. Like some fine wines, coffee and tea contain compounds that make your mouth feel dry. The sensation is called astringency, and when it’s major, your mouth actually can feel puckered. In wine and strong tea, it’s the tannins that can turn your mouth and throat into the Mojave (or, because you’re from Down Under, the Great Sandy Desert). In coffee, it’s the chlorogenic acid, which is beneficial to your health. Your green tea at sufficient strength probably would be just as drying.