Water is an essential nutrient for the human body. It plays a critical role in numerous physiological functions. Water acts as a building material, a solvent, a reaction medium and reactant, a transporter of nutrients and waste, a vehicle for thermoregulation, and as a supporter of joint health. (source) Water is also a key component of gut function. (source)
There are three primary sources of water: liquids, foods, and water that is metabolically produced within the body. Apart from water that is consumed, most liquids have a high water content (≥85%). Most foods are also composed of a significant amount of water, anywhere from 40 to 80 percent or more. Finally, water is a byproduct of the oxidation processes used to break down macronutrients.
Similarly, the body loses water through a variety of avenues. Most water is lost through urination. Evaporation through the skin is another avenue, both at rest and as body temperature increases. Water in the form of sweat seeps through pores in the skin and then evaporates to help cool the body. Finally, the body loses the rest of its water stores through either respiration or defecation. Depending on factors such as environment, body composition, age, and overall health, water loss can vary significantly.
Hydration is fundamental to overall health and performance. Optimal fluid balance can be maintained through monitoring water input and output, positively influencing multiple aspects of physical and cognitive function.
Physical performance is highly reliant on hydration status, as water plays an essential role in various physiological processes. Muscle hydration status, for example, has been linked to contraction speed and work capacity. (source, source, source) Hydration also aids in thermoregulation during physical exertion. (source) These processes are further impacted by hypohydration and its effect on cardiovascular function, which influences the delivery of resources like oxygen and nutrients to working cells throughout the body. (source)
Cognitive function is similarly influenced by hydration status. Proper hydration is essential for optimal brain performance, as the brain relies heavily on water to function efficiently. Even mild dehydration can impair attention and short-term memory, making it difficult to concentrate on tasks or retain information. Additionally, inadequate hydration can negatively affect mood, leading to feelings of irritability or fatigue, which further diminishes cognitive capabilities. Moreover, perceived energy levels are often influenced by hydration status; when the body is dehydrated, individuals may feel sluggish and less motivated, hindering overall productivity and mental acuity. (source, source)
Sleep performance is also impacted by hydration status. (source, source) Hydration status has been shown to affect duration of various sleep phases. (source) These consequences could have indirect effects on other aspects of physical and cognitive functioning.
Immune function biomarkers have been shown to be dependent on hydration status. (source) Dehydration may hinder immune function to the detriment of cognitive and physical performance.
Gut health and function rely on hydration status. (source, source) Specifically, water intake can determine gut microbiome and digestive processes. These negative effects could indirectly affect both cognitive and physical performance.
Common indications of hydration status are included in the table below:
Include salt Consuming salt promotes the concentration of sodium in the body, which plays a crucial role in hydration and supports a healthy fluid balance. (source, source, source) Recommendation Incorporate salty foods or add a pinch of salt to meals.
Prioritize proper hydration Consuming adequate amounts of water helps give the body the fluid it needs to replenish fluid levels throughout the body. (source, source) Recommendation Drink at least 0.5 oz of water per pound of bodyweight per day.
Supplement with electrolytes Consuming salts commonly found in electrolyte supplements promotes the concentration of sodium and other electrolytes in the body, which plays a crucial role in hydration and supports a healthy fluid balance. (source, source, source) Recommendation Supplement with a variety of electrolytes with at least 500 mg of sodium daily.
Hydration status plays a crucial role in cognitive and physical performance. An examination of associated biomarkers and patterns presents a clear picture of hydration status and appropriate interventions can then be prescribed.
Albumin Albumin is one of the most abundant circulating proteins in serum. It is made in the liver then transferred to the bloodstream. Albumin plays a significant role in mediating the movement of fluid in and out of the blood vessels and as a molecule transporter. (source) Its influence on fluid movement makes it crucial to hydration status.
