“The impact of coffee on hydration is a super common question,” says Ilisa Nussbaum, RD, clinical dietitian and nutritionist at Yale New Haven Hospital. “We always joke that nutritionists start each answer with ‘it depends,’ but it’s true for this question.” Here are a few ways to figure out exactly how your coffee habit is affecting your hydration levels. Studies have shown that drinking two to four cups of coffee (around an 8-ounce size cup—we’re not talking Venti here) had little impact on hydration for the regular coffee drinker. The caffeine in coffee is a diuretic, but with regular consumption of coffee, that diuretic effect actually decreases, having minimal impact on urine output. But don’t mistake this information as a free pass not to hydrate in general. While coffee itself isn’t too dehydrating, some frequent coffee drinkers should still hydrate in other ways. “Don’t let your caffeine intake impair your intake of straight fluids like water,” Nussbaum says. Coffee may not dehydrate you detrimentally, and it can even count toward your daily hydration—but it’s still imperative to drink enough water (and other more hydrating drinks) throughout the day. It’s important to pay attention to what you feel like when drinking coffee. For example, if you’re taking more trips to the bathroom (for number one or two), you may want to increase your fluid intake to replenish. And when a habitual coffee drinker goes sans caffeine for a few days, they should treat it more like they’re a casual drinker when they come back to it. “If you’re sick or recovering from an illness that left you caffeine-free for a few days, it’s a good idea to ease back into your coffee habit,” Nussbaum says. Of course, whenever you’re sick, it’s important to hydrate as much as possible. As for the decaf coffee drinker? Even decaf has trace amounts of caffeine, but it certainly has less of a diuretic effect than caffeinated. “The easiest way is to pay attention to what your body feels like when you drink coffee: its impact on your sleep and the number of times you’re going to the bathroom,” says Nussbaum.
