SUNDAY HEALTH: Water Balance in Humans Body Dr. Ali A. Mzige Daily News; Sunday,October 28, 2007 @00:03 WATER accounts for about one half to two thirds of an average persons weight. Fat tissue has lower percentage of water and women tend to have more fat, so the percentage of water in the average woman is lower (52 to 55%) than it is in the average man (60%). The percentage of water is also lower in older and obese people. A 70 kilogram man has about 45 litres (10 gallons) of water in his body: 6-7 gallons inside the cells, 2 gallons in the space around the cells, and slightly less than 4.5 litres (1 gallon) (or about 10% of the total amount of water) in the blood stream. The body regulates the amount of water in each of these areas. Water is moved as needed to keep the amount in each area relatively constant, thus enabling the body to function normally. Water intake must balance water loss. To maintain water balance and -- to protect against dehydration, the development of kidney stones, and other medical problems--healthy adults should drink at least 1.7 litres (1700 cc) to 2.2 litres (2200 cc) a day. Drinking too much is better than drinking too little, because excreting excess water is much easier for the body than conserving water. However, when the kidneys are functioning normally, the body can handle wide variations in fluid intake. The body obtains water primarily by absorbing it from the digestive tract. Additionally, a small amount of water is produced when the body processes (metabolizes) certain nutrients. The body loses water primarily by excreting it in urine from the kidneys. Depending on the bodys needs, the kidneys may excrete less than 560 cc or up to several gallons of urine a day. About one litre (1000cc) of water are lost daily when water evaporates from the skin and is breathed out by the lungs. Profuse sweating--which may be caused by vigorous exercise, hot weather, or a fever can dramatically increase the amount of water lost through evaporation. Normally, little water is lost from the digestive tract. However, prolonged vomiting or severe diarrhoea can result in the loss of a gallon (4.5 litres) or more a day. Usually, a person can drink enough fluids to compensate for excess water loss. However, a person may be unable to drink enough fluids to compensate for water loss caused by prolonged vomiting or severe diarrhoea, and dehydration may result. Also, confusion, restricted mobility, or loss of consciousness can prevent a person from being able to drink enough fluids. Mineral salts (electrolytes), such as sodium and potassium, are dissolved in the water in the body. Water balance and electrolyte balance are closely linked. The body works to keep the total amount of water and the levels of electrolytes in the blood stream constant. For example, when sodium level becomes too high, thirst develops, leading to an increased intake of fluids. In addition, a hormone secreted by the brain in response to thirst causes the kidneys to excrete less urine. The combined effect is an increased amount of water in the blood stream. As a result, sodium is diluted and the balance of sodium and water is restored. When the sodium level becomes too low, the kidneys excrete more urine, which decreases the amount of water in the blood stream, again restoring the balance. How should we avoid dehydration? Dehydration is a deficiency of water loss in the body. Dehydration is particularly common in older people, because their thirst centre does not function as well as a younger persons. Therefore, an older person may not recognize as he is becoming dehydrated. Certain disorders such as diabetes mellitus (kisukari), diabetes inspidus (excessive urination and severe thirst but no sugar in urine--a disease that needs special investigation) can increase excretion of urine and thereby lead to dehydration. Dehydration may lead to low blood pressure and death if not corrected like in diarrhoea and vomiting due to cholera. Kidneys, liver and brain can be damaged if dehydration is not corrected. Treatment Prevention is better than cure. Adults should drink at least 6 glasses of fluids daily (not alcohol). Fluid intake should be increased on hot days. Exercise, fever, and hot weather increase the bodys need for water. For mild dehydration, drinking plenty of water may be all that is needed. If electrolytes (especially sodium and potassium) are lost, they must be replaced. Flavoured sports drink if available; have been formulated to replace electrolytes lost during exercise. These drinks can be used to prevent dehydration. Drinking plenty of fluids and consuming a small amount of salt (for example, by taking salt tablets or drinking a sports drink) during or after exercise works as well. Before exercise people with heart or kidney disorders should consult their doctors about how to replace fluids. More severe dehydration requires treatment by a doctor. If blood pressure becomes very low, a solution containing sodium chloride is usually given intravenously. The intravenous solution is given rapidly at first and then more slowly as the persons physical condition improves. Please note, coconut juice (madafu) is very good source of potassium, drinking coconut juice during dehydration especially due to diarrhoea can save your life. Children who drink kerosene from bottles of soda like Coca cola and the like, sometimes take them for mixed identity as soda but some due to being thirsty. Encourage children to drink water during hot seasons and during meals, avoid soda drinks.