Possibly the most underemphasized aspect of sports nutrition, hydration can make or break an athlete’s performance.  While fuel depletion during exercise can impair performance, inadequate water not only impairs exercise capacity, but can create life threatening disturbances in fluid balances and core temperature.  With as little as 1% of body weight lost in fluid, athletes can experience thirst, fatigue, and weakness.(1)  Thirst drives a person to drink, but it can actually lag behind the body’s need.  When too much water is lost from the body and not replaced, dehydration develops.  Dehydration refers to an imbalance in fluid dynamics when fluid intake does not replenish water lost.  On the flip side, water intoxication occurs with excessive water intake or kidney disorders that can reduce urine output.  In healthy individuals, dehydration is more common than water intoxication, but appropriate water balance is crucial to optimal performance and ultimately survival.  

Water and Body Fluids

Water constitutes about 60 percent of an adult’s weight and it is the medium in which all life processes occur, including:

• Carrying nutrients and waste products through the body
• Maintaining the structure of large molecules
• Acting as a solvent for minerals (i.e., sodium and potassium) and other small molecules
• Acting as a lubricant and cushion
• Maintaining blood volume
• Helping the body regulate temperature

Every cell in the body contains fluid specific for that cell called intracellular fluid, and around it is extracellular fluid.  These fluids continually lose and replace their components, but the composition of each compartment remains remarkably constant.

Because an imbalance can be devastating, the body continually adjusts water intake and excretion as needed.  This type of balance is referred to as homeostasis.  

Fluid maintains blood volume, which influences blood pressure. The homeostatic balance of fluids and solutes in the body is carefully regulated by the kidneys with assistance from several hormones including antidiuretic hormone (ADH) and aldosterone.  The primary solutes that are involved in maintaining fluid balance are sodium, potassium, proteins, and glucose.  Adequate intakes of water and electrolytes maintain hydration levels and regulate fluid shifts between the intra- and extra-cellular compartments.

Tags: importance of it, Nutrition, water

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