Water is an essential nutrient, just like the nutrients in food. Your body is made up primarily of water, which accounts for 50 to 80 percent of your body weight. Your requirement for water varies, depending on such factors as the temperature and humidity or your activity level. Water loss through perspiration during physical exertion can increase your body’s need for water dramatically. Having diarrhea also can cause excess water loss from your intestines, so it’s important to drink plenty of fluids when you have a bout of diarrhea.
In general, thirst is the best indicator that you need water. Don’t quench your thirst with caffeinated soda or alcoholic beverages because caffeine and alcohol will only dehydrate you further. Older people may find that their thirst sensation has become dulled. If you are an older man, remember to drink at least eight glasses of water and other fluids, 8 ounces each, every day, regardless of whether you are thirsty, and especially in hot weather.