Its early June in South Dakota and we are already experiencing extreme temperatures. IT IS HOT OUT THERE!

This extreme heat demands we revisit a discussion on hydration and our health.  Life doesn’t stop for leisure, work and recreational outdoor activities in the midst of this heat. So why is hydration so very important and how much is enough?

Water is essential for life. Without water, humans can only survive for a few days. Water comprises 75% body weight in infants to 55% in the elderly population and is essential for cellular homestasis and daily life functions.


Maintaining an adequate body hydration status is dependent upon precise cooordination between sensitive receptors in the body linked by neural pathways that integrate between the brain, kidneys, sweat glands and salivary glands. The brain detects deficits and excesses of water with precise sensitivity, sensing imbalances amounting to only a few hundred milliliters.  These brain sensors send  messages to salivary glands to regulate drinking and to the kidneys to regulate the formation of urine. Most consumption of water obeys signals of water deficit. BY THE TIME WE EXPERIENCE THIRST, WE ARE ALREADY FLUID DEFICIENT. 

With fluid deprivation older persons experience less thirst and subsequently drink less liquid when compared to younger persons. Older persons tend to drink insufficent amounts of water following fluid deprivation to replenish their body water deficit.  It is prudent that older adults learn to drink regularly when not thirsty and to drink fluids throughout the day.

Hydration status is critical to the regulation of body temperature.  Loss of fluid through sweat is an important cooling mechanism in hot climates and with physical activity.  If sweat loss is not compensated with fluid intake at regular intervals, especially with vigorous activity, hypohydration from sweating results in a loss of electrolytes, as well as reduction in plasma volume, and can lead to electrolyte imbalances and serious heat stress on the organs of the body. It is imperative that individuals working and or/exercising in hot climates hydrate themselves REGULARLY THROUGHOUT THE DAY, EVERY DAY, NOT JUST THE DAY OF THE ACTIVITY. 


During challenging athletic events, it is not uncommon for athletes to lose 6-10% of body weight in sweat loss. Exercise in hot conditions with inadequate fluid replacement is associated with hyperthermia, reduced stroke volume and cardiac output, decrease in blood pressure and reduced blood flow to muscle.  Athletes are encouraged to begin athletic activities in well-hydrated state and to drink fluids over and above their thirst threshold.


Dehydration affects cognition. Mild levels of dehydration can produce disruptions in mood and cognitive functioning.  With dehydration, alternations in concentration, alertness, short term memory, perceptual  discrimination, arthrimetic ability, visualmotor tracking, and psychomotor skills are noted.  Dehydration can produce delirium and delirium presenting as dementia in the elderly.


Inadequate fluid consumption can lead to constipation, decline in kidney function, blood pressure, blood volume and heart rate.  Water deprivation and dehydration can lead to development of headache, impaired concentration, and irritabilty.  Strong evidenc suggests that good hydration reduces the risk of kidney stones, exercise asthma,  and hyperglycemia in diabetic patients.


Recommendations for daily water intake is complex as hydration needs varies by age, body type, activity level, climate and underlying health conditions. Overall recommendations include:

  • Consumption of half your body weight in non-caffeinated fluids daily. This means, for a 150 pound person, they should consume at least 75 ounces of non-caffeinated fluid a day. Consumption should increase with activity, especially in hot climates.
  • Fluid consumption should be spread out regularly throughout the day, every day. Consistency is critical.
  • Caffeinated and alcoholic beverages can cause dehydration. For each caffinated or alcoholic beverage consumed, a non caffeinated/non alcoholic beverage should be consumed to replace the fluid lost.
  • Parents and coaches: allow frequent rest breaks in extreme heat to allow for adequate fluid consumption.