Only a small percentage of people consume sufficient fluids daily, however the optimal daily intake of an adult should be at least 2 liters. When our body lacks fluids, it sends such signals as fatigue, indigestion, headache, etc. The role of water in our body is so fundamental that if its quantity is only 4% short leads to severe water deficiency. Under optimal conditions the body needs at least 2.5 liters of water daily. On average, the water balance of our body can be described as follows:
Water gain: through fluid intake 1500 ml, food intake 750 ml, and an extra 250 ml. after metabolic water production, that is a total of 2500 ml.
Water loss: through urine excretion 1600 ml, 100 ml through the gastro-intestinal tract (faces), and 800ml through breathing and transpiration, that is a total of 2500 ml.