Water is an important nutrient vital for a variety of bodily functions and processes including hydrating and lubricating cells, removal of waste products, carrying nutrients, regulating body temperature, reducing fluid retention, and helping to keep bowel functions normal. According to Wake Forest University researchers, people do not get enough pure water in their diet. To calculate how much water you need take your weight in pounds and divide by two. The result is the number of ounces of water you should drink a day. So a 100- pound woman needs to drink 50 ounces of water each day — just a little more than four 12-ounce glasses, or three bottles of water (which usually are 500 milliliters or 16.9 ounces.) A 175-pound man would need five bottles of water.