However, according to Dana Cohen, M.D., integrative medicine physician and co-author of Quench, it’s time we take a closer look at the pervasive gold standard. “Eight glasses of water a day—it comes from nowhere,” she says on the mindbodygreen podcast. Because let’s be honest: How can two people with completely different body types, environments, and lifestyles require the same amount of water? “It doesn’t make any sense,” she adds.