Most people wait until they are thirsty to get a glass of water or another cold beverage. This can be a big mistake. By the time you feel thirsty, you are probably already dehydrated. In addition, experts say that as we age, our internal mechanisms for triggering thirst become less sensitive. About 70% of adults between the ages of 51 and 70 may be chronically under-hydrated, Nutrition Epidemiologist Jodi Stookey, told AARP Bulletin. This can increase the risk of Urinary Tract Infections, she said. Drink enough water so that you need to urinate every two to three hours, experts recommend.