But water lovers got a jolt recently when we heard that a new report had found that the benefits of drinking water may have been oversold. Apparently, the old suggestion to drink eight glasses a day was nothing more than a guideline, not based on scientific evidence Reasons to make sure you're drinking enough water or other fluids every day: Drinking Water Helps Maintain the Balance of Body Fluids . Your body is composed of about % water. The functions of these bodily fluids include digestion, absorption, circulation, creation of saliva , transportation of nutrients , and maintenance of body temperature . "Through the posterior pituitary gland, your brain communicates with your kidneys and tells it how much water to excrete as urine or hold onto for reserves," says Guest, who is also an adjunct professor of medicine at Stanford University. When you're low on fluids, the brain triggers the body's thirst mechanism. And unless you are taking med