Fluid Balance

"In a normal diet, fluid is gained via food as well as in drinks. Along with water, most drinks such as tea, coffee, juices, and milk hydrate the body. However, alcoholic drinks may not contribute to body fluids as alcohol is a diuretic, a substance that increases the output of urine by the body. Caffeine, such as found in energy drinks, coffee, tea, and sodas, is also a diuretic. Caffeine has also been shown to have an impact on overall hydration, but significant amounts (300+ mg) are typically necessary to exhibit negative effects on the body. The amounts of water in different foods vary. Fluid loss occurs in various ways throughout the body with urination being the primary method. While the elimination of urine is periodic, the formation of urine constantly occurs. Urination not only removes excess water from the body but also rids the body of nitrogen-containing compounds and other wastes. A typical urine output is approximately 1.5 liters daily. Perspiration, or sweating, also removes fluid from the body. When body temperature rises, fluids are secreted through sweat glands to the surface of the skin. This fluid then evaporates, which has a cooling effect and reduces overall body temperature. A typical loss of water through sweating is about 0.5 liters per day. With hot weather, exercise, or physical activity, water loss can increase to 2 liters per hour. Because urine output and sweating are conscious and measurable methods of fluid loss, they are called sensible losses. The body can also exhibit fluid losses termed insensible losses. Insensible water loss is constantly occurring every minute of every day. These losses are neither consciously felt nor measurable. They include events such as breathing, because expelled breath contains moisture, and defecation, because feces also contain water. Water intake and water loss should be balanced in order to prevent dehydration and maintain a healthy body. The recommended daily intake is 10–13 cups of fluid from food and drink for adult males and 7–9 cups of fluid for adult females."