The average woman needs approximately nine cups (72 fluid ounces) of fluid per day to stay well hydrated in a sedentary state. That includes all types of fluids from all beverages and foods. You need additional fluid intake if you exercise, diet or travel; if you are ill, pregnant or nursing; or if you live at high altitude or in a hot, humid environment. Research on water in particular has shown that people who drink a minimum of five to six cups of H2O per day have a statistically significant reduced risk of many types of cancer, heart attack and stroke when compared to those who drink only two cups or less each day. In these studies, only flat, sparkling and unsweetened flavored water counted as water.
Susan Kleiner, PhD, RD, is an international columnist and a speaker on the subjects of nutrition, sports and fitness.