Water Intoxication

Being the most abundant and important compound to life, living organisms would not exist without water. Within the human body the majority of biological reactions require water to take place. Although it is possible for human survival without nutrients for up to several weeks, without water humans would die in a matter of days. In the human body, water makes up 60-70% of adult body weight. At cellular level water makes up between 70-95% of the mass of a cell. The amount of water in the human body is balanced. This balance is between water obtained from liquids consumed and food eaten, and water loss in urine during excretion or as water vapour in sweating. When the normal water balance in the body is disrupted, reactions within the body will be altered or cease. The human body uses several physiological control mechanisms which work together to maintain water balance.
Water within the human body is distributed between intracellular and extracellular fluids. The distribution of water between the two fluids is determined by osmotic pressure. Water can freely cross cell membranes keeping body fluids at an osmotic equilibrium. Equilibrium is reached when the osmotic pressure is equal in both intracellular and extracellular fluids. When there is excess water within the body, the kidneys absorb the water and secrete it was urine, this returns the water level to its osmotic equilibrium. The water and electrolyte balance within the body are closely linked4. The polar nature of water allows electrolytes such as sodium ions to dissolve. The level of sodium within the body affects the amount of water in and around body cells.
The body gets sodium from food and drink, and loses it in sweat and urine. Sodium plays an important role in water balance and is required to draw water through plasma membrane of body cells. This is because sodium and water move simultaneously, maintaining equilibrium of water and electrolytes across cell plasma membrane. The concentration of