When it comes to the number of trips you’re taking to the kitchen each day to refill your water glass, eight 8-ounce glasses a day has long been the standard advice. (Or even more, if you’re sweating it out at the gym.) But recent research shows that it’s actually a bit more complicated than that.
There’s actually no scientific evidence to back up the “eight glasses” guideline, according to this review of studies conducted in 2002. And any one-size-fits-all rule wouldn’t take into account the types of foods people are eating—since some foods are full of water. Someone who noshes on greens for lunch and enjoys watermelon as a snack has a more water-rich diet than someone who leans more toward meat and grains. In fact, Live Science points out, the average person gets 20 percent of his or her daily water intake through food.
Something else the “eight glasses” rule ignores: your coffee habit. And your smoothies, matchas, and kombuchas. Those sources count, too! And no, contrary to what you may have heard on the street—okay, the Internet—coffee does count as a hydration source.
The bottom line is that the number of glasses of water you’re drinking likely isn’t the best way to tell if you’re well-hydrated. (And neither is checking out the color of your pee—that’s a myth, according to sports dietitian Marie Spano, MS, RD.) Instead, make a mental note of how often you’re heading to the bathroom, she says. “You should be going every two to three hours,” Spano says. “And you should be producing a good amount of urine, not just a few drops.”